Pharmacology Fundamentals PDF

Pharmacology Fundamentals **Week One** When administered to a living organism, drugs produce a biological effect. Drugs can be: L\> Synthetic Chemicals L\> Natural Chemicals - Plants - Animals - Microorganisms \*Substances that are released by physiological mechanisms are not drugs, un...

Pharmacology Fundamentals **Week One** When administered to a living organism, drugs produce a biological effect. Drugs can be: L\> Synthetic Chemicals L\> Natural Chemicals - Plants - Animals - Microorganisms \*Substances that are released by physiological mechanisms are not drugs, unless they are also administered (e.g., Insulin) Areas of pharmacology include: **Field** **Pharmacological Branch** -------------------------------- ---------------------------- Psychology Psychopharmacology Clinical Medicine Therapeutics Clinical Pharmacology Veterinary Medicine Veterinary pharmacology Biotechnology Biopharmaceuticals Pathology Toxicology Chemistry Medicinal Chemistry Genetics Pharmacogenetics Genomics Pharmacogenomics Epidemiology Pharmacoepidemiology Health Economics Pharmacoeconomics **Week Two** **Pharmacokinetics** is the study of how the body interacts with the administered substances for the duration of exposure. **Pharmacodynamics** is the study of what drugs do to the body and how they do it. There are four stages of drug disposition: 1. Absorption 2. Distribution 3. Metabolism 4. Excretion The most fundamental principle of pharmacokinetics is drug absorption, defined as the transportation of an unmetabolized drug from the administration site to the body's systemic circulation. Regardless of the absorption site, the drug must cross a cell membrane in order to reach the systemic circulation. There are several mechanisms of drug transportation and absorption, including: L\> Passive Transport: the movement from an area of high concentration to low concentration - Passive diffusion is the most common mechanism of absorption for drugs. Passive diffusion can occur in an aqueous or lipid environment. Aqueous diffusion occurs in the aqueous compartment of the body, such as through the aqueous pores in the endothelium of blood vessels.\ Drugs bound to albumin or larger plasma proteins cannot permeate most aqueous pores. - Lipid diffusion occurs through the lipid compartment of the body. Lipophilicity is a critical factor for drug permeability due to the number of lipid barriers that separate body compartments and the lipid bilayer that exists in all cell's plasma membrane L\> Another mechanism of absorption is via carrier-mediated membrane transporters. Numerous specialised carrier-mediated membrane transport systems are in the body to transport ions and nutrients, particularly in the intestine. Such systems include: - Active Diffusion is an energy-consuming system essential for GI absorption and renal and biliary excretion of many drugs. The process facilitated the absorption of lipid-insoluble drugs. It also allows the movement of drugs from regions with low drug concentration to regions with higher drug concentrations. - Facilitated diffusion does not require energy and does not enable the movement against a concentration gradient. An example of this system is the organic cation transporter 1, which facilitates the movement of drugs such as metformin. One of the most influential physicochemical variables affecting drug absorption is the drug solubility and the effect of pH and pKa. Where most drugs are weak acids or weak based in solutions both ionised and unionised forms. Ionised drugs are hydrophilic and cannot cross the cell membrane. Unionised drugs are lipophilic and can penetrate the cell membrane through simple diffusion. Weakly acidic drugs are easily absorbed in an acidic environment such as the stomach, meanwhile weakly basic drugs are not absorbed until they reach the higher pH in the small intestine. page10image402904880 Some other factors affecting a drugs absorption include: - Lipid solubility - Surface area - Gut content - GI transit time - Gastric emptying rate - Blood flow to site of administration - Drug interactions \***In most cases, approximately 75% of a drug given orally is absorbed in 1-3 hours. However, we must consider factors that may affect absorption** pH changes in different body compartments can also influence the degree of ionisation and consequently a drug's absorption rate. If a drug is a weak acid, it will be more ionised at a higher pH like urine and will be more unionised at a lower pH such as gastric juice. Whereas a weak basic drug will be more ionised at a lower pH and more unionised at a higher pH. If the pKa of the drug is **less than the pH of the body compartment**, it will be predominantly **ionised or deprotonated**. If the pKa of the drug is **more than the pH of the body compartment**, it will be predominantly **unionised or protonated.** Routes of drug administration include - Oral - Sublingual = placement of drug under the tongue - Rectal - Application to other epithelial surfaces (skin, cornea, vagina) - Inhalation - Injection: Most drugs require absorption for activity. Several drug and physiological factors affect the rate and degree of absorption. For example, - Lipid solubility - Molecular weight - pKa - Surface area - Gut content - GI transit - Blood flow to site of administration - Drug interaction Pharmacokinetics focuses on concentrations of a drug in the blood plasma -- denotes Cp. This is useful during drug development and to determine individualised dosage of drugs. These parameters can be used to adjust dose regiment to achieve a desired plasma concentration. The Area under the curve is a measurement of plasma concentration of a drug over time. Cmax denotes the maximum plasma concentration reached and Tmax denotes time to reach Cmax. Bioavailability is another parameter that represents the fraction of the dose which proceeds unaltered form the site of administration to the systemic circulation. If 100% of the dose enters, the bioavailability is 1.0. AUCpo po = Per oral Bioavailability = \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- AUCiv iv = intravenously Low drug oral bioavailability is mainly due to first pass metabolism and low absorption. First pass metabolism describes presystemic drug elimination that can occur in the gut wall, portal vein or liver. Bioavailability only considers the total fraction of a drug that reaches systemic circulation and neglects the rate of absorption. Interindividual variability is mainly caused by change in: - Enzymatic activity of gut wall or liver - Gastric pH - Intestinal motility Binding of drugs to plasma proteins also affects drug distribution. - Albumin (mainly acidic drugs) - A1-acid glycoprotein Volume distribution is the volume of fluid into which a drug is distributed. Factors that affect the movement of drugs include: - Permeability across tissue barriers - Binding within compartments - pH partition - Blood flow to the tissue Hydrophilic drugs are likely to have a lower Volume distribution whilst lipid soluble drugs (e.g.., tricyclic antidepressants) have higher Volume distribution. If a drug is highly acidic, it has a higher affinity to albumin molecules and consequently is more likely to bind to albumin plasma proteins and remain in the plasma membrane. Amount of drug in the body (mg) Volume Distribution = \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- Plasma concentration of drug (mg/L) VD can be in L or L/Kg \*when using L/kg, divide the Litres by 70kg Acid Base  Unionised drugs cross lipid biological barriers better than ionised drugs. If an acid (HCl) is added to the equilibrium it moves to the right. If an alkali (NaOH) is added, then the OH- group and H+ ions neutralise each other to form water, and the equilibrium moves to the left. **Week Three** Drug elimination is when a drug is irreversibly removed from the body. This can happen via metabolism or excretion. A drugs half-life is the time taken for the blood plasma concentration to decrease by half. The main organs involved in drug elimination are the liver and the kidneys. Drug metabolism or biotransformation is the process of chemical modification of drugs usually by enzymatic reaction within the body. **Catabolic Reaction** = breakdown reaction **Anabolic Reaction** = synthesis reaction **Prodrug** = a drug that is inactive when taken and needs to be metabolised for it to become active **Active drug =** a drug that takes effect directly without needing to be metabolised first. Metabolism results mostly in the formation of more water-soluble compounds for urine excretion **Phase 1 Reaction - Functionalisation** These are non-synthetic **catabolic** reactions that introduce a reactive (polar functional) group. Oxidation/reduction/hydrolysis = more water soluble. Metabolites are sometimes more toxic or carcinogenic than the parent drug. Some drugs must undergo stage one metabolism to exert a therapeutic effect e.g, codeine morphine. These are called **prodrugs.** The enzymes involved in phase 1 reactions are the **cytochrome P450 enzymes**. These enzymes are mainly present in the liver. In the cell, they are embedded in the **endoplasmic reticulum** **P450 Monooxygenase system** Very large family of enzymes that differ from one another in: - Amino acid sequence - Sensitivity to inhibitors and inducers - Specificity of catalysed reaction Different CYPs have subtract specificities, however, overlapping is common - CYPs 1A2, 3A4, 2D6 and 2C19 are responsible for over 50% of small-molecule drug metabolism **Phase 2 Reaction - Conjugation** These are synthetic **anabolic** reactions. In phase 2 metabolic reactions, an endogenous molecule is attached to a drug molecule. This increases the hydrophilicity of the drug. Most common is glucuronidation The enzymes involved in phase 2 reactions are **Transferases**. \*Phase 1 and 2 reactions may be **sequential** or may occur **simultaneously.** **Factors affecting drug metabolism**   - Genetic factors: genetic variations to liver enzymes can have profound effects on the level of certain drugs in the body - Induction and inhibition of cytochrome P450 enzymes - Concentration-dependent biotransformation - Disease-induced factors Most drugs are excreted through the kidneys either unchanged or as polar metabolites. Most drug metabolites are inactive however 25-30% of drugs are mainly excreted at the active form. For these drugs, renal impairment causes drug accumulation and increased chance of toxicity. Other routes of excretion include: - Hepatobiliary system - Pulmonary system - Sweat, saliva, tears - Breast milk There are three important processes that can affect drug renal excretion: 1. Glomerular filtration = drugs cross glomerular filter freely, unless highly bound to plasma protein 2. Active tubular secretion = Basic drugs in their protonated form are transported by organic cation transporters (OCTs) while acidic drugs are transported by organic anion transporters (OATs) 3. Passive tubular reabsorption = lipid soluble drugs are not efficiently excreted in the urine because they are passively reabsorbed along the water by diffusing across the tubular barrier. Similarly, to renal tubule, drugs are transported from the plasma to the bile in hepatobiliary excretion. Organic cation transporters, organic anion transporters and p-glycoproteins are important for this transport as well. After reaching the small intestine drugs can be reabsorbed to be excreted by the kidneys and recirculate until completely excreted in the urine or faeces. Glucuronide conjugated drugs can be metabolised in the intestine, and the free drug reabsorbed **Factors affecting drug excretion** - Altering protein binding, and hence filtration - Inhibiting tubular secretion (e.g., Probenecid inhibits the secretion of penicillin) - Altering urine flow and/or urine pH (e.g., diuretics and drugs that alkalinise or acidify the urine  Rate of elimination is directly proportional to drug concentration. The elimination rate constant (Kel) represents the fraction of the drug in the body eliminated per unit of time)  A constant amount of drug is eliminated per unit time irrespective of drug concentration. **Elimination Parameters** Active proximal tubule transport of drugs from the interstitial space to the tubule lumen (urine).   **Organic Anion Transporters:** These mediate the exchange of organic anions and alpha-ketoglurate between the proximal tubule cells and the lumen or interstitial space. For example. OAT1 and OAT3 facilitate the uptake of organic anions form the blood into the tubule cell. Organic anions include various drugs that are cleared by the kidneys   **Organic Cation Transporters:** This transporter moves organic cations from the blood into the proximal tubule cell. Organic cations include various positively charged drug compounds **Elimination Half-life** Time taken for Plasma Concentration of a drug to decrease by half   Half-life allows us to make decisions related to: - Duration of action after a single dose. The longer the half life, the longer the plasma concentration remains in the therapeutic range - Dosing frequency - Time required to reach plasma steady state - Half life is directly proportional to the volume of distribution and inversely proportional to the total clearance   **Clearance** - Clearance is the volume of plasma that is cleared completely of the drug per unit of time (L/h) - CL tot = Rate of Elimination (µg/min)/Plasma Concentration (µg/mL) - Total drug clearance determines maintenance dose and rate of administration - For most drugs the rate of elimination is directly proportional to the drug concentration   **Steady State Plasma Concentration** At Steady-state, the rate of input to the body is equal to the rate of elimination - Steady state is usually achieved after 3 to 5 half lives with repeated dosing or sustained release of a drug - Css = Rate of drug elimination/CLtot - For **oral:** Css = F X Dose / CLtot X dosing interval   **First-Order Elimination Kinetics (Most Drugs)** - Rate of elimination is directly proportional to drug concentration - CL remains constant - A constant fraction of drug is eliminated per unit of time - Elimination rate constant (Kel) represents the fraction of drug in the body eliminated per unit of time - Kel = 0.693/Half life - Kel = CLtot/Vd   A Kel of 0.4s means that 40% of the drug is eliminated in one second   **Zero-Order Kinetics** - A constant amount of drug is eliminated per unit time irrespective of drug concentration - **Enzymes and Transporters** can get saturated - Clearance decreases with increase in concentration - Examples: Alcohol and Phenytoin   **Week Four** In pharmacodynamics, we study the molecular mechanism by which the association of a drug molecule with its target leads to a physiological response. To better understand how drugs work, we need to know their targets. Most drug targets are proteins, however there are a few exceptions. There are four main protein types: 1. Receptor -- binds to a drug and the drug can have an agonistic or antagonistic affect. Agonistic affect leads to ion channels opening and closing, enzyme activation/inhibition and DNA transcription. Antagonists have no effect, and the endogenous mediators are blocked 2. Ion Channels -- blockers block permeation channels and modulators can increase or decrease opening probability 3. Enzymes -- inhibitors inhibit a reaction and reduce its product; false substrates result in an abnormal metabolite produces 4. Transporters -- Normal transporters, inhibitors of transporters and false substrate transporters No drug acts with complete specificity. For example, adrenaline binds to a specific binding site on the adrenergic receptor. Most drugs show selectivity: preference for a molecular target at particular cells and tissues. Non-selective drugs act on one or more targets at therapeutic concentration Drug selectivity is dose-dependent. Drug specificity is not dose-dependent. Affinity is the tendency of a drug to bind to the receptor. It is measured by the dissociation constant (KD). At equilibrium:  Y axis is percentage of receptors occupied X axis is concentration of drug KD is the drug concentration at which 50% of the receptors are occupied Agonists = drugs that occupy receptors and activate them Antagonists = drugs that occupy receptors but do not active them. Antagonists block receptor activation by agonists  Efficacy: the capacity of a drug to activate a receptor and generate a response Potency: mixed function of both affinity and efficacy For most drugs, binding and activation are reversible processes Emax = maximal response a drug can produce EC50 -- concentration to produce a 50% maximal response. In general, the lower the potency the higher the dose needed  **Reduced Efficacy** reduces a drugs **Emax** **Reduced Potency** reduces a drugs **EC50** \*Dose response curve and concentration response curve are not the same L\> a response could be anything measurable inside of a cell Competitive antagonists are excellent drugs to decrease the effect of endogenous mediators or drugs. Reversibility binds to the receptors, at the same site as the agonist Important characteristics of competitive antagonists: - Shift the curve to the right without affecting the slope or Emax - Binding studies confirm competition Response of full agonist + partial agonist  An irreversible antagonist dissociates very slowly or not at all. The drug forms covalent bonds with the receptor. It shifts the curve to the right and effects the slope and Emax - A serial dilution is the stepwise dilution of a substance in a solution.  Usually the dilution factor at each step is constant.  For example, a 10 fold dilution series may contain solutions of 100, 10, 1 and 0.1 mM solutions. - You can make a serial dilution of a drug to determine inhibitory concentrations and plot a concentration-response curve. **Week Five**    **Enzymes** Enzymes are biological catalysts. They are very powerful and **very** specific Each enzyme catalyses a particular chemical reaction, **leaving the enzyme unchanged**.   A set of reactions by enzymes is called a **metabolic pathway.**   - Anabolic reaction \--\> synthesis - Catabolic reaction \--\> breakdown - Enzymes suffix -ase   **Cycle of Acetylcholine**   The synthesis of acetylcholine (an important neurotransmitter in the body) is done by the enzyme **choline acetyltransferase**. Acetylcholine is then packaged up to leave the axon. Once packed into a vesicle, acetylcholine leaves the neuron and begins to cross the synapse. It then reaches the other side of th esynapse and binds to the receptor causing the message to be sent. After the message is sent, Acetylcholine is released back into the synapse. Finally, the enzyme **acetylcholinesterase** breaks down acetylcholine, inactivating it.   In a clinical setting, if someone has a condition that causes muscle weakness (e.g., Myasthenia Gravis), an acetylcholinesterase inhibitor can be used to treat the condition as it will inhibit the ability of acetylcholinesterase to break down acetylcholine, leading to increased effect of acetylcholine as a neurotransmitter. Examples include **donepezil, pyridostigmine** and **rivastigmine.** These are reversible inhibitors   **Irreversible Inhibition of acetylcholinesterase enzymes** - Chemical warfare agents (e.g. sarin gas) - Insecticides (e.g., parathion) **False substrates** If a false substrate attaches to an enzyme, it results in an abnormal product. The false substrate competes for the binding site disrupting the normal metabolic pathway.   **Receptors** Receptors are protein molecules that when activated by transmitters/hormones/drugs mediate a biological effect. They are important for chemical signalling between/within cells   In pharmacology, a ligand is **any substance that binds to a receptor forming a complex.** They don't necessarily need to activate the receptor as an antagonist is also a ligand.   Endogenous ligands are substances made by our body, for example: - Hormones: Adrenaline is a endogenous ligand as well as a drug (the receptors are adrenergic receptors) - Neurotransmitters: GABA is an endogenous ligand (the receptors are GABA A and GABA B) - Growth Factors: Tumour Necrosis Factor (TNF) is an endogenous ligand (the receptors are TNFR1 and TNFR2)   **Intracellular Signalling Cascade** A ligand (first messenger) binds to the GPCR that will signal through the G proteins (the transducers) which will then activate effectors (for example, enzymes and ion channels). Effectors are responsible for the change in the second messenger levels (For example, calcium and cAMP). This signalling cascade will lead to physiological changes at the cellular level.   **Receptor Superfamilies** +-----------------+-----------------+-----------------+-----------------+ | Ligand-gated | G | Kinase-linked | Nuclear | | ion channels | protein-coupled | receptors | Receptors | | (Ionotropic | receptors | | | | receptors) | (metabotropic) | | | | | | | | | | (seven-transmem | | | | | brane | | | | | receptor) | | | +=================+=================+=================+=================+ | Ions |  | | | effects Other | | | | | ](media/image24 |   | | | |.png) | | | | | | | | | |   | | | +-----------------+-----------------+-----------------+-----------------+ | Also known as | Also known as | Agonist: | Ligand-activate | | ionotropic | metabotropic | protein | d | | receptors | receptors or | mediators | transcription | | | 7-transmembrane | | factors. | |   | receptors. This |   | | | | means it | |   | | Located in the | crosses the | Located in the | | | cell membrane, | membrane | cell membrane, | These receptors | | however, some | **seven | however, some | regulate gene | | are also | times.** | are also | transcription. | | present in | | intracellular | | | intracellular |   | |   | | membranes such | |   | | | as endoplasmic | Around 30-40% | | Located in the | | reticulum | of medication | Large | cytoplasm | | membranes. | available in | extracellular | (class one) or | | | clinics affect | ligand-binding | in the nucleus | |   | G-protein | domain linked | (class two). | | | coupled | to an | | | Oligomeric | receptor | intracellular |   | | assembly of | | domain by a | | | mostly 4-5 |   | single | After ligand | | subunits | | transmembrane | binding, they | | surrounding a | Located on the | helix. | form homodimers | | central | cell membrane. | | or heterodimers | | chloride pore. | |   | and translocate | | |   | | to the nucleus | |   | | Dimerization | where they can | | | Monomeric or | occurs when | transactivate | | Typically 2 | oligomeric | receptor is | or transrepress | | alpha, one | assembly of | activated. | genes. | | beta, one gamma | subunits | | | | and one delta | comprising of |   |   | | | seven | | | |   | transmembrane | Most cases the | The complex | | | alpha helices | intracellular | receptor+ligand | | Controls the | with | domain is | binds to | | fastest | intracellular G | enzymatic | hormone | | synaptic events | protein-couplin | having a direct | response | | in the nervous | g | effect. | elements in | | system. | domain. | | gene promoters | | | |   | and recruiting | |   |   | | co=activator or | | | | Activation of | co-repressor | | Effector is the | Not as fast as | these receptors | factors | | ion channel | ion channels | alter cell | | | | but faster than | transcription. |   | |   | receptors that | | | | | cellular |   | This receptor | | Examples | effects depend | | is located | | include GABAa, | on gene | Have | entirely inside | | Nicotinic ACH | transcription. | extracellular | the cell, | | and NMDA | | binding sites | therefore the | | receptors |   | where ligand | ligand has to | | | | can attach and | first cross the | |   | Effectors are | stimulate | bilipid | | | **channels or | enzymatic | membrane before | | GABAa is | enzymes** which | activity in the | it can bind to | | orthosteric | are activated | cell. | the receptor. | | site. | via G proteins | | | | | or arrestins. |   |   | |   | | | | | |   | Most | Then the | | Benzodiazepines | | kinase-linked | activated | | is allosteric | G proteins are | receptors are | ligand receptor | | sites. | **transducers.* | of | complex can | | | * | tyrosine-kinase | move into the | |   | | type, meaning | nucleus of the | | |   | they display | cell where it | | GABAa is the | | kinase activity | binds to DNA | | main inhibitory | Composed of | and that there | and regulated | | neurotransmitte | three subunits | is an amino | gene | | r | | acid Tyrosine | expression, | | | In its inactive | involved in | ultimately | |   | form, the alpha | that activity. | leading to | | | subunit has GDP | | synthesis of | | Glutamate is | attached to it. |   | specific | | the main | | | proteins | | excitatory |   | When ligand | | | neurotransmitte | | binds to two of | | | r | When the ligand | these | | | | binds to the | receptors, it | | | | receptor, the | causes | | | | affinity for | conformation | | | | GTP increases, | change that | | | | so GTP replaces | results in | | | | GDP. | aggregation of | | | | | both receptors. | | | |   | | | | | |   | | | | This in turn | | | | | causes the | One the dimer | | | | alpha subunit | is formed, the | | | | to dissociate | tyrosine | | | | from the | regions get | | | | beta-gamma | activated, | | | | complex, and | causing ATP to | | | | these complexes | become ADP, | | | | go to interact | which results | | | | with other | in outer | | | | enzymes and | phosphorylation | | | | proteins. | of the | | | | | receptors. | | | |   | | | | | |   | | | | This leads to | | | | | the beta-gamma | Once each | | | | complex being | tyrosine picks | | | | able to | up a phosphate | | | | activate a | group, | | | | target. Also, | different | | | | the alpha | inactive | | | | subunit bound | intracellular | | | | to GTP will | proteins attach | | | | activate target | themselves to | | | | one usually an | phosphorylated | | | | ion channel | tyrosine. This | | | | (e.g., calcium | results in | | | | or potassium | conformational | | | | channels). | change in the | | | | These are main | attached | | | | effectors for | protein, | | | | ßy units. | leading to a | | | | | cascade of | | | |   | activation that | | | | | produces | | | | After a short | cellular | | | | period, it will | response | | | | cause the | | | | | breakdown of | | | | | GTP | | | | | (hydrolysed) | | | | | into GDP + a | | | | | phosphate. | | | | | | | | | |   | | | | | | | | | | At that point | | | | | its stops | | | | | activating its | | | | | target and goes | | | | | back to resting | | | | | state. | | | | | | | | | |   | | | | | | | | | | There are three | | | | | types of G | | | | | protein that | | | | | are important | | | | | to remember: | | | | | | | | | | - Gs | | | | | | | | | | - Gi | | | | | | | | | | - Gq | | | | | | | | | |   | | | | | | | | | | Gs is a | | | | | stimulated G | | | | | protein that | | | | | activates an | | | | | enzyme called | | | | | Adenylyl | | | | | Cyclase. | | | | | Adenylyl | | | | | cyclase | | | | | produces cyclic | | | | | amp (cAMP) from | | | | | ATP. cAMP is an | | | | | important | | | | | second | | | | | messenger. cAMP | | | | | is the main | | | | | effector for | | | | | Gas and Gai | | | | | (Gas = | | | | | stimulation, | | | | | Gai = | | | | | inhibitory) | | | | | | | | | |   | | | | | | | | | | Gi is an | | | | | inhibitory G | | | | | protein that | | | | | inhibits | | | | | Adenylyl | | | | | Cyclase, thus | | | | | lowering the | | | | | levels of cAMP | | | | | in the cell | | | | | | | | | |   | | | | | | | | | | Gq is a G | | | | | protein which | | | | | activates a | | | | | class of | | | | | enzymes called | | | | | phospholipase C | | | | | (PLC). PLC | | | | | produces two | | | | | second | | | | | messengers, | | | | | diacylglycerol | | | | | (DAG) and | | | | | inositol | | | | | triphosphate | | | | | (IP3). These | | | | | are the main | | | | | effector for | | | | | Gaq. | | | | | | | | | |   | | | | | | | | | | DAG leads to | | | | | different | | | | | responses due | | | | | to activation | | | | | of protein | | | | | kinases C, | | | | | whereas IP3 | | | | | mediates | | | | | intracellular | | | | | release of | | | | | calcium | | | | | (increase in | | | | | calcium | | | | | increases | | | | | vesicle | | | | | release) | | | +-----------------+-----------------+-----------------+-----------------+   **Milliseconds Seconds Hours Hours** **FASTEST \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\> SLOWEST**   **Ligand-gated ion channels** - Also known as ionotropic receptors - Located in the cell membrane, however, some are also present in intracellular membranes such as endoplasmic reticulum membranes. - Oligomeric assembly of mostly 4-5 subunits surrounding a central pore - Controls the fastest synaptic events in the nervous system - Effector is the ion channel - Examples include GABAa, Nicotinic ACH and NMDA receptors     **G protein-coupled receptor** - Also known as metabotropic receptors or 7-transmembrane receptors - Located on the cell membrane - Monomeric or oligomeric assembly of subunits comprising of seven transmembrane alpha helices with intracellular G protein-coupling domain - Not as fast as ion channels but faster than receptors that cellular effects depend on gene transcription - Effectors are channels or enzymes which are activated via G proteins or arrestins - Adenylyl cyclase, the enzyme responsible for the production of cAMP - main effector for for Gas and Gai - Phospholipase C, the enzyme responsible for inositol triphosphate (IP3\_ and diacylglycerol (DAG\_ formation - effectors for Gaq - Ion channels are the main effectors bye ßy subunits      **Example** Opioid analgesics act by binding to mu-opioid receptors which is a GPCR coupled to inhibitory G proteins.   **Kinase-linked and related receptors** - Agonist: protein mediators - Located in the cell membrane, however, some are also intracellular - Large extracellular ligand-binding domain linked to an intracellular domain by a single transmembrane helix. Dimerization occurs when receptor is activated. - Most cases the intracellular domain is enzymatic having a direct effect. - Activation of these receptors alter cell transcription (slower effect) - However, they can also lead to faster responses. For example, insulin leads to change to gene transcription but also the phosphorylation activated by insulin causes the glucose transported to be translocated to the membrane. This is important for glucose to enter the cells.   **Example** Insulin binds to its receptor on the surface of its target cells. Insulin receptor is a tyrosine kinase-linked receptor   **Nuclear Receptors** - Ligand-activated transcription factors - These receptors regulate gene transcription - Located in the cytoplasm (class one) or in the nucleus (class two). - After ligand binding, they form homodimers or heterodimers and translocate to the nucleus where they can transactivate or transrepress genes. - The complex receptor+ligand binds to hormone response elements in gene promoters and recruiting co=activator or co-repressor factors   **Example** Glucocorticoids (e.g., hydrocortisone) bind to intracellular glucocorticoid receptor and translocate to the nucleus where it controls gene expression   A screenshot of a text box Description automatically generated **Receptors from all 4 superfamilies can be allosteric modulated**   **Functional Selectivity**   Refers to the ability of different ligands to selectively activate distinct signalling pathways through the same receptor. A single ligand can activate some signalling pathways while inhibiting others through the same receptor. For example, at the serotonin receptor, serotonin can selectively activate certain pathways while not affecting others.      **Transporters** - Also known as carriers - Important for the transport of molecules that are insufficiently lipid-soluble to penetrate lipid membranes on their own. - Transport ions and many organic molecules across the renal tube, the intestinal epithelium and the blood-brain barrier - The rate-limiting step is defined as the **slowest step** out of all that occur for a given metabolic pathway/chemical reaction.   Passive transport (downhill transport) Electrocfwnical High gradient Of eve Passive Faciitated Active transport (uphill transport) Electr\#fwnical gnEntiaI High gradient Of eve Syrnport Secondary active transport Antiport Primary active   **Types of Transporters**   **ATP binding cassette (ABC) transporters:** use energy from ATP hydrolysis to transport a wide range of substrates, including lipids, sterols, ions, small molecules, drugs and large polypeptides. Examples include P-glycoprotein (involved in multidrug resistance) and CFTR (cystic fibrosis transmembrane conductance regulator)   **Solute Carrier Family:** includes a diverse group of transporters that facilitate the movement of a variety of solutes, such as ions, amino acids, sugars and drugs, often using secondary activae transport of facilitated diffusion. Examples include SERT (serotonin transporter), DAT (dopamine transporter) and GLUT (glucose transporters).   **Transporter inhibitors** Many drugs act in the CNS affecting transport proteins. Examples are: - Antidepressants: - Psychomotor stimulants: **Selective Serotonin Reuptake Inhibitors** SSRIs block the serotonin transporter, preventing the reuptake of serotonin into presynaptic neurons. This increases serotonin levels in the synaptic cleft, improving mood and alleviating symptoms of depression. Examples include fluoxetine and sertraline.   **Dopamine Transporter Inhibitors** These inhibitors block the dopamine transporter, increasing dopamine levels in the synaptic cleft. This enhances dopaminergic signalling, which can lead to increased alertness and euphoria.  **Week Six** Ions are charged molecules made up of an unequal amount of negative electrons and positive proteins.   Sodium Potassium and Calcium are similar sixes and charges yet they are all selective for they respective channels. This is because channels are proteins made up of amino acids that carry charge too.   Different ion channels have different selectivity filters   **Factors of Ion Selectivity** 1. Size and charge: Ions have pores that are sized to fit specific ions. The charge of the ion and the electrostatic environment within the channel also play a role. Channels often have charged amino acids at the entrance of within the pore that attract or repel specific ions 2. Selectivity Filter: a narrow region of the pore that precisely coordinated specific ions. This filter is lined with amino acids that interact with the ion in a way that mimics the ion\'s hydration shell.   DEKA E=Glu, K=LYS G=Gly   Also, when potassium goes through a pore it gets dehydrated, whereas sodium and calcium stay partially hydrated.   Ions move toward electrochemical equilibrium and are driven by electricity and diffusion.   **Electricity** - electrical gradient will determine where the ion will flow based on the difference in charge across a membrane.   **Diffusion** - chemical (osmotic) gradient will determine where the ion will flow based on the difference in concentration of salts inside and outside the cell.   If you introduce an electrical field, Ions will move across the membrane. Ions carry charge and like magnets, positive sodium will move towards negative terminal (inside the cell) and likewise, negative chlorine will move towards positive terminal (outside cell).   Ions will move across the membrane passively provided channels are present and there is a concentration gradient i.e., more salt outside than inside or vice versa.   **Important -** since ions are charged they can\'t cross membranes via passive diffusion but they can move via ion channels (facilitated transport) and transporters.   Movement of ions through membrane can be: - Active - Passive - Done via transporters   +-----------------------------------+-----------------------------------+ | Ion Channels | Transporters | +===================================+===================================+ | Ion channels have a pore that | Transporters are involed in the | | once open allows ions to flow in | transport of ions against the | | or out of the cell based on | gradient using ATP. They do this | | electrochemical or osmotic | by changing shape. | | gradient. | | | | | |   | | | | | |   | | +-----------------------------------+-----------------------------------+ | Ion channels only transport ions | Transporters can also transport | | | small organic molecules such as | | | glucose, neurotransmitters and | | | drugs. | +-----------------------------------+-----------------------------------+ | Can only carry one type of ion | Transporters can carry two or | | | more ions/molecules to the same | | | direction (symport transport) or | | | opposite direction (antiport | | | transport) | +-----------------------------------+-----------------------------------+   **Important -** Some channels aren\'t as selective. For example, ligand-gated ion channels such as acetylcholine receptors can conduct potassium, sodium or calcium depending on the location.   **Voltage gated ion channel** is a common type of ion channel that is activated by the change in membrane potential - due to difference in charges inside and outside the cell membrane. Membranes have a resting membrane potential. Once ions are allowed in our out of the cell, this potential changes leading to change in voltage therefore opening or closing voltage-gated ion channels.   Other ion channels such as the potassium channels called G-protein couple receptors inwardly-rectifying potassium channels (GIRK channels) are activated by the beta-gamma subunits of G proteins.   The rapid movement of ions across the cell membrane causes action potentials to propagate from the cell body, down axons to the synapse where they initiate the release of neurotransmitters. Action potentials are the units of electrical information that connect neural circuits.   **Movement of Ions creating Action Potential** 1. Resting membrane potential: neurons have a resting membrane potential of about -70mV, maintained by the sodium-potassium pump, which actively transports sodium ions out of the cell and potassium ions into the cell. 2. Depolarisation: When a neuron receives a stimulus, voltage gated sodium channels open, allowing sodium ions to rush into the cell. This influx of positive ions causes the membrane potential to become less negative (depolarise). If the membrane potential reaches a threshold (around -55mV) and action potential is triggered. 3. Rising phase: During this phase, more sodium channels open, and sodium continues to flow into the cell, causing the membrane potential to become positive (up to +30mV) 4. Peak and repolarisation: at the peak of action potential, sodium channels close, and voltage-gated potassium channels open. Potassium ions flow out of the cell, causing the membrane potential to become negative again (repolarise) 5. Hyperpolarisation: sometimes, the outflow of sodium ions causes the membrane potential to become more negative than the resting potential 6. Return to resting potential: the sodium-potassium pump and other ion channels restore the resting pump and other ion channels restore the resting membrane potential.    Pain from injury leads to lots of very hyper-excitable Ion channels including sodium, potassium and T-type calcium channels.   Channelopathies may be caused by genetic factors or environmental factors. - Genetic factors - mutations that lead to malfunction of ion channels can cause multiple diseases such as epilepsy - Environmental factors - continuous exposure to pain or certain drugs may cause channels to malfunction leading, for example, to chronic pain   Examples: - **Cystic Fibrosis -** Caused by mutations in the CFTR chloride channel, leading to thick mucus build up in the lungs and digestive tract - **Long QT Syndrome** - Affects potassium or sodium channels in the heart, causing irregular heartbeats and increasing the risk of sudden cardiac arrest.     Ionic movement through cell membranes is effected by changes in the open/closed state as well as speed of open/closed state of channel. Correcting abnormal channel activity that causes disease states is a multi-billion dollar a year industry.   **Drugs that control Ionic movement** 1. Ion channel blockers e.g., tetrodotoxin 2. Ion channel openers e.g., diazoxide    In 2018, adverse effects of drugs, medications and biological substances were the second most common adverse event reported in hospitals (32%)   Approximately 2-3% of hospitals admission are estimated to be medicine-related causing significant morbidity and mortality. 1.4% are likely due to ADR on admission. This is estimated to increase two 3% if considering ADR on admission and during stay. - More than half of ADR-related admissions are considered preventable.   **Therapeutic Index** Used to compare the therapeutic effective dose to the toxic dose of a pharmaceutical agent.   **ED50 =** drug dose that produces a **therapeutic** response in 50% of the population **TD50 =** drug does that produces a **toxic** response in 50% of the population   The therapeutic index is TD50 divided by the ED50   Therapeutic effect Therapeutic Toxic effect 50% ED50 index TD50     **Therapeutic Window** The range of steady state concentrations of drug that provides therapeutic efficacy with minimal toxicity.   Therapeutic window does not guarantee safety and efficacy, however it indicates at which doses the probability of efficacy is high and of adverse effects is low.   Important to note - Therapeutic window is mostly determined by plasma concentration of the drug vs response in the population, while Therapeutic Index tends to plot dose vs response in the population   **Adverse drug reactions -** Harmful or unwanted effects of drugs      **Predictable (Type A) vs Unpredictable (Type B)** Predictable Unpredictable ---------------------------------------------------------------------------- ----------------------------------------------------------- Consequence of the main pharmacological effect of the drug or its known PK Unrelated to the known pharmacological action of the drug Common, especially for drugs with low therapeutic index Less common Mostly preventable and reversible More serious, requires drug withdrawal Dose related (too much or altered PK) Not dose related 0 may occur in very low doses   Idiosyncratic (unique to an individual)   **Classification of ADRs** +-----------------------------------+-----------------------------------+ | Type of ADR | Examples | +===================================+===================================+ | Dose-related (augmented) | Toxic effects: digoxin, SSRIs | | | | | | Side effects: Anticholinergic | | | effects of TCAs | +-----------------------------------+-----------------------------------+ | Non-dose related (bizarre) | Immunological reactions: | | | Penicillin hypersensitivity | | | | | | Idiosyncratic reactions: | | | Malignant hyperthermia | +-----------------------------------+-----------------------------------+ | Dose-related and time-related | Hypothalamic-pituitary-adrenal | | | axis suppression by | | | glucocorticoids | +-----------------------------------+-----------------------------------+ | Time-related | Teratogenesis (thalidomide, | | | valproate) | | | | | | Carcinogenesis | +-----------------------------------+-----------------------------------+ | Withdrawal | Opiate withdrawal syndrome | | | | | | Myocardial ischemia (beta | | | blocker) | +-----------------------------------+-----------------------------------+ | Unexpected failure of therapy | Inadequate dosage of oral | | | contraceptive, particularly when | | | used with enzyme inducers | +-----------------------------------+-----------------------------------+   **Predisposition to ADRS** **Patient Related:** - Age - Gender - Underlying Disease - Hepatic and Renal function - Body weigh and fat distribution - Genetic Factors **Drug Related:** - Other drugs taken - Smoking or alcohol intake - Polypharmacy - Route of administration - Dose of the drug and frequency   Genetic/Hereditary factors: certain hereditary factors may inhibit your bodys ability to produce enzymes that are responsible for metabolising drugs, e.g., a genetic variation where your body cannot produce appropriate levels of certain CYP enzymes that are important for stage one metabolism. In this case the concentration of the drug may shift from therapeutic range.   Pre-exisitng diseases: people with pre-existing diseases particularly liver and kidney disorders can increase predisposition to ADRS as these organs are the main organs involved in drug metabolism and excretion. dysfunction of these organs can decrease the body\'s ability to metabolise and excrete drugs efficiently and effectively which can cause the drug to accumulate leading to drug toxicity which increases risk of drug toxicity and adverse drug reactions.   **Drug Interactions** - Drug-Drug interactions - Drug-Food interactions - Drug-Supplement interactions - Drug-Medical Condition interactions   Drug-Drug interactions are involved in 10-20% of ADRs and are especially common in the elderly   Types of drug-drug interactions - Behavioural (altered compliance) - Pharmacokinetic (altered concentration) - Pharmaceutic (outside the body) - Pharmacodynamic (altered effect) **Pharmacodynamic interactions** are the most common. - Drugs with similar actions produce additive effect e.g., Alcohol and benzodiazepines (both are CNS depressants) - Drugs that have opposite effects may cancel each others effects e.g. beta blockers and beta agonists   **Pharmacokinetic interactions** - Altered bioavailability e.g., oral contraception and antibiotics - Altered distribution e.g., displacement of drug bound to plasma albumin - Altered clearance e.g., metabolism, prodrugs, excretion   A screenshot of a computer Description automatically generated   **Poisoning** Exposure to pharmaceuticals, illicit drugs or chemicals leading to damaging physiological effects.      **Week Seven** **Factors affecting individual drug response** - Age - Disease state - Gender - Weight - Diet - Drug interaction - Environment - Genetic factors   **Mutations and Polymorphisms** - Mutations occur in less than 1% of the population - A polymorphism is a DNA sequence variation that is common in the population (\>1%)   **Single Nucleotide Polymorphisms** - A SNP is a DNA sequence variation that occurs when a single nucleotide in the genome sequence is altered - Typically one of the alleles will be the predominant allele, being found in the majority of the population, while the other allele will represent the minor variant - SNPs can be classified as: \*A protein that has the sequence that is found in majority of the population is called the wild-type protein. page7image629840928   **Pharmacogenomics** - The term pharmacogenomics is the study of how an individuals genetic inheritance affects the body\'s response to drugs - Goals of pharmacogenomics: **Pharmacogenetic** is a subset of pharmacogenomics. It is the study of how inherited variation affects drug response and metabolism. It is often a study of variations in a targeted gene, or group of functionally related genes.   A pharmacogenetic factor is any genetic factor that influence drug response/toxicity. For example, a mutation in a gene important for any stages of drug disposition (ADME) or a mutation in the drug target. It is important to highlight the gene, what does it encode (e.g., CYP2D6) and how this mutation affect the pharmacology of the drug being discussed.    **A118G at µ-Opioid Receptor genetic variation** - Most commonly occurring (ranging 40-50%) - Arises from an A to G substitution at nucleotide 118, resulting in an asparagine to aspartic acid amino acid exchange in the N-terminal domain of µ-opioid - The A118G SNP has been implicated in a wide variety of disorders, such as drug addiction and stress responsivity, and in treatment responses, including dependence and pain reduction. Although the evidence is conflicting.   **Enzyme as a Target** - Vitamin K epoxide reductase is an example of an enzyme with genetic contributions to variation in drug response. - Warfarin inhibits VKOR and thereby, reduce the synthesis of active clotting factors. - Encoded by VKORC1-mutation in this gene causes warfarin resistance. - Carriers of this mutation require exceptionally high warfarin dose to achieve effective anticoagulation   **Homozygous** - Both alleles encode for identical protein **Heterozygous** - Different alleles (e.g.; it can be one functional and one non-functional enzyme) CYP enzymes are known to be a challenge in pharmacology because not only they have many variations (SNPs) but also they have copy-number variation. This means while some people may have none (yes, not express at all; genes are deleted), other may have 10 alleles or more. Imagine all the possible combinations\... it is a pharmacological nightmare. This can greatly impacted expected therapeutic effect, toxicity, etc.    **Pharmacogenetic Test** - Amplichip CYP450- FDA approved kit - Test assays DNA purified from human blood to genotype two important CYP subtypes - The assay detects up to 33 CYP2D6 and 2 CYP2C19 alleles.   In Australia, there are Medicare rebated tests for: - Abacavir (HIV) - HLA-B\*5701 variant \--\> severe/deadly hypersensitivity in 5% - Azathioprine (immunosuppression) - thiopurine methyl transferase \--\> 1-5% bone marrow suppression Biological drugs contain an active substance derived from or extracted from a biological system. They are often administered as an injection or infusion.   Biological drugs includes proteins, antibodies and oligonucleotides used as drugs. There are first-generation and second-generation biologicals   **First-generation** Purified extracts used to be the only option for treating protein hormone deficiency. Now we can obtain such products using genetic engineering techniques (recombinant plasmids)   **What is a protein expression system?** Refer to the type of living organism that is used to grow the desired protein. Most common systems for biopharmaceuticals are bacteria, yeast and mammalian cells.   **Second-generation (Engineered protein)** We can alter the protein prior to expression in many ways. This is beneficial for multiple reasons such as the modification of pharmacokinetic properties, creation of novel fusion or other proteins and reducing immunogenicity.   **Monoclonal Antibodies (-Mab)** Antibodies are large proteins produced by activated B cells (plasma cells) which are important cells to our immune system. Each antibody binds to a specific antigen leading to an effect, for example: - Neutralisation - Agglutination - Precipitation Monoclonal antibodies are made by identical immune cells and they bind to the same epitope   **Antigen** is a molecule, usually part of a pathogen, that stimulates the immune system to produce antibody against it.   **Epitope** is a part of the antigen that binds to a specific antigen receptor on the surfaceof B cells.   Binding between the receptor and epitope occurs only if their structures are complementary.   **Pharmacokinetics** Biological drugs are very big molecules        **Can Biologicals be reproduced?** In contrast to most small molecule drugs that are easily chemically synthesised, most biologics are complex and are not easily characterised so they cannot be reproduced   **Gene therapy** The addition of genetic material to cells to prevent, alleviate or cure disease. Potential applications include: - Cure of diseases caused by a single defective gene (monogenic disease) such as cystic fibrosis and haemoglobinopathies - Improvement of conditions with or without a genetic component, including many malignant, neurodegenerative and infectious diseases   **Antisense oligonucleotides** Binds complementary to mRNA and blocks translation. Following parental administration, they are distribute widely throughout the body with the exception of the CNS. **Week Eight** The first documented treatment is traced back to approximately 3000BC. Many drugs were extracts of natural plants. Some of those early drugs are still in use today but in improved forms. For example:   - Ephedra Vulgaris was noted to treat number of conditions e.g.. Cough. Its active component is ephedrine - Now, its diastereomer (Pseudoephedrine) is used in cold remedies.   This included isolation and synthesis of the active ingredients and derivatives of natural products. For example, the isolation of cocaine from coca leaves (1860) and synthesis of heroine from morphine (1974).   Some discoveries were simply due to serendipity e.g., 25 years after its synthesis, Humphry Davy inhaled nitrous oxide to see if it was harmless. This led to its discovery as inhalational anaesthetic.   ÅuxøtdUOO     **Stages of modern drug discovery and development** 1. Drug Discovery 2. Preclinical Development 3. Clinical Development (three phases) 4. Regulatory approval 5. Phase 5      **Modern Drug Discovery** - It takes about 10-15 years for a drug to first be used in human patients - The process takes about 2.7 billion USD - There are extensive regulatory requirements to bring a medicine from invention to pharmacy shelves - The process of drug development is challenging, time consuming, expensive and requires consideration of many aspect   **Rational Drug Design** Involves the systematic approach to using protein-structure techniques for the discovery of new drug ligands against drug targets, whose functionally roles in cellular processes and 3D structural information may be known or unknown   The first step is **target selection** - A target is a protein whose function can be modulated by a therapeutic agent to deliver a change in disease processes of sufficient efficacy to form the basis of a viable product - A target needs to be druggable   The next step is **target validation** - To improve disease linkage - To test the hypothesis for efficacy in disease - Decreases target attrition due to failure of hypothesis at later stages - Ensures attrition that does occur happens early - Increases confidence with increased investment in a target   The next step is **High-throughput screening (HTS)** - millions of compounds are screened at a single dose concentration against a specific target. This identifies **actives** - compounds that causes an affect. Once you confirm a compounds activity, you then construct a **concentration response curve** with the compound and the target to optimise the molecule.   **Structure bases drug design** - design of new drugs based on the knowledge of the structural characteristics of the target protein or nucleic acid   - Structural characteristics of target could be from x-ray crystallography, NMR or homology modelling - Virtual screening of compounds is conducted to predict actives   **Ligand based drug design** - used in the absence of the receptor 3D information - Relies on the knowledge of molecules that bind to the biological target of interest - Structure activity relationships and pharmacophore modelling are used   **Lead optimisation** - To identify suitable compounds for testing in a clinical setting - The molecular features will be modified to optimise potency against the enzyme target, cellular and toxicity assays - Improve on oral absorption, slow metabolic clearance in vivo - Display activity in an animal model of the disease - File intellectual property claims   Drug discovery starts with target selection 4. The target needs to be identified and va\.... To select a good target, it is important to understand the disease process including the cellular mechanisms of disease. L Hit identification e\' is completed by I\'ligh-throughput s\... (HTS). Using this essay millions of compounds from drug libraries can be tested against the target chosen. hit compound \" 4 is then optimised by changing their ead identification 4 -\>The chemical structure to produce the lead compound Lead optimisation 4 is the last stage of drug discovery where the lead compounds are optimised to present desirable characteristics such as better efficacy, potency, and harmacokinetics 4. New promising compounds can be   **Pre-clinical studies** - It is an essential and legal requirement to evaluate safety in at least 2 animal species before commencement of studies in humans - Animals are usually rats and dogs - Required to have functional activity in relevant safety species      **Clinical Development** - Often comprises 4 stages of overlapping phases of clinical trials - Clinical trials are specifically designed to intervene, and then evaluate some health-related outcome, with one or more of the following objectives - To diagnose or detect disease - To treat an existing disorder - To prevent disease or early death - To change behaviour, habits or other lifestyle factors   **Clinical Trials** A controlled clinical prospective research study that compares the effect, safety and value of new interventions against a control in human beings. A properly planned and executed clinical trial is a powerful experimental technique   In Australia, clinical trials are regulated by laws and codes of conduct and they must be approved by a *Human research ethics committee,* which checks that the research conforms to the requirements of the *National statement on ethical conduct in human research.*   Clinical trials must be reasonably safe to participants and have a favourable risk-benefit ratio.   **Principles of conducting clinical research** 1. Social and clinical value 2. Scientific validity 3. Fair subject selection 4. Favourable risk-benefit ratio 5. Independent review 6. Informed consent 7. Respect for potential and enrolled subjects   **Number of participants** - Phase I: 20-40 - Phase II: 30-100 - Phase II: \> 100 - Phase IV: \> 10,000   **Phase I** - Testing new drugs for the first time in humans - Healthy volunteers - Primary concern = safety, side effects, best dose and formulation method - Primary aim = Identify maximum tolerated dose (MTD), dose-limiting toxicities (DLTs) and the recommended phase II dose (RPTD) - Secondary aims = describe the toxicity profile of the new therapy in the schedule under evaluation, assess pharmacokinetics and assess pharmacodynamic effects - Pitfalls: Chronic toxicities usually cannot be assessed, cumulative toxicities usually cannot be identifies, uncommon toxicities will be missed   **Phase II** - At RPTD, the efficacy is tested and the toxicity profile is refined - Primary aim = screen out ineffective drugs, sending promising agents to phase II   **Phase III** - Randomised and controlled - Preferably double-blind\* - Relatively large - Primary aims: provide definitive answers on whether a new treatment is better than the control group or non-interventional standard care and monitor adverse effects and collect information that will allow the intervention to be used safely   \*Blinding at the stage of applying the intervention and measuring the outcome is essential if bias is to be avoided. The subject and investigator should ideally be blinded to the assignment. Blinding is achieved by making the intervention and the control appear similar in every respect.   **Phase IV** - After registration and marketing - Designed to monitor the effectiveness of the approved intervention in the general population - Collect information about any adverse effects associated with widespread use over longer periods of time - Investigate the potential use of the intervention in a different condition or in combination with other therapies - Relatively large number of participants - Used to continue to monitor efficacy and safety **Placebo Effect** - A placebo is a substance that appears to be a medical intervention but isn\'t one - Examples include sugar pills or saline infusions - Its estimated that 1 in 3 people experience the placebo effect - Placebo effect: any improvements in a symptom or physiological condition or reported side effects of a participant receiving a placebo treatment - Due to classical conditions - when you associate something with a specific response.   - The nocebo effect is based on negative expectations to the intervention. For example, if the participant is told that the tablet may cause headache and dizziness, the participant will feel the adverse effects even if allocated to the control arm.   **Vaccines approval** - The TGA rigorously assesses vaccines for safety, quality and efficacy before they can be used in Australia - Vaccines receive the same high level of scrutiny - TGA uses the best available scientific evidence to assess the risks and benefits of each vaccine - Evidence requirements are based on the international guidelines developed by the European Medicines Agency - TGA carefully assesses the results of clinical trials and the way in which the trials were conducted. - TGA requires well-designed trials of a sufficient length with a sufficient number of people who represent the people for whom the vaccine is intended - The results must demonstrate that the benefits of the vaccine greatly outweigh the risks - The TGA\'s decision for use in Australia is informed by the advice of the Advisory committee on vaccines - The TGA monitors vaccines for safety after they are supplied in Australia.   **Covid-19** - The bar for vaccine safety and efficacy is extremely high, recognizing that vaccines are given to people who are otherwise healthy and specifically free from the illness. - During global health emergencies, the WHO Emergency Use Listing Procedure (EUL) may be used to allow emergency use of the vaccine. - mRNA Vaccines are New, but Not Unknown. Researchers have been studying and working with mRNA vaccines for decades. - As soon as the necessary information about the virus that causes COVID-19 was available, scientists began to build the unique spike protein code into an mRNA vaccine. - Beyond vaccines, cancer research has used mRNA to trigger the immune system to target specific cancer cells. **Who is checking medicines?** The organisation that has responsibility for the import, supply, or export Of medicines in Australia is the Therapeutic Goods Administration The Therapeutic Goods Act 1989 requires that products must be entered on the Australian Reqister of Therapeutic Goods (ARTG) TO make this happen a sponsor (usually the company that will supply or manufacture the product) must submit an application and pay fees to the TGA This presentation will take you through some Of the critical things the TGA does   **What are Therapeutic Goods?** - Medicines = including prescription, OTCs and complementary medicines - Biologicals = something made from or containing human cells or tissues - Medical Devices = including instruments, implants and appliances   Also regulated other therapeutic goods such as tampons and disinfectants   **Regulated medicines include:** - Prescription medicines - Over-the-counter medicines - Complementary medicines - Vaccines - Blood, blood components and plasma derivatives   **Two broad categories of medicines**    - All prescription medicines are registered - Most OTCs are registered - Few complementary medicines are registered - Registered medicines have an \'AUST R\' on the label or packaging   **Registering a new medicine** - It takes approximately 11 months to evaluate one new higher risk prescription medicine   **Quality Data** - Composition of the substance and the product - Batch consistency - Stability data - Sterility data - Impurity content   **Safety and Efficacy Data** Nonclinical - evaluated by toxicologists and pharmaceutical chemists - Pharmacology data - investigating efficacy - Pharmacokinetic data - Toxicology data - investigating safety Clinical - evaluated by a medical doctor - Mostly results of clinical trials   **Role of TGA** - Assessing risks - Balance benefits with risks - Consider whether a medicine should be used in the proposed population for the proposed indication - Use PI as a risk management tool - Consider other risk management tools   **Product information document** - Document is approved by the TGA - The product is only authorised for specified patient population for specified indications - All other use is \'off-label\' and the benefit-risk profile has not been considered by the TGA - The precautions section gives details of some of the risk involved   **Medicine Scheduling - The Poisons Standard** - Scheduling is the legal process is used to restrict potentially dangerous drugs and chemicals to enable their safe and effective use - The higher the number of schedules, the more restricted is the access - Scheduling decisions are published on the TGA website - Only registered medicines are scheduled   Schedule classification Type of Medicine Example ------------------------- ------------------------------------------------------------------------------ ----------------------------------- Schedule 2 Pharmacy only medicine Large packet sizes of paracetamol Schedule 3 Pharmacist only medicine Proton Pump Inhibitors Schedule 4 Prescription only medicine Blood pressure medications Schedule 8 Controlled drug - additional restrictions on storage and supply of medicines Strong analgesics   **Listed Medicines** - Some OTCs - Most are complementary medicines - Must not contain substances that are schedules in the Poisons Standard - Must contain pre-approved ingredients   **Regulating Listed Medicines** - Only pre-approved low risk ingredients - Receive a lesser degree of checking - Regulation centres on the safety of ingredients and consistency of manufacturing process - Independent expert advice - Listing on the ARTG   **Conditions** - Does not claim or imply it will be useful in the treatment or prevention or serious illnesses   **Sterility** Dosage forms that must be supplied sterile include: - Injections - Ophthalmic use - Irrigation use - Intraurethral use - Used as an implant - Use on open wounds or burns - Otic use post surgery - Liquid inhalants intended for nebulisation - Peritoneal dialysis solutions   **Special Cases** Helps health professionals gain access to products that their patients need, which have not been approved for use in Australia - Clinical trial exemption and Clinical trial notification schemes = access unapproved medicines through participation in a clinical trial - Special Access Scheme = Import and/or supply an unapproved therapeutic good for a single patient for a case-by-case basic - Authorised prescribers = can prescribe a specified therapeutic good to a patient with a particular medical condition   **Advertising Medicines** - The labelling, packaging and description of what the medicine should be used for are all regulated by the TGA - Advertising of prescription medicines to consumers is illegal in Australia   **Active and excipient ingredients** - An active ingredient is a therapeutically active component - An excipient ingredient is an ingredient in a medicine\'s final formulation that is not a therapeutically active component e.g., preservatives, tablet coatings, ingredients that contribute to fragrance or flavour   **Generic Medicines must be bioequivalent** - Bioequivalence refers to whether the generic medicine releases the active ingredient into the bloodstream at the same rate and to the same extent as the original medicine - Blood samples are taken at different times and the rate and extent of absorption of the active ingredient into the blood is compared for the generic and original medicines   Generic and Brand Name drugs must have the same: - Active ingredients - Excipients - Strength/Concentration - Dosage form - Route of administration - Rates and extents of bioavailability of the active ingredient   **Biosimilars** A biosimilar is a biological medicine that is comparable in quality, safety and efficacy to the reference biological medicine   Therefore both the biosimilar and its reference medicine will have the following similar characteristics: - Physicochemical - Biological - Immunological - Efficacy and safety   **Pharmaceutical Benefit Scheme** - The PBS is an Australia Government program that benefits all Australians by making medicine more affordable - The PBS schedule lists all the medicines available to be dispensed to patients at a government-subsidies price - Not all medicines approved by the TGA are listed in the PBS schedule - Sometimes medicines are subsidised for one indication but not for others, or conditions applies (usually it is related to quality of evidence and cost) **Week Nine** **Smoking Ceremonies** - Used for welcoming, acknowledgements and healing   **Bush Medicines** **Red Bloodwood** - A medium sized Australian evergreen tree that grows to 15m. It is endemic to the coastal areas of NSW and Queensland. The leaves, resin and oil are used as a traditional Aboriginal herbal medicine. The essential oil is found in the leaves and is antiseptic astringent and parasiticide.   It can be used to help relieve coughs and colds, sore throats and other infections. A few drops of oil can be added to boiling water and inhaled as steam, or rubbed on the chest or throat. The dry resin and gum contains tannin and is powerfully astringent, it is used internally in the treatment of diarrhoea and bladder inflammation. The gum can be used to bind cuts to aid healing   The leaves can be burnt to help kill airborne bacteria. However, if red bloodwood oil is ingested in large doses, it can cause harm and even be fatal   **Emu -** Australia\'s tallest flightless bird, reaching between 1.6 and 1.9 m tall. Emus are primarily found in sclerophyll forests, open woodland and savannah woodland habitats across Australia. **Emu oil** is derived from the fat of this bird. The fat is high in omega-3, omega 6 and omega-9 fatty acids.   Traditionally, people ate emu meat, eggs and also used emu oil for conditions such as dry skin, wound healing and sore muscles. Nothing was wasted, the sinew, bone and feathers were all used.   Emus were once found in Tasmania, but were exterminated soon after Europeans arrived. Two dwarf species of emus that lived on Kangaroo Island and King island also became extinct. The colonial destruction of indigenous Australian cultures also parallels the destruction of indigenous plants, animals and ecosystems.   Today, emu oil and meat is nor commercially derived from birds farmed on emu farms. Contemporary uses of emu oil include ingestion of capsules \'Omega 3\' and applied to the skin as anti-inflammatory. It also has cosmetic applications such as moisturising skin and properties that resemble mineral oil.   **Bio-piracy: US companies patenting extract from Kakadu Plum** The Kakadu Plum is the highest known source of natural vitamin C on the planet. Known qualities: - High in vitamin C - Anti-inflammatory - High in antioxidants   Potential Qualities: - Anti-Alzheimer\'s/Dementia - Anti-Cancer - Anti-Diabetes **Week Ten** **[Anti-inflammatory Drugs]**   **Broad definition of inflammation -** \"Protective response of the organism to stimulation by invading pathogens or endogenous signals such as damaged cells, thus resulting in the elimination of the initial cause of injury, the clearance of necrotic cells and tissue repair.\"   **5 cardinals of inflammation:** 1. Heat 2. Redness 3. Swelling 4. Pain 5. Loss of function   **Prostaglandins** and **Leukotrienes** are key **pro-inflammatory mediators.**   Anti-inflammatories are divided into 5 major groups: 1. **Cyclo-oxygenase inhibitors (NSAIDs)** 2. **Glucocorticoids** 1. Antirheumatic drugs (DMARDs) 2. Cytokines modulators and other biological agents (bDMARDs) 3. Others that do not fit in the above groups (antihistamines and drugs to control gout   **Cyclo-oxygenase (COX) inhibitors** NSAIDs are among the most widely used of all agents. Some are available OTC, and are used to treat minor aches and pains.   Different NSAIDs are **chemically unrelated**. Despite this diversity all the NSAIDs possess analgesic, antipyretic and anti-inflammatory properties.   They share to varying degrees the same adverse reactions.   **NSAIDs Pharmacodynamics** The COX1 and COX2 Enzymes are homodimers.   The purpose of this enzyme is a transfer reaction that **converts arachidonic acid (substrate) into prostaglandins (product). This leads to platelet aggregation.**   Aspirin is slightly different to all other NSAIDs as its reaction results in **irreversible inhibition of the enzyme.** It is mainly used to decrease platelet aggregation in cardiovascular diseases.   **COX1 vs COX2** Because of the side pocket on COX2 enzyme, we were able to produce COX2 selective drugs, such as **Celecoxib.**      **Analgesic effect** Decreased production of prostaglandin \--\> less sensitisation of nociceptive nerve endings to inflammatory mediators such as bradykinin and 5-hydroxytryptamine   **Anti-inflammatory effect** Reduces vasodilation and , indirectly, oedema by decreasing prostaglandin E2 and prostacyclin synthesis   **Antipyretic effect** NSAIDs prevent the release of prostaglandins by interleukin-1 in the CNS, where prostaglandins elevate the hypothalamic set point for temperature control, therefore preventing fever.   Cardiovascular Risk Associated With NSAIDs and COX-2 Inhibitors -2 SELECTIVE COX-2 Selective NSAID ItEreased risk tor CV Decreased risk for Gl side ettects SEMISELECTIVE Meloxicam, didofenac, etodolac, indomethacin, piroxicam, nabumetone, sulindac Semiselective NSAIDs affinity COX-2 still retain activity COX-I Use w ith caution in at Erreased CV risk Ibuprofen, naproxen Nonselective NSAIDs Decreased risk tor CV events Increased risk for Gl side effects at   **Pharmacokinetics** - Route of administrations - topical, enteral and parenteral    - Site of absorption - stomach and small intestine (presence of food and antacids and delays absorption. - Distributions - highly bound to plasma protein. Wide spread including breast milk and cross placenta - Metabolism - Liver - Excretion - Kidneys Drug Aspirin (Solprin, Cartia) Celecoxib (Celebrex) Diclofenac (Voltaren) Ibuprofen (Nurofen) Meloxicam (Mobic) Naproxen (Naprosyn) Half-life (h) 0.25 (2-19) 4-15 1-2 2-2.5 20 12-15 N\# doses/day I or 2 2 or 3 3 or 4 Routes Oral Oral Oral, rectal, topical Oral, topical Oral Oral Comments Non-selective, analgesic and antiplatelet agent, OTC Selective COX-2 inhibitor Non-selective; OTC Non-selective; OTC Selective COX-2 inhibitor at low dosage Nonselective, OTC   **Corticosteroids** **Steroidal **means it is related to steroidal hormones and their effects. In our body steroidal hormones come from cholesterol (cholesterol is a type of steroid) and examples are: - Sex hormones- testosterone, oestradiol and progesterone - Glucocorticoids - cortisol - Mineralocorticoid - aldosterone Therefore, NSAIDs are unrelated to cholesterol molecule and do not have the same mechanism of action of steroidal anti-inflammatory drugs (the glucocorticoids).   Corticosteroids are synthesised from **cholesterol**. Their main effects are: - Resistance to stress - Metabolic effects - Anti-inflammatory - Immunosuppressant   Glucocorticoids are produces in the **zona fasciculata** are of the **adrenal glands.**   Control of corticosteroids release is done by hypothalamic and pituitary control through a negative feedback loop. Two rhythms appear to influence glucocorticoid release: - Circadian rhythm - Ultradian rhythm   **Corticosteroids as drugs** They are highly effective in controlling inflammation, but their use is largely limited by their adverse effects. They usually finish with the suffix **-one.**   Examples include: - Betamethasone - Dexamethasone - Prednisolone   **Mechanism of action** - Both NSAIDS and corticosteroids affect the arachidonic acid cascade, but in different ways. - Corticosteroids don't directly inhibit the enzyme phospholipase A2. Instead, they transactivate protein Annexin 1, which is an inhibitor of phospholipase A2, inhibiting the arachidonic cascade. - Corticosteroids bind to intercellular receptors that form a complex and translocates to the nucleus. In the nucleus, it modulated gene transcription. It can transactivate or transrepress. - It requires time to produce an effect   **Adverse effects**   **NSAIDS** **Corticosteroids** --------------------------------------- ----------------------------------------- Nausea, diarrhoea, headache Adrenal suppression Dyspepsia, GI ulceration and bleeding Dyspepsia Raised liver enzymes Hypokalaemia, hyperglycaemia Dizziness Myopathy, muscle weakness and wasting Salt and fluid retention Sodium and water retention, oedema Hypertension Hypertension   Fat redistribution   Skin atrophy, bruising, acne, hirsutism   Diabetes, osteoporosis, fractures **Contraindications** NSAIDS Corticosteroids --------------------------------------------------------------------- --------------------------- Hypersensitive reaction Hypersensitive reaction **Abnormal renal function** **Peptic ulcer** **History of peptic ulcer disease** **Osteoporosis** Chronic constipation **Diabetes** **Pregnancy** Systemic fungal infection **Cerebrovascular disease (especially selective COX-2 inhibitors)** Active Tuberculosis   **Paracetamol** It has analgesic and antipyretic properties. It has a very weak/**negligible** anti-inflammatory effects - not a suitable substitute for NSAIDs in chronic inflammatory conditions such as RA. However, it is well tolerated and low incidence of GI side effects.   **Autonomi