Pharmacology and Toxicology - Principles of Pharmacology I PDF

## Pharmacology and Toxicology - Principles of Pharmacology I ### Pharmacology - **Pharmacology** - Scientific study of the effects of drugs and chemicals on living organisms. - **Drug** - Natural or synthetic chemical substance that affects a biological system. ### Importance of Pharmacology -...

## Pharmacology and Toxicology - Principles of Pharmacology I ### Pharmacology - **Pharmacology** - Scientific study of the effects of drugs and chemicals on living organisms. - **Drug** - Natural or synthetic chemical substance that affects a biological system. ### Importance of Pharmacology - Understand the biochemical and physiologic aspects of drug effects. - Determine the effectiveness and safety of drugs. - Help in the diagnosis, prevention, and treatment of diseases. ### Toxicology - **Toxicology** - The field of science that studies the harmful and adverse effects of chemicals, substances, physical agents, or situations that have on living organisms and the environment. ### Mechanisms of Absorption of Drugs from the Gastrointestinal (GI) Tract - **Passive diffusion:** - Vast majority of drugs absorbed by this mechanism. - **Driving force:** Concentration gradient across a membrane separating two body compartments. - **Moving of drug:** From an area of high concentration to one of a lower concentration. - Passive diffusion does not involve a carrier. ### Four Main Pharmacokinetic Processes - Four main components of pharmacokinetics include: Absorption, distribution, metabolism, and excretion (ADME). - They are used for explaining the various characteristics of different drugs in the body. - The pharmacokinetic processes may be influenced by: - Patient factors such as the sex, age, genetics, and diseases. - The properties of drugs such as protein binding, molecule size, and chemical characteristics. ### Effect of a Drug Depends On - **Disease states:** - Chronic kidney diseases affect dramatically the drug pharmacology. - Pharmacokinetics studies how the body does to the drug. - **Number of receptors:** - Differentially expressing of receptors mediate biological responses of different levels. - **Drug dosage:** - Increasing drug amount increases the drug effect until saturation of the receptor. - **Drug potency/affinity:** - More potent drug - Faster binding to the receptor and slower releasing from the receptor. - **Drug efficacy:** - Ability of the drug to block or activate the receptor. ### What is the Ligand - Ligands can be anions, cations, or neutral molecules that bond to a central metal atom or ion. - It is a chemical messenger that binds to a protein, thus producing a chemical signal. - Ligand can be organic or inorganic molecules. - Ligand can also be natural or synthetically made in a laboratory. ### Drug-Receptor Interactions - Concern with the ability of a drug to affect a given receptor. - **Probability or strength of the drug to occupy a receptor at any given time** - **Drug's affinity**. - **Degree to which a drug or ligand activates the receptors and resulting in the cellular response** - **Intrinsic efficacy**. ### Bioavailability - It is the rate and extent that an administered drug reaches the systemic circulation. - Determining the bioavailability is important, especially for calculating the drug dosages for the nonintravenous routes of administration. - **Example:** 100 mg of a given drug is administered orally by a patient. 60 mg is absorbed unchanged. What is the bioavailability? - **Answer:** The bioavailability is 0.6 or 60%. ### Drug Distribution - Volume of Distribution **Features of Drugs Affecting the Volume of Distribution** - **Acid-Base Characteristics:** - Drugs may have a propensity to bind proteins throughout the body. - Reach a point of equilibrium between a bound & unbound phase. - **Basic (alkaline) molecules:** - Strong interactions with negatively charged phospholipid head groups located on phospholipid membranes. - Will leave the systemic circulation leading to higher Vd as compared to acidic molecules. - **Acidic molecules:** - Higher affinity for albumin molecules at lower lipophilicity than neutral or basic molecules. - More likely to bind albumin and remain in the plasma. - Leading to lower Vd as compared to more basic molecules. - **Lipophilicity:** - **Lipophilic molecules:** - More likely to pass through lipid bilayers. - More likely to leave the bloodstream and distribute to areas with high lipid density such as adipose tissue. - Have a higher Vd. - **Hydrophilic molecules:** - Less likely to pass through lipid bilayers. - More likely to remain in the bloodstream. - Have a lower Vd.