Pharmacology_Introduction.pptx

Pharmacol ogy Noreen V. Borres, RN, LPT, MANc Clinical Instructor Chapter 1 - Introduction to Pharmacolo gy OVERVIEW ⚫ What is PHARMACOLOGY? OVERVIEW ▶Pharmacology is the study of drugs (chemicals) that alter functions of living organisms. ▶Drug therapy, also called pharmacothera...

Pharmacol ogy Noreen V. Borres, RN, LPT, MANc Clinical Instructor Chapter 1 - Introduction to Pharmacolo gy OVERVIEW ⚫ What is PHARMACOLOGY? OVERVIEW ▶Pharmacology is the study of drugs (chemicals) that alter functions of living organisms. ▶Drug therapy, also called pharmacotherapy, is the use of drugs to prevent, diagnose, or treat signs, symptoms, and disease processes. ▶Drugs given for therapeutic purposes are usually called medications. PHARMACOTHERAPEUTICS ⚫ is the branch of pharmacology that uses drugs to treat, prevent and diagnose. PHARMACODYNAM ICS ⚫ Study of biochemical and physiological effects of drugs; study of drugs mechanism of action. PHARMACOKINETICS ⚫ Study of the absorption, distribution, and biotransformation (metabolism) and excretion of drugs. PHARMACOGNOSY ⚫ Study of drugs derived from herbal and other natural sources. TOXICOLOGY ⚫ Study of poisons and poisoning. ⚫ involves the study of the adverse effects of chemical substances on living organisms and the practice of diagnosing and treating exposures to toxins and toxicants. SOURCES OF DRUGS ⚫ Plants ⚫ Animals ⚫ Minerals ⚫ Synthetic chemical ⚫ Microbiological SOURCES OF DRUGS ⚫ Plant Sources: ◦Plant source is the oldest source of drugs. ◦Most of the drugs in ancient times were derived from plants. ◦Almost all parts of the plants are used i.e. leaves, stem, bark, fruits and roots. SOURCES OF DRUGS ⚫ Plant Sources: ◦The leaves of Digitalis Purpurea are the source of Digitoxin and Digoxin, which are cardiac glycosides. ◦Poppy papaver somniferum gives morphine (opoid) SOURCES OF DRUGS ⚫ Animal Sources: ◦Pancreas is a source of Insulin, used in treatment of Diabetes. ◦Cod liver is used as a source of vitamin A and D ◦Blood of animals is used in preparation of vaccines. SOURCES OF DRUGS ⚫ Mineral Sources: ◦Iron is used in treatment of iron deficiency anemia. ◦Gold salts are used in the treatment of rheumatoid arthritis. ◦Iodine is antiseptic. Iodine supplements are also used. SOURCES OF DRUGS ⚫ Synthetic Sources: ◦When the nucleus of the drug from natural source as well as its chemical structure is altered, ◦Majority of drugs used in clinical practice are prepared synthetically, such as aspirin, oral antidiabetics, antihistamines, amphetamine, chloroquine etc. SOURCES OF DRUGS ⚫ Microbiological Sources: ◦Penicillium notatum is a fungus which gives penicillin. ◦Actinobacteria give Streptomycin. ◦Aminoglycosides such as gentamicin and tobramycin are obtained from DRUG CLASSIFICATIONS ⚫ Drugs are classified according to their effects on particular body systems, their therapeutic uses. A. PRESCRIPTION DRUGS ▶Are those that have on their labels the prescription legend. ▶May be prescribed by the physicians, dentists, veterinarians, or other legally authorized health practitioner as part of their specific practice. B. NON-PRESCRIPTION DRUGS ⚫ The drugs that may be legally acquired by the client without the prescription order. ⚫ Also known as over the counter drugs (OTC) C. INVESTIGATIONAL DRUGS ⚫ The term that refers to drugs that have received FDA approval for human testing, including those drugs still undergoing clinical trials , but are not approved for marketing to the general public. D. ORPHAN DRUG ⚫ Are drugs that have been discovered but are not financially viable and therefore have not been “adopted” by any drug company. E. ILLICIT DRUG ⚫ a.k.a. “street’ drugs are those which are used and/or distributed illegally. ⚫ ellicit drugs refer to highly addictive and illegal substances such as heroin, marijuana and meth Legal Regulation of Drugs ⚫ A. FDA Pregnancy Categories ⚫ B. Controlled Substances A. FDA Pregnancy Categories Category A ▶Adequate studies in pregnant women have NOT demonstrated a risk in the fetus in the first trimester of pregnancy and there is no evidence of risk in later trimester. Category B ▶Animal studies have NOT demonstrated a risk for the fetus but there are No adequate studies in pregnant women, or animal studies have shown an adverse effect, but adequate studies in pregnant women have not demonstrated a risk to the fetus during the first trimester, and there is no evidence of risk on later trimester. Category C ▶Animal studies have shown an adverse effect on the fetus but there are no adequate studies in humans, the benefits from the use of the drug in pregnant women may be acceptable despite the potential risks, or there are no animal reproduction studies and no adequate studies in humans. Category D ▶There is evidence of human fetal risk, but the potential benefits from the use of the drug in pregnant women may be acceptable despite of its potential risks. B. Controlled Substances Schedule I ▶Drugs that are not approved for medical use and have high abuse potentials ▶E.g. heroin, lysergic acid diethylamide (LSD), peyote, mescaline, tetrahydrocannabinol, marijuana. Schedule II ▶Drugs that are used medically and have high abuse potentials ▶opioid analgesics (eg, codeine, hydromorphone, methadone, meperidine, morphine, oxycodone, oxymorphone), ▶central nervous system (CNS) stimulants (eg, cocaine, methamphetamine, methylphenidate) ▶barbiturate sedative-hypnotics (amobarbital, pentobarbital, secobarbital). Schedule III ▶Drugs with less potential for abuse than those in Schedules I and II, but abuse may lead to psychological or physical dependence ▶androgens and anabolic steroids, ▶some CNS stimulants (eg, benzphetamine), and mixtures containing small amounts of controlled substances (eg, codeine, barbiturates not listed in other schedules).  Schedule IV ▶Drugs with some potential for abuse: ▶benzodiazepines (eg,diazepam, lorazepam, temazepam), ▶other sedative-hypnotics (eg, phenobarbital, chloral hydrate), and ▶some prescription appetite suppressants (eg, mazindol, phentermine).  Schedule V ▶Products containing moderate amounts of controlled substances. ▶They may be dispensed by the pharmacist without a physician’s prescription but with some restrictions regarding amount, record keeping, and other safeguards. ▶Included are antidiarrheal drugs, such as diphenoxylate and atropine (Lomotil). CLASSIFICATIONS ▶ Antipyretic ▶ Decongestants ▶ Analgesics ▶ Diuretics ▶ Antibiotics ▶ Emetics ▶ Antidepressants ▶ Expectorants ▶ anti-hypertensives ▶ Hypnotics ▶ anti-diabetic ▶ Laxatives ▶ Antihistamine ▶ Sedatives ▶ Antitussive ▶ Tranquilizers ▶ cholinergics ▶ Antipsychotic DRUG NAMES ▶Individual drugs may have several different names, but the two most commonly used are the ▶GENERIC NAME and the ▶TRADE NAME (also called the brand or proprietary name). ⚫ The GENERIC NAME (eg, amoxicillin) is related to the chemical or official name and is independent of the manufacturer. ⚫ Differentiated from Trade Name by initial lowercase letter; NOT CAPITALIZED… ▶The TRADE NAME is designated and patented by the manufacturer. ▶CAPITALIZED FIRST LETTER ▶For example, amoxicillin is manufactured by several pharmaceutical companies, some of which assign a specific trade name (eg, Amoxil, Trimox) ▶CHEMICAL NAME is the exact molecular formula of the drug; usually a long, very difficult name to pronounce and of a little concern to the health care worker. ⚫ OFFICIAL NAME is the name of the drug as it appears in the official reference, the USP/NF; generally the same as the generic name. GENER TRADE NAME IC NAME ibuprofen Advil lorazepam Ativan diphenhydramine Benadryl captopril Capoten GEN ER IC TRADE NAME NAME Clonidine Catapres Celecoxib Celebrex metformin Glucophage misoprostol Cytotec PRESCRIPTION AND NONPRESCRIPTION DRUGS ▶Legally, consumers have two routes of access to therapeutic drugs. ▶One route is by PRE SCRIPTION or order from a licensed health care provider, such as a physician, dentist, or nurse practitioner. ▶The other route is by OVER-THE- COUNTER (OTC) purchase of drugs that do not require a prescription. DRUG APPROVAL PROCESSES ▶The FDA (Food and Drug Administration) is responsible for assuring that new drugs are safe and effective before approving the drugs and allowing them to be marketed. Testing and Clinical Trials ⚫ The testing process begins with animal studies to determine potential uses and effects. ⚫ Clinical trials, also known as clinical studies, test potential treatments in human volunteers to see whether they should be approved for wider use in the general population. ⚫ A treatment could be a drug, medical device, or biologic, such as a vaccine, blood product, or gene therapy. ▶ InPhase I, a few doses are given to a few healthy volunteers to determine safe dosages, routes of administration, absorption, metabolism, excretion, and toxicity. ▶ InPhase II, a few doses are given to a few subjects with the disease or symptom for which the drug is being studied, and responses are compared with those of healthy subjects. ▶ InPhase III, the drug is given to a larger and more representative group of subjects. ⚫ In phase IV, after a drug is approved for marketing, it enters a phase of continual evaluation. TERMS INDICATING DRUG ACTION INDICATIONS ⚫ A list of medical conditions or diseases for which the drug is meant to be used. ACTIONS ⚫ A description of the cellular changes that occur as a result of the drug. CONTRAINDICATIONS ⚫ A list of conditions for which the drug should not be given. SIDE EFFECTS and ADVERSE REACTIONS ⚫ A list of possible unpleasant or dangerous effects, other than the desired effects, INTERACTIONS ⚫ A list of other drugs or foods that may alter the effects of the drug and usually should not be given during the same course of therapy. DRUG ACTION: Pharmaceutic, Pharmacokinetic & Pharmacodynamic Phases  A. Pharmaceutic Phase The first phase of drug action Drug becomes a solution so that it can be absorbed 2 Pharmaceutic phases: Disintegration & Dissolution Disintegration – is the breakdown of a tablet into smaller particles Dissolution – is the dissolving of the smaller particles in the GI  Factors Affecting Pharmaceutic phase pH Drugs are both disintegrated and absorbed faster in acidic fluids than alkaline fluids Age Both very young and elderly have less gastric acidity.Therefore, drug absorption is generally slower  Factors Affecting Pharmaceutic phase Enteric-coated tablets/capsules Resist disintegration in the gastric acid of the stomach Disintegration only happens in the alkaline environment of the small intestine Enteric-coated tablets or capsules and sustained-release (beaded) capsules should not Factors Affecting Pharmaceutic phase Food may interfere with the dissolution and absorption of certain dugs in the GIT Can also enhance absorption of other drugs B. Pharmacokinetic Phase The of drug movement to achieve drug action The Process are: ABSORPTION DISTRIBUTIO N METABOLISM EXCRETION B. Pharmacokinetic Phase Pharmacokinetics involves drug movement through the body (ie, “what the body does to the drug”) to reach sites of action, metabolism, and excretion.  ABSORPTI OAbsorption N is the process that occurs from the time a drug enters the body to the time it enters the bloodstream to be circulated. Is the movement of drug particles from the GI tract to body fluids by passive absorption, active absorption, or Pinocytosis  ABSORPTI OMost N oral drugs are absorbed into the surface area of the small intestine through the action of mucosal villi Absorption is reduced if the villi are decreased in number because of disease, drug effect or removal of small intestine 3 Major Process of drug Passive absorption – occurs Absorption mostly by diffusion (movement from higher concentration to lower concentration) Active absorption – requires a carrier such as enzyme or protein to move the drug against a concentration agent Pinocytosis – is a process by which cells carry a drug across  FACTORS AFFECTING BLOOD FLOW A B S–Opoor R P Tcirculation ION as a result of shock, vasoconstrictor drugs, or disease hampers absorption PAIN, STRESS & FOODS – slows gastric emptying time, so the drug remains in the stomach longer EXERCISE – decreases blood flow by causing more blood to flow to the peripheral muscle, thereby decreasing blood circulation to the GI tract BLOOD SUPPLY – drugs given IM are absorbed faster in muscles that have more blood vessels (e.g. deltoids) than in those  FIRST PASS EFFECT – the process in which the drug passes to the liver first, metabolizing the drug to an inactive form which may then be excreted. E.g.Warfarin (Coumadin) and Morphine DRUG SOLUBILITY – Lipid soluble drugs pass rapidly through GI membrane and water soluble drugs need a carrier to pass through the membrane BIOAVAILABILI Is a subcategory of absorption TY is the percentage of the administered drug dose that reaches the systemic circulation after absorption and hepatic metabolism (less than 100% for oral route, 100% for IV route) Ex: if 100mg of drug is administered orally and 70mg of this drug is absorbed unchanged, the bioavailability is 70 %. Factors Affecting Bioavailability Drug form Route of administration GI mucosa and motility Food and other drugs Changes in liver metabolism caused by liver dysfunction DIS TRI B U TI ON The process by which the drug becomes available to body fluids and body tissues Influenced by blood flow, drug’s affinity to the tissue and the protein- binding effect Protein binding effect - Drugs that binds to a carrier protein (albumin) is pharmacologically becomes DIS TRI B U TI ON Only “free drugs” (drugs not bound to protein) are active and can cause pharmacologic response As the free drug in the circulation decreases, more bound drug is released from the protein to maintain the balance of free drug DIS TRI B U TI ON Once a drug is injected or absorbed into the bloodstream, it is carried by the blood and tissue fluids to its sites of pharmacologic action, metabolism, and excretion Distribution depends largely on the adequacy of blood circulation DIS TRI B U TI ON Drugs are distributed rapidly to organs receiving a large blood supply, such as the liver, heart, and kidneys. Distribution to other internal organs, muscle, fat, and skin is usually slower.  DISTRIB UT IO N Protein-Binding 1.Highly Protein-Bound Drugs >89% of the drugs are bound to protein E.g. diazepam, furosemide, ibuprofen, propanolol 2.Moderately Highly Protein- Bound drugs that are 61%-89% bound to protein  DI STRI B U TI ON Protein-Binding 3.Moderately Protein-Bound Drugs Drugs that are 30-60% bound to protein E.g. aspirin, lidocaine, meperidine, theophylline 4.Low Protein-Bound Drugs Drugs that are less than 30% DI S TRI B U T I ON ⚫ Clients with liver or kidney disease, those who are malnourished may have an abnormally low serum albumin level ⚫ This results in fewer protein- binding sites, which in turn leads to excess free drug and drug toxicity DI S TRI B U T I ON ⚫ Drug distribution into the central nervous system (CNS) is limited because the blood–brain barrier, which is composed of capillaries with tight walls, limits movement of drug  DI S TRI B U T I ON ⚫ Drug distribution during pregnancy and lactation is also unique. ⚫ During pregnancy, most drugs cross the placenta and may affect the fetus. ⚫ During lactation, many drugs enter breast milk and  METABOLISM Aka.“Biotransformation” The process by which a drugs are inactivated by liver enzymes and are then converted into inactive Liver is the primary site of metabolism  METABOLI SM Most drugs are inactivated by liver enzymes and are then converted or transformed by hepatic enzymes to inactive metabolites or water soluble substances for Excretion Liver diseases such as cirrhosis and hepatitis alter drug metabolism by inhibiting the drug metabolizing enzymes in the liver  METABOLI SM When the drug metabolism rate is decreased, excess drug accumulation can occur and lead to toxicity However, the kidneys, which are the primary excretory organs, can excrete only water-soluble substances. Therefore, one function of metabolism is to convert fat- soluble drugs into water- soluble  METABOLISM Some drugs are extensively metabolized in the liver, with only part of a drug dose reaching the systemic circulation for distribution to sites of action. This is called the first-pass effect or presystemic metabolism METABOLISM HALF LIFE – is the time it takes for one half of the drug concentration to be eliminated  A short half-life is 4 to 8 hours  A long half-life is 24 hours or more  A drug with long half-life takes several days for the body to completely eliminate the drug  Half-life of 650 mg of Aspirin Time of Dosages Percenta eliminati Remaini ge Left on ng (mg) (%) (hours) 3 325 50 6 162 25 9 81 12.5 12 40 6.25 15 20 3.1 18 10 1.55 E XC R E T I O Refers N to the elimination of drugs from the body K I D N E Y – is the main route of drug elimination Other routes: hepatic metabolism, bile, feces, lungs, saliva, sweat & breast milk E XC R E T I O N Effective excretion requires adequate functioning of the circulatory system and of the organs of excretion (kidneys, bowel, lungs, and skin) Most drugs are excreted by the kidneys as urine. Some drugs or metabolites are excreted in bile, then eliminated in feces E XC R E T I O N lungs mainly remove The volatile substances, such as anesthetic gases. The skin has minimal excretory function. Factors Affecting E XC R E T I O N Urine pH Urine pH varies from 4.5 – 8 Acidic urine promotes elimination of weak base drugs Alkaline urine promotes elimination of weak acid drugs e.g. aspirin Factors Affecting E XC R E T I O N Kidney Diseases Results in decrease glomerular filtration rate (GFR) – decrease drug excretion causing drug accumulation (drug toxicity) C. Pharmacodynamic Phase Is the study of drug concentration and its effects on the body The study of the mechanisms of drug action that produce biochemical or physiologic changes in the body C. Pharmacodynamic Phase Pharmacodynamics involves drug actions on target cells and the resulting alterations in cellular biochemical reactions and functions (ie, “what the drug does to the body”). As previously stated, all drug actions occur at the cellular level C. Pharmacodynamic Phase Drug response can cause a primary or secondary physiologic effect or both E.g. Diphenhydramine (Benadryl) – antihistamine, primary effect is treat symptoms of allergy, secondary effect – CNS depression that causes drowsiness ONSET, PEAK & D U R AT I O N of Action 1.ONSET OF ACTION – is the time it takes to reach the minimum effective concentration after a drug is administered 2.PEAK ACTION – occurs when the drug reaches its highest blood or plasma concentration 3.DURATION OF ACTION – is Receptor Most receptors, protein in Theory structure are found on cell membranes Drugs act through receptors by binding to the receptor to produce (initiate) a response or to block (prevent) a response. Receptor The activity of Theory many drugs is determined by the ability of the drug to bind to a specific receptor, “the better the drug fits at the receptor site, the more biologically active the drug is” (similar to lock and key AGONISTS & A N TA G O N I S AGONISTS –T S that drugs produce a response ANTAGONISTS – drugs that block a response E.g. Isoproterenol (Isuprel) simulates the beta 1 receptor (agonist), Cimetidine (Tagamet), an antagonist, blocks the histamine (H2) receptor, thus preventing excessive gastric acid secretion Categories of Drug Action The four categories of drug action include 1. Stimulation or depression 2. Replacement 3. Inhibition or killing of organisms, and 4. Irritation Categories of Drug Action In drug action that stimulates, the rate of cell activity or the secretion from a gland increases. In drug action that depresses, cell activity and function of a specific organ are reduced Replacement drugs such as insulin replace essential body compounds. Categories of Drug Action Drugs that inhibit or kill organisms interfere with bacterial cell growth (e.g., penicillin exerts its bactericidal effects by blocking the synthesis of the bacterial cell wall). Drugs also can act by the mechanism of irritation (e.g., laxatives irritate the inner wall of the colon, thus increasing peristalsis and defecation). TH ERAP EUT I C I NTherapeutic DEX Index (TI) – estimates the margin of safety of a drug through the use of a ratio that measures the effective (therapeutic) dose (ED) in 50% of people and lethal dose (LD) in 50% of people The closer the ratio to 1, the greater the danger of toxicity Formula: TH ERAP EUT I C I NFor DE X example, if the LD50 is 200 and the ED50 is 20 mg, the TI would be 10. TI = LD50 = 200 = 10 ED50 20 A clinician would consider a drug safer if it had a TI of 10 than if it had a TI of 3 TH ERAP EUT I C I NLOW D E XTHERAPEUTIC INDEX – have a narrow margin of safety, drug levels need to be monitored; drug dosage might need adjustment HIGH THERAPEUTIC INDEX – have a wide margin of safety and less danger of producing toxic effects TH ERAP EUT I C I NTherapeutic DEX range (therapeutic window) of a drug in plasma is the level of drug between the minimum effective concentration in the plasma for obtaining desired action and the minimum toxic concentration (the toxic effect) If therapeutic range is narrow, such as digoxin (0.5 to 1ng/ml), the plasma drug level should be PEAK & T R O U G H D R U G LEVEL PEAK D R U G LEVEL Is the highest plasma concentration of drug at a specific time Indicates the rate of absorption Drug given orally – 1-3 hours of peak time after drug administration Drugs given by IV – 10 minutes PEAK & T R O U G H D R U G LEVEL T R O U G H D R U G LEVEL Is the lowest plasma concentration of a drug and it measures the rate at which the drug is eliminated Trough levels are drawn immediately before the next dose of drug is given PEAK & T R O U G H D R U G LEVEL Peak and trough levels are requested for drugs that have a narrow therapeutic index and considered toxic i.e. aminoglycoside antibiotics Serum Drug Levels ⚫ A serum drug level is a laboratory measurement of the amount of a drug in the blood at a particular time. ⚫ It reflects dosage, absorption, bioavailability, half-life, and the rates of metabolism and excretion. Serum Drug Levels ⚫ A toxic concentration is an excessive level at which toxicity occurs. ⚫ Toxic concentrations may stem from ◦single large dose, ◦repeated small doses, ◦slow metabolism that allows the drug to accumulate in the body Types of drug therapy: ⦿ Acute Therapy ◦ For critically ill patients who requires acute intensive care ◦ E.g. Vasopressors – maintain BP and CO,Volume Expanders – shock; Antibiotic – trauma patient high risk for infection Types of drug therapy: ⦿ Maintenance Therapy ◦ For a patient with a chronic condition who needs to maintain his level of well- being ◦ E.g. Antihypertensive drugs – maintain blood pressure, Oral contraceptive – birth control Types of drug therapy: ⦿ Supportive Therapy ◦ Maintains the integrity of body functions while patient is recovering from illness or trauma ◦ E.g. Fluid and Electrolytes – for dehydration secondary to diarrhea and vomiting , blood products – for patient who lost blood during surgery Types of drug therapy: ⦿ Palliative Therapy ◦ For a patient with an end- stage or terminal disease to make him as comfortable as possible ◦ E.g. high dose Opioid analgesics- relieve pain in the final stage of cancer, Use of oxygen therapy – end stage pulmonary disease Types of drug therapy: ⚫ Empiric Therapy ◦Based on practical experience rather than on pure scientific data ◦E.g. Acetaminophen – given to a patient for fever even the cause of fever is not known  Types of drug ⚫therapy: Supplemental or Replacement Therapy ◦Replenishes or substitutes for missing substances in the patient’s body ◦Substances is needed either because it cannot be made by the body or it is produced in insufficient quantity ⦿Prophylactic Therapy ⚫ Provided to prevent illness or undesirable outcome ⚫ E.g. malarial drug – before entering malarial endemic area ⚫ Antibiotic therapy – patient who has incision on the skin and for possibility of bacterial invasion  IMPORTANT ⚫TERMS: Pharmacology ◦ The study of the biological effects of chemicals ◦ The study of drugs, their uses (pharmacology) ,various dosage forms (Pharmaceutics) how the body responds to drugs (pharmacodynamics) and the absorption, distribution, metabolism and excretion of drugs (pharmacokinetics) are essential for the safe administration of drugs ⚫ Drugs  LOA D I N G D O S E  a large initial dose to initiate immediate drug response or achieve a rapid minimum effective concentration in the plasma  After a large initial dose, a prescribed dosage per day is ordered  SIDE EFFECTS  are physiologic effects not related to desired drug effects ADVERSE R E A C T I O N S  are more severe than side effects, undesirable effects of drugs that cause mild to severe side effects  Drug Names and Classes: ⚫ Chemical name ◦ The scientific name that precisely describes its atomic and molecular structure ⚫ Generic name ◦ Nonproprietary name ◦ Typically is an abbreviation of its chemical name ⚫ Trade Name ◦ Also known as the brand or proprietary name selected by the drug manufacturer  Classification of Drug: ⚫ Pharmacologic ◦ Chemical class ◦ Drugs are grouped according to the same chemical characteristics ⚫ Therapeutic ◦ Drugs are classified according to their function or the disorder they treat Example: All drugs used to treat hypertension belong to the same therapeutic class even if they belong to different pharmacologic classes.  Classification of Drug: ⚫ Exampl e: ◦Losarta n 🞄 Therap eutic class: Antihy IMPORTANT TERMS: TOXIC EFFECTS or TOXICITY  drug level exceeds the therapeutic range resulting from overdosing or drug accumulation TOLERANCE  refers to a decreased responsiveness over the course of therapy IMPORTANT TERMS: ADDITIVE EFFECTS  Occurs when two drugs with similar actions, combining them at reduced doses produces an effect equal to a higher dose  E.g. combining 2 different analgesics such as Aspirin and Codeine (Opioid) IMPORTANT TERMS: SYNERGISTIC EFFECTS  Happens if two drugs with the same effect produce a greater response when given together than when taken alone  E.g. Combining Hydrochlorothiazide and Enalapril for the treatment of Hypertension IMPORTANT TERMS: PLACEBO EFFECT  is a psychologic benefit from a compound that may not have the chemical structure of a drug effect  Sometimes patients given a placebo treatment will have a perceived or actual improvement in a medical condition POTENTIATION  The effect of drug which enhances the actions or effect of the other IMPORTANT ANTAGONISTIC EFFECT TERMS:  Develops when the combined response of two drugs is less than the response produced by either drug alone Opposite of potentiation  E.g An Antacid given with tetracycline – results in decreased absorption of the tetracycline IMPORTANT TERMS: DRUG-DRUG INTERACTION  the effects of a combination of drugs may be greater than, equal to, or less than the effects of a single drug FOOD-DRUG INTERACTION  the effects of selected foods may speed, delay or prevent absorption of specific drugs