Fundamental Concepts of Pharmacology PDF

PHARMACOLOGY 4 PROCESSES: ABSORPTION Fundamental Concepts of DISTRIBUTION PHARMACOLOGY METABOLISM/ BIOTRANSFORMATION...

PHARMACOLOGY 4 PROCESSES: ABSORPTION Fundamental Concepts of DISTRIBUTION PHARMACOLOGY METABOLISM/ BIOTRANSFORMATION EXCRETION/ ELIMINATION PHARMACOLOGY A branch of biomedical science, ABSORPTION encompassing clinical pharmacology, For a drug to be absorbed and used by that is concerned with the effects of the body, it drugs/ pharmaceuticals and other must first pass through various xenobiotics on living systems, as well as anatomical barriers. their development and chemical Refers to the movement of drug properties. particles from the GI tract to body fluids by passive A pharmaceutical drug, also called absorption, active medicine, is a chemical substance used absorption or pinocytosis. to treat, cure, prevent or diagnose a disease or to promote well-being Other factors that affect absorption: Lipid/ water solubility PHASES OF DRUG ACTION Ionization Acidity of the stomach Pharmaceutic Phase Blood flow Pharmacokinetic Phase pH Pharmacodynamic Phase Presence/absence of food Pain / Stress PHASES OF DRUG ACTION First-Pass Effect/ Hepatic First Pass- the process in which the drug passes to A process where drugs in solid form the liver first (tablet or capsule) must disintegrate into Bioavailability- percentage of the small particles to dissolve into liquid. administered drug dose that reaches the DISINTEGRATION- breakdown of a systemic circulation. Factors that tablet into affects include the drug form, route, GI smaller particles mucosa, food and other drugs and DISSOLUTION- dissolving of the changes in liver metabolism. smaller particles in the GI fluid before absorption DISTRIBUTION The process by which the drug PHARMACOKINETIC PHASE becomes available to body fluids and Process of drug movement to achieve body tissues. drug action This phase describes the time course Only free drugs(drugs that are not and disposition of a bound to protein) are active and can drug in the body, based on its cause a pharmacologic response absorption, distribution, metabolism and elimination. When two highly-protein drugs are given concurrently, they compete for protein-biding sites, thus causing Peak action- highest plasma more free drug to be released in the concentration circulation. Duration of action- length of time the drug has a pharmacologic effect METABOLISM Liver- primary site of metabolism Receptor theory: The liver metabolizes lipid-soluble – Cell membrane embedded enzymes drugs to water soluble drugs for – Ligand-gated ion channels excretion. However, some drugs are – G protein-coupled receptor systems transformed into active metabolites. – Transcription factors Half-life- time it takes for one half of the drug PHARMACODYNAMIC PHASE concentration to be eliminated Agonists- drugs that produce a response EXCRETION Antagonists- drugs that block Kidney- main route of drug elimination a response Factors that affect drug excretion: – Urine pH A receptor produces a variety of – Kidney disease physiologic responses, depending on where that receptor is located Nonspecific drugs affect various sites PHARMACODYNAMIC PHASE Nonselective drugs affect various It is the study of drug concentration receptors and its effects on the body. PHARMACODYNAMIC PHASE Primary effect- desirable; Secondary Categories of drug action: effect- either 1. Stimulation or depression desirable or not 2. Replacement No drug exerts a simple isolated action 3. Inhibition or killing of organisms solely on the diseased part of an 4. Irritation abnormal organ PHARMACODYNAMIC PHASE Dose Response- relationship between Therapeutic Index(TI)- estimates the minimal versus the maximal amount the margin of a drug through the of drug dose needed to produce the use of a ratio that measures the desired drug response effective dose (ED) and lethal dose All drugs have a maximum drug effect (LD). The closer the ratio is to 1, (maximal the greater the danger of toxicity efficacy) Peak drug level- highest plasma PHARMACODYNAMIC PHASE concentration of drug Onset of action- the time it takes to at a given time and indicate rate of reach the minimum effective absorption of drug concentration (MEC) after a drug is Trough level- lowest plasma administered concentration and measures the rate at which drug is eliminated  Loading dose- initial dose given to Pharmacodynamics: achieve rapid MEC in the plasma Onset, Peak, Duration Side effects- physiologic effects not Therapeutic Range related to the desired drug effect Side Effects, Adverse Reactions Adverse reactions- more severe than side effects; range of untoward effects of LEGISLATION-CONTROLLED SUBSTANCES drugs that cause mild to severe effects A drug or other substance that is tightly including anaphylaxis. controlled by the government because it Tachyphlaxis- drug tolerance to a may be abused or cause addiction. frequently repeated administration of a Controlled substances include opioids, certain drug stimulants, depressants, hallucinogens, and anabolic steroids. PHARMACODYNAMIC PHASE Controlled substances such as Placebo effect- physiologic benefit morphine, Valium, and Ritalin are from a compound available only by prescription from a that may not have the chemical structure licensed medical professional. of a drug effect. Pharmacogenetics- effect of drug action that varies GENERIC DRUGS from a predicted drug response because A generic drug is a pharmaceutical of genetic factors or hereditary drug that contains influence. the same chemical substance as a drug that was originally protected by patents. DETERMINANTS THAT AFFECT Generic drugs marketed without brand DRUG THERAPY names are Administration: generally less expensive than brand- Clinical Factors: name drugs, even Age and Weight though they are chemically identical to Present Health Disorder brand-name Other Disease Entities drugs and meet the same standards Client Drug Compliance ORPHAN DRUGS Pharmacokinetics: Absorption An orphan drug is a pharmaceutical Distribution (PB) agent developed to treat medical Metabolism (t1/2) conditions which, because they are so Excretion rare, would not be profitable to produce without government assistance. DRUG Drug Form ORPHAN DRUGS Route Multiple Drug Therapy Over-the counter (OTC) drugs are Drug Interactions medicines sold directly to a consumer without a prescription from a healthcare professional  NURSING IMPLICATIONS Recognize that drugs in liquid form are absorbed faster than those in solid form Assess for signs and symptoms of drug toxicity when giving two drugs that are highly protein bound Identify side effects of drugs that are nonspecific Check peak levels and trough levels of drugs that have a narrow therapeutic range Advise client not to eat fatty foods before ingesting enteric-coated tablet Check the drug literature for the protein-binding percentage of the drug Report to health care provider if drugs with a long half life are given more than once a day