Introduction to Pharmacology (1) PDF

Chapter 2 Pharmacological Principles 1  Pharmacology  Drug  Any chemical that affects the physiological processes of a living organism  Pharmacology  Broadest term for the study or science of drugs...

Chapter 2 Pharmacological Principles 1  Pharmacology  Drug  Any chemical that affects the physiological processes of a living organism  Pharmacology  Broadest term for the study or science of drugs 2  Prototype Drug  a drug which represents other drugs in the same classification  the well-understood drug model by which other drugs within the same classification can be compared  when you learn the prototype drug in a classification, then you will be able to predict the actions, adverse effects, etc. of other drugs in the same classification  the original drug prototype may not always be the most widely used drug in the classification  example: penicillin V is the prototype drug in the penicillin classification. If you know the mechanism of action, adverse effects, etc. of penicillin V, then you will be able to predict the action, adverse effects, etc. of other drugs within the penicillin classification. 3  Drug Names Throughout the process of its development, a drug will acquire at least three different names: 1. Chemical name 2. Generic name (nonproprietary, official name) 3. Trade name (proprietary name) 4 Chemical, Generic, and Trade Names and Chemical Structure of Ibuprofen Which name(s) do nurses most often use? 5  Drug Classification  Drug Classification  Drugs are grouped together based on their similar properties  Drugs can be classified by their structure therapeutic use 6  Phases of Pharmacology Three basic phases of pharmacology  pharmaceutics  pharmacokinetics and  pharmacodynamics 7  Pharmaceutics  The study of how various drug forms influence the way in which the drug affects the body  Dissolution  dissolving of solid dosage forms and their absorption 8  Pharmacodynamics  is the study of what the drug does to the body 9  Pharmacokinetics (1 of 14)  The study of what the body does to the drug  From the time drug is put into the body until the parent drug and metabolites have left the body  Absorption  Distribution  Metabolism  Excretion 10  Pharmacokinetics (2 of 14)  Absorption  Bioavailability:  First-pass effect:  Routes: Enteral route Parenteral route: Sublingual and buccal  Intradermally  subcutaneously routes  Intravenously Topical route  Intramuscularly Transdermal route  Intrathecally Inhalation route  intra-articularly  intra-arterially 11  First Pass Effect Considerations:  How does first pass effect alter the bioavailability of drugs?  How does first pass effect alter the dosage of drugs? 12  Enteral Route  The drug is absorbed into the systemic circulation through the mucosa of the stomach, small intestine, or large intestine  Oral  Sublingual  Buccal  Rectal (can also be topical) 13  Parenteral Route  Intravenous  fastest due to direct delivery into the blood circulation  Intramuscular  Subcutaneous  Intradermal  Intra-arterial  Intrathecal  Intra-articular 14  Topical Route  Skin (including transdermal patches)  Eyes  Ears  Nose  Lungs (inhalation)  Rectum  Vagina 15  Pharmacokinetics (3 of 14)  Distribution  Transport of a drug by the bloodstream to the drug’s site of action  Drugs distributed first to areas with extensive blood supply Heart, liver, kidneys and brain 16 Pharmacokinetics (4 of 14) 17  Pharmacokinetics (5 of 14)  Albumin is the most common blood protein and carries the majority of protein-bound drug molecules.  If a given drug binds to albumin, only a limited amount of the drug is not bound.  This unbound portion is active and is considered “free” drug. 18 Pharmacokinetics (6 of 14) 19  Pharmacokinetics (7 of 14)  Metabolism Also referred to as biotransformation Biochemical alteration of a drug into any of the following:  an inactive metabolite  a more soluble compound  a more potent metabolite (as in the conversion of an inactive prodrug to its active form)  a less active metabolite 20  Pharmacokinetics (8 of 14)  Hepatic metabolism involves a large class of enzymes the - Cytochrome P-450 enzymes (or simply P-450 enzymes), also known as microsomal enzymes  These enzymes control a variety of reactions that aid in the metabolism of medications. 21  Pharmacokinetics (9 of 14)  Excretion Elimination of drugs from the body Primary organ responsible is kidney Liver and bowel also play a role Renal excretion Biliary excretion 22 Pharmacokinetics (10 of 14) 23  Pharmacokinetics (11 of 14)  Half-life: time required for half (50%) of a given drug to be removed from the body  Steady state  Onset of action  Peak effect  Duration of action 24  Pharmacokinetics (12 of 14)  The length of time until the onset and peak of action and the duration of action play an important part in determining the peak level (highest blood level) and trough level (lowest blood level) of a drug. If the peak blood level is too high, then drug toxicity may occur. 25 Pharmacokinetics (13 of 14) 26  Pharmacokinetics (14 of 14)  Peak level: highest blood level of a drug  Trough level: lowest blood level of a drug  Toxicity: occurs if the peak blood level of the drug is too high  Therapeutic drug monitoring 27  Loading vs. maintenance dose Loading Dose  a higher amount of the drug is given, often only once or twice to increase the drug level in the bloodstream with a level sufficient to induce a therapeutic response Maintenance Dose  intermittent doses of the drug are given to maintain a therapeutic level of the drug in the bloodstream 28  Pharmacodynamics (1 of 2)  The study of what the drug does to the body  The mechanism of drug actions in living tissues  Therapeutic effect The goal of drug therapy  Mechanism of action***  Receptor interactions  Enzyme interactions 29  Pharmacodynamics (2 of 2)  Figure 2-8, Drugs act by forming a chemical bond with specific receptor sites, similar to a key and lock—the better the “fit,” the better the response. Drugs with complete attachment and response are called agonists. Drugs that attach but do not elicit a response are called antagonists. Drugs that attach, elicit some response, and also block other responses are called partial agonists or agonist–antagonists 30 Drug Plasma Concentration and Therapeutic Response  the therapeutic response of most drugs is directly related to their concentration in the plasma  lab tests can be done that measure the serum level of drugs Define:  minimum effective concentration  toxic concentration  therapeutic range 31  Pharmacotherapeutics (1 of 5)  The clinical use of drugs to prevent and treat diseases  Desired therapeutic outcomes is patient- specific, established in collaboration with the patient.  Outcome goals need to be realistic. 32  Pharmacotherapeutics (2 of 5)  Contraindications  Types of Therapy  Acute  Maintenance  Supplemental (or replacement)  Palliative  Supportive  Prophylactic  Empirical 33  Pharmacotherapeutics (3 of 5)  Monitoring  Therapeutic action Beneficial effects  Adverse effects Predictable adverse drug reactions  Toxic effects  Therapeutic index  Drug concentration  Patient condition 34  Pharmacotherapeutics (4 of 5)  Tolerance: decreasing response to repeated drug doses  Dependence: physiological or psychological need for a drug  Physical dependence:  physiological need for a drug to avoid physical withdrawal symptoms  Psychological dependence (addiction):  obsessive desire for a drug 35  Pharmacotherapeutics (5 of 5)  Drug interactions  Additive effects  Synergistic effects  Antagonistic effects  Incompatibility 36  Reference  Sealock, K., Seneviratne, C., Lilley, L. L., & Synder, J.S. (2020). Lilley's Pharmacology for Canadian Health Care Practice (4th ed.). Milton, ON: Elsevier, Canada 37