2-pharma-Basic-Concepts-of-Pharmacology-28.pdf

PHARMACOLOGY Basic Concepts of Pharmacology PHARMACODYNAMIC PHASE  Receptors A receptor is a protein molecule on the surface of or within a cell that recognizes and binds with specific molecules, thereby producing some effect within the cell. – rec...

PHARMACOLOGY Basic Concepts of Pharmacology PHARMACODYNAMIC PHASE  Receptors A receptor is a protein molecule on the surface of or within a cell that recognizes and binds with specific molecules, thereby producing some effect within the cell. – receptor site may have specificity – the affinity is the strength by which a particular chemical messenger binds to its receptor site or cell  Mechanisms of Drug Action Agonist An agonist is a drug that binds to a particular receptor site and triggers the cell’s response in a manner similar to the action of the body’s own chemical messenger.  Mechanisms of Drug Action Antagonist An antagonist is a drug that binds to a receptor site and blocks the action of the endogenous messenger or other drugs.  Pharmacokinetics Activity of a drug within the body over a period of time. This is the study of the mathematical relationships among the absorption, distribution, metabolism, and excretion of individual medicines over time  LIBERATION = also known as the pharmaceutic effect, relating to the dosage form being used After liberation from the dosage form, each drug has its own unique ADME  Pharmacokinetics Absorption Process whereby a drug is transferred from its site of entry into the body to the circulating fluids of the body (e.g. lymph and blood) for distribution around the body The rate at which this occurs depends on the route of administration, the blood flow through the tissue where the drug is administered, and the solubility of the drug  Pharmacokinetics Distribution Process by which a drug moves from the blood into other body fluids and tissues and ultimately to its sites of action (receptors) This may be general or selective Blood flow is the rate-limiting factor.  Pharmacokinetics Metabolism Also called biotransformation This is the process by which the body inactivates drugs Liver is the primary site of metabolism  Pharmacokinetics Elimination / Excretion Clearance is the rate at which a drug is eliminated from a specific volume of blood per unit of time.  Discussion What are the primary sites of elimination in the body?  Discussion What are the primary sites of elimination in the body? Answer: The kidney and the liver, but can also be exhaled by the lungs or excreted in perspiration.  HALF-LIFE This is defined as the amount of time required for 50% of the drug to be eliminated from the body This is essential in determining the dosage interval of a drug This is determined by an individual’s ability to metabolize and excrete a particular drug ADVERSE DRUG REACTIONS Defined by WHO as any noxious, unintended, and undesired effect of a drug, which occurs at doses used in humans for prophylaxis, diagnosis or therapy “right drug, right dose, right patient, bad effect” Should not be confused with Adverse Drug Events CAN YOU SAY SOMETHING ABOUT AN ALLERGIC REACTION? WHEN DOES THIS OCCUR?  ALLERGIC REACTION This is also known as HYPERSENSITIVITY REACTION This occurs in patients who have previously been exposed to a drug and have developed antibodies to it from their immune systems On re-exposure, the antibodies cause a reaction, most commonly seen as raised, irregularly shaped patches on the skin and severe itching, known as URTICARIA or hives.  CARDIOGENICITY This is the ability of the drug to induce living cells to mutate and become cancerous Many drugs have this potential, that is why these drugs are tested in several animal species before human investigation  TERATOGENICITY This is a drug that induces birth defects Fetal body organs are susceptible to malformation if they are exposed to a drug while in the uterus  Drug Effects Beneficial Responses – Therapeutic Effect The action for which the drug is prescribed – Local Effect Confined to a specific part of the body – Systemic Effect Generalized, all-inclusive effect on entire body  Discussion What are some of the issues a healthcare practitioner considers when selecting a drug for an individual patient?  Drug Effects When choosing a drug for a patient, a healthcare practitioner considers: Indications The diseases, symptoms, and conditions for which the drug is known to be of benefit Contraindications The diseases, symptoms, and conditions for which the drug will not be beneficial and may do harm  Drug Effects Side Effects Secondary responses to a drug other than the primary therapeutic effect for which the drug was intended  Common Drug Relationships ADDITIVE EFFECT = two drugs with the similar actions are taken for a doubled effect – Example: Propoxyphene + aspirin =added analgesic effect  SYNERGISTIC EFFECT = the combined effect of two drugs is greater than the sum of the effect of each drug given alone Example: Aspirin + codeine = much greater analgesic effect  ANTAGONISTIC EFFECT = one drug interferes with the action of another Example: Tetracycline + antacid = decreased absorption of the tetracycline  INCOMPATIBILITY = the first drug is chemically incompatible with the second drug, causing deterioration when both drugs are mixed in the same syringe or solution Example: Ampicillin + Gentamicin = ampicillin inactivates gentamicin  Discussion Why is it important for the pharmacy to have a complete list of all of the prescription drugs, OTC medications, vitamins, and herbal remedies that a patient is taking?  Discussion Why is it important for the pharmacy to have a complete list of all of the prescription drugs, OTC medications, vitamins, and herbal remedies that a patient is taking? Answer: Such a list will help healthcare professionals identify potential drug interactions.