Pharmacology Basics Study Guide

Pharmacology Basics When a drug has an effect on another drug Types: • • Behavioural Drug-drug: altering patient’s behaviour to alter compliance with a drug. For example, giving a drug that improves the symptom to make to patient more compliant with the drug Pharmaceutics drug – drug: when the formulation of one drug is altered by another before it is administrated Pharmacokinetic Drug Effects: • • • Alters bioavailability - Amount of drug that reaches systemic circulation is affect by a perpetrator drug - For oral drugs this is because absorption or first pass metabolism are altered Altered clearance - Metabolism: affects drug clearance - Drugs that inhibit CYP450 -> increase drug concentration and decrease drug metabolism ➢ +ve: allows drug to stay for longer to have its’ effect ➢ -ves: accumulation of drug in the body to toxic levels ➢ Need a lower concentration of the drug when you have an inhibitor for CYP450 drug, and you do not want for there to be too much levels - Drugs that induce CYP450 decrease drug concentration and increase drug metabolism (by increasing its’ breakdown) ➢ Need a higher concentration/dosage of the drug to achieve effect - Excretion: drugs that alter the renal tubular function or urine pH -> this reduces renal clearance of some drugs leading to the drug being excreted in its’ active form Altered Distribution - When the concentration of the drug at the site of action is altered without necessarily altering its circulating circulation - For example, when a drug changes the cell membrane transport of other drugs Pharmacodynamic Effects: • • Interactions between drugs with addictive effects or opposing effects - When for opposing effects: the action of drug is completely lost, for example when given beta 2 blockers to help with bronchodilation but also given a non-selective beta blocker - Addictives: for example, giving two antihypertensives Heparin and perindopril increase the levels of vitamin K in the body -> haemolytic anaemia Drug to food interactions • • Can make them more or less effective Food can reduce the absorption of the drug and thus decreasing the effect of the drug • • • Grapefruit: increases the effectiveness of some medications, such as cholesterol lowering medications - Makes the effects or the side effects of the medications really bad Green leafy vegetables lowers the effectiveness of blood thinning medications - This is because green leafy veggies are rich in vitamin K, which promote blood clot formation Alcohol and anti-inflammatory medications lowers the effects of anti-inflammatory medications. E.g., NSAIDS Drug - enzyme interactions • Agonist drugs - Same effect as the substrate - Bind on the same active site as the substrate Full Agonist • 100% of maximum effect Partial • Even when occupy all receptors, lower response, lower Emax Partial Agonist • Antagonist drugs - Block the effect - Competitive: binds on the same active site as the substrate - Non-competitive: binds to the allosteric site -> changes the shape of the active site -> no longer recognisable - Reversible vs irreversible: reversible when bind and then unbind, ligand is more likely to bind Competitive • Shift curve to the right, without effecting Emax, but increase ED50 -> decrease the agonist potency but not efficacy. - Note: ED50: is the dose of medication that produces half of the desired effect Non-competitive • • • • Either irreversible or dissociates very slowly Can’t be activated no matter how many agonists are around Dose response curve does not shift so ED50 will not be changed But the slope and peak decrease thus the Emax decreased Drug -receptor interactions