Drug interactions Flashcards
Classify drug-drug interactions
Behavioural drug-drug= drug alters behaviour to modify compliance. E.g. antidepressant makes person more compliant.
Pharmaceutical drug-drug= formulation of one drug is altered by another before it is administered.
Pharmacokinetic drug-drug= one drug changes systemic concentration of another drug. bioavailability (metabolism), distribution (cell membrane transport), clearance (excretion of active, e.g. warfarin or CYP)
Steps to prevent drug-drug interactions
Recognise drugs that are major contributors of interactions
Recognise NTI drugs
Apply pharmacology principles
Get familiar with resources for drug-drug interactions
E.g. and effect of complementary medicine interactions
CYP450 or efflux P-glycoprotein
St Johns wort that induces CYP enzymes to lower concentration of drugs.
Describe mechanism w/ example of smoking-drug interactions
Chemicals in smoke interact with antipsychotics, antidepressants, benzodiazepines, oral contraceptives, inhaled corticosteroids, beta blockers.
Smoking induces CYP activity.
E.g. smoking increases warfarin clearance and reduce effect.
Smoking increases ADR of COCs
Describe mechanism w/ examples of drug-food interactions
High fat meals slow down gastric emptying and delay drug absorption.
Calcium can form insoluble chelates to prevent absorption.
Grapefruit juice- CYP . increase bioavailability (diazepam, sildenafil, atorvastatin)
Describe MOSES approach
Evaluates drug interactions
M- mechanism (ADME)
O- outcome (what happens)
S- significance (major or minor)
E- evidence (case reports, theory vs well established)
S- strategy (what are you recommeding)
Enlist important questions to consider when evaluating drug interations
Previous credible reports of this interaction?
Observed interaction consistent with known properties?
Event consistent w/ interaction time course (onset/offset)?
