Drug Interactions and Adverse Drug Reactions Flashcards
6 cards from real PEBC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Drug Interactions and Adverse Drug Reactions flashcards as text
A patient on warfarin begins taking clarithromycin for a respiratory infection. Which mechanism best explains the increased bleeding risk?
Answer: Clarithromycin inhibits CYP3A4 and CYP2C9, reducing warfarin metabolism and increasing its plasma levels
Clarithromycin is a potent inhibitor of CYP3A4 and also inhibits CYP2C9, which metabolizes warfarin. Inhibition of these enzymes reduces warfarin clearance, elevating INR and increasing hemorrhage risk. INR should be monitored closely.
Which combination represents a potentially life-threatening pharmacodynamic drug interaction requiring strict avoidance?
Answer: Serotonergic antidepressant (SSRI) and tramadol
Combining an SSRI with tramadol (which also inhibits serotonin reuptake and is a weak serotonin agonist) can precipitate serotonin syndrome — a potentially fatal drug reaction characterized by hyperthermia, neuromuscular abnormalities, and autonomic instability.
A patient taking a monoamine oxidase inhibitor (MAOI) for depression consumes a meal rich in tyramine (e.g., aged cheese, cured meats). What adverse reaction is most likely?
Answer: Hypertensive crisis due to uninhibited tyramine-induced norepinephrine release
MAOIs inhibit monoamine oxidase in the gut and liver that normally degrades tyramine. When tyramine is absorbed intact, it triggers massive norepinephrine release from sympathetic nerve terminals, causing potentially fatal hypertensive crisis — the classic MAO-tyramine food interaction.
Which of the following is a Type A (augmented) adverse drug reaction?
Answer: Bradycardia and hypotension from an excessive dose of metoprolol
Type A adverse drug reactions are dose-dependent, predictable extensions of the drug's known pharmacological effect. Bradycardia from beta-blocker overdose is a predictable, dose-related ADR. Types B (bizarre) reactions like anaphylaxis and SJS are idiosyncratic and not related to normal pharmacology.
A patient is started on simvastatin 80 mg and also takes gemfibrozil for hypertriglyceridemia. Which serious drug interaction risk should prompt the pharmacist to intervene?
Answer: Increased risk of myopathy and rhabdomyolysis due to elevated simvastatin plasma concentrations
Gemfibrozil inhibits OATP1B1 and CYP2C8, significantly increasing simvastatin plasma concentrations and dramatically raising the risk of myopathy and rhabdomyolysis. This combination is generally contraindicated; if a fibrate is needed, fenofibrate is preferred over gemfibrozil with statins.
The Naranjo Adverse Drug Reaction Probability Scale is used in pharmacy practice for which primary purpose?
Answer: Assessing the probability that an observed adverse event is causally related to a specific drug
The Naranjo Scale is a standardized questionnaire (10 items) used to estimate the likelihood that an adverse clinical event is caused by a specific drug. It scores responses to generate a probability category: definite, probable, possible, or doubtful — essential for pharmacovigilance and ADR reporting.