A hospital pharmacovigilance committee is reviewing a series of adverse drug events and therapeutic failures. Match each clinical presentation (left) with the underlying pharmacokinetic or pharmacodynamic mechanism most likely responsible for the outcome (right).
- Initiation of amiodarone for atrial fibrillation leads to the development of nausea, xanthopsia, and atrioventricular block in a patient previously stable on digoxin.Inhibition of intestinal and renal P-glycoprotein efflux transporters
- An unintended pregnancy occurs in a patient strictly adherent to combined oral contraceptives who recently completed a multidrug regimen for active pulmonary tuberculosis.Upregulation of hepatic cytochrome P450 3A4 transcription
- Escalating doses of extended-release oxycodone are required over a six-month period to maintain baseline analgesia in a patient with severe chronic radiculopathy.Internalization and uncoupling of G-protein coupled receptors
- Development of coarse tremors, ataxia, and confusion occurs shortly after adding chlorthalidone to the regimen of a patient with well-controlled bipolar disorder on lithium.Enhanced compensatory reabsorption of monovalent cations in the proximal tubule
Cevap
Digoxin toxicity is caused by P-glycoprotein inhibition; contraceptive failure is caused by CYP3A4 induction; opioid tolerance is caused by receptor uncoupling/internalization; and lithium toxicity is caused by enhanced proximal tubule reabsorption.
Each clinical scenario corresponds to a distinct pharmacological principle. The amiodarone-digoxin interaction is a classic example of P-glycoprotein inhibition. The rifampin-oral contraceptive interaction demonstrates CYP3A4 induction, accelerating drug clearance and leading to subtherapeutic levels. Opioid tolerance exemplifies a pharmacodynamic shift at the cellular level via receptor downregulation. Finally, the thiazide-lithium interaction highlights altered renal pharmacokinetics, where induced volume depletion enhances proximal tubular reabsorption of lithium.
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Anahtar Kavram
Understanding specific drug interactions mediated by transport proteins (P-gp), metabolizing enzymes (CYP450), renal clearance mechanisms, and receptor-level pharmacodynamics is essential for preventing adverse outcomes.