FNP Pharmacology Cheat Sheet: Drug Classes & Uses

Traditional norethindrone progestin-only pills have a very narrow efficacy window and must be taken within a strict three-hour timeframe. Because she missed her dose by five hours, her cervical mucus will begin to thin, significantly reducing contraceptive efficacy. She must take the late pill immediately, resume her normal schedule, and use backup barrier contraception for the next 48 hours. Emergency contraception is not indicated because unprotected intercourse has not yet occurred. Taking two pills is the protocol for missed combined oral contraceptives, not progestin-only formulations.

Clarithromycin is a strong CYP3A4 inhibitor that drastically reduces the metabolism of simvastatin, leading to toxic statin levels and a high risk of rhabdomyolysis. Because of this severe interaction, the safest approach is to temporarily hold the statin (Option A). Reducing the dose by half (Option B) is insufficient because the interaction is profound and unpredictable. Monitoring liver function tests (Option C) does not prevent the acute muscle toxicity that is the primary concern. Separating the administration times (Option D) is ineffective because the inhibition of the CYP450 enzyme occurs at the hepatic level and lasts throughout the duration of the antibiotic therapy, regardless of when the daily doses are ingested.

Bupropion is contraindicated in patients with a history of eating disorders like bulimia nervosa due to a significantly lowered seizure threshold. Varenicline is a safe, effective oral alternative that does not carry this specific risk. Option A is incorrect because bupropion could provoke seizures in this patient, regardless of monitoring. Options C and D are incorrect; while nortriptyline and clonidine are second-line off-label options for smoking cessation, varenicline is an FDA-approved first-line agent with superior efficacy and should be prioritized over second-line therapies.