A 40-year-old man has been taking fluoxetine (Prozac) for seasonal depression for the past 3 months, as prescribed by his psychiatric-mental health nurse practitioner. He believes his symptoms are well controlled. The patient's primary care provider recently prescribed atorvastatin (Lipitor) for hypercholesterolemia. Today, he complains of muscle and joint pain. The PMHNP suspects possible rhabdomyolysis. Which answer choice describes the reason for this?

Choice A reason: While rhabdomyolysis is a known rare adverse effect of atorvastatin, the risk increases significantly when atorvastatin interacts with other drugs that inhibit its metabolism. This answer is partially correct but does not explain the mechanism. Choice B reason: Fluoxetine is not commonly associated with rhabdomyolysis as a direct side effect. Its role in this case is more likely due to drug-drug interaction rather than intrinsic toxicity. Choice C reason: Fluoxetine is not a CYP450 3A4 inducer. This choice is incorrect because it misrepresents fluoxetine’s pharmacologic profile. Choice D reason: Fluoxetine is a known inhibitor of CYP450 3A4. Atorvastatin is metabolized by this enzyme. Inhibition of CYP3A4 by fluoxetine can lead to increased plasma levels of atorvastatin, raising the risk of statin-induced rhabdomyolysis due to impaired clearance.