Atorvastatin × Clarithromycin

Atorvastatin clearance depends on hepatic CYP3A4, but unlike simvastatin only ~70% of the dose follows this route – the rest uses alternative pathways. Clarithromycin strongly inhibits CYP3A4. Atorvastatin plasma levels rise 4- to 5-fold. The exposure increase is smaller than with simvastatin but still clinically significant for muscle injury risk.

Pain and weakness in large muscle groups, dark urine. Laboratory: elevated creatine kinase. Symptoms appear 3–7 days into concurrent therapy. Acute rhabdomyolysis is less common than the clarithromycin + simvastatin pair but has been reported.

Hold atorvastatin for the clarithromycin course or switch the patient to pravastatin or rosuvastatin. If statin therapy cannot be paused, replace the antibiotic: azithromycin (minimal CYP3A4 interaction) or a non-macrolide class based on susceptibility.