atorvastatin and clarithromycin

Clarithromycin is a potent inhibitor of CYP3A4, the enzyme primarily responsible for atorvastatin metabolism. This inhibition reduces atorvastatin clearance and significantly raises its plasma concentrations. Clarithromycin may also inhibit the OATP1B1 hepatic transporter, further increasing systemic exposure to atorvastatin.

Elevated atorvastatin levels increase the risk of dose-dependent muscle toxicity, including myopathy and rhabdomyolysis, which can be life-threatening. Symptoms include muscle pain, tenderness, weakness, and dark urine; creatine kinase may be markedly elevated.

Avoid co-prescribing atorvastatin with clarithromycin where alternatives exist. If concurrent use is necessary, use the lowest effective atorvastatin dose (e.g., 10 to 20 mg daily) and monitor for muscle symptoms and creatine kinase levels regularly. Consider temporary suspension of atorvastatin during clarithromycin therapy if possible.

Well established by pharmacokinetic studies and clinical case reports. Guidelines from major drug regulatory bodies recommend caution and dose adjustment.