colchicine and clarithromycin

Clarithromycin inhibits CYP3A4 and P-glycoprotein, both of which are involved in the metabolism and efflux transport of colchicine. This inhibition significantly increases colchicine plasma concentrations, leading to a higher risk of toxicity.

Elevated colchicine levels can cause gastrointestinal symptoms (diarrhoea, nausea, vomiting), muscle weakness, rhabdomyolysis, bone marrow suppression, and potentially fatal multi-organ failure. Patients with renal or hepatic impairment are at particular risk.

Avoid co-prescription whenever possible, especially in patients with renal or hepatic impairment. If a macrolide is needed, consider azithromycin, which does not significantly inhibit CYP3A4. If co-administration is unavoidable in a patient with normal renal and hepatic function, reduce the colchicine dose (e.g., to 0.6 mg once daily) and monitor closely for signs of toxicity, including blood counts and renal function.

Well-established interaction with multiple case reports, pharmacokinetic studies, and regulatory warnings supporting the increased risk of colchicine toxicity when co-administered with clarithromycin.