Clarithromycin × Colchicine

Colchicine is cleared via hepatic CYP3A4 and the P-glycoprotein transporter. Clarithromycin inhibits both. Colchicine plasma levels rise several-fold. The narrow therapeutic window makes any increase clinically dangerous. FDA Colcrys carries a boxed warning for fatal toxicity.

Profuse diarrhoea, vomiting, abdominal pain – first signs of toxicity. Pancytopenia (drop in leukocytes, erythrocytes, platelets), muscle weakness, peripheral neuropathy, hepatic and renal injury follow. Fatal cases have been reported.

For patients with renal impairment (creatinine clearance below 60 mL/min) or hepatic impairment, the combination is not prescribed. With preserved renal and hepatic function, use colchicine 0.3 mg every other day, no more than 5 days. Alternative antibiotic: azithromycin (minimal interaction).