Azithromycin × Colchicine

Colchicine is cleared with the help of the P-glycoprotein transporter and the CYP3A4 enzyme (colchicine SmPC). Azithromycin inhibits P-glycoprotein and increases colchicine exposure: the area under the curve (AUC) rises by 57% and the peak concentration by 22% (azithromycin SmPC). Colchicine has a narrow therapeutic index and azithromycin has a long half-life, so its effect persists after the course ends (azithromycin SmPC).

Profuse diarrhoea, vomiting, abdominal pain as first signs. With prolonged combination, muscle weakness, peripheral neuropathy, and pancytopenia follow.

Monitor the patient clinically during the azithromycin course and after it ends (azithromycin SmPC) and, where possible, check colchicine blood concentrations (colchicine SmPC). Azithromycin inhibits P-glycoprotein, and in renal or hepatic impairment colchicine should not be combined with such drugs whenever possible; if colchicine is continued, reduce its dose substantially and monitor the patient closely (colchicine SmPC). Colchicine itself is contraindicated in severe renal or hepatic impairment (colchicine SmPC). In older patients and in renal impairment, the total colchicine dose over a 4-day gout attack should not exceed 3 mg (colchicine SmPC). At the first sign of nausea, vomiting, abdominal pain or diarrhoea, stop colchicine; the patient needs urgent care (colchicine SmPC).