Azithromycin × Colchicine

Azithromycin inhibits the P-glycoprotein transporter less than clarithromycin but still blocks a colchicine clearance route. Colchicine plasma levels rise moderately; toxicity has been reported with prolonged combination, especially in older patients and chronic kidney disease.

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

For short azithromycin courses (3–5 days), no special measures are needed. In chronic kidney disease or hepatic impairment, temporarily halve the colchicine dose. For prolonged azithromycin therapy, switch antibiotic (doxycycline) or replace colchicine with allopurinol.