Major
carvedilol × Colchicine
Alpha and beta blocker (non-selective β + α1)×Antigout agents
Mechanism
Carvedilol is a moderate P-glycoprotein inhibitor; colchicine is a P-glycoprotein substrate with a narrow therapeutic window. Colchicine plasma levels rise; myelosuppression and neuromyopathy risk.
Symptoms
Profuse diarrhoea, vomiting, abdominal pain. With prolonged combination: muscle weakness, peripheral neuropathy, falling leukocytes and platelets.
Management
In chronic kidney disease or hepatic impairment, the combination is not prescribed. With preserved function, colchicine 0.3 mg every other day for no more than 5 days. Alternative for gout: intra-articular glucocorticoid.