Colchicineinteractions

Colchicine is a substrate of the efflux transporter P-glycoprotein (P-gp), and the CYP3A4 metabolizing enzyme. Fatal drug interactions have been reported when colchicine is administered with clarithromycin, a dual inhibitor of CYP3A4 and P-glycoprotein. Toxicities have also been reported when colchicine is administered with inhibitors of CYP3A4 that may not be potent inhibitors of P-gp (e.g., grapefruit juice, erythromycin, verapamil), or inhibitors of P-gp that may not be potent inhibitors of CYP3A4 (e.g., cyclosporine). Patients with renal or hepatic impairment should not be given colchicine capsules with drugs that inhibit both P­glycoprotein and CYP3A4. Combining these dual inhibitors with colchicine capsules in patients with renal and hepatic impairment has resulted in life-threatening or fatal colchicine toxicity. Physicians should ensure that patients are suitable candidates for treatment with colchicine capsules and remain alert for signs and symptoms of toxic reactions associated with increased colchicine exposure due to drug interactions. Signs and symptoms of colchicine toxicity should be evaluated promptly and, if toxicity is suspected, colchicine capsules should be discontinued immediately. Co-administration of P-gp or CYP3A4 inhibitors or inhibitors of both P-gp and CYP3A4 (e.g., clarithromycin or cyclosporine) have been reported to lead to colchicine toxicity. The potential for drug-drug interactions must be considered prior to and during therapy. Concomitant use of colchicine capsules and inhibitors of CYP3A4 or P-gp should be avoided if possible. If co-administration of colchicine capsules and an inhibitor of CYP3A4 or P-gp is necessary, the dose of colchicine capsules should be reduced and the patient should be monitored carefully for colchicine toxicity. 7.1 CYP3A4 The concomitant use of colchicine capsules and CYP3A4 inhibitors (e.g., clarithromycin, ketoconazole, grapefruit juice, erythromycin, verapamil, etc.) should be avoided due to the potential for serious and life-threatening toxicity. If co-administration of colchicine capsules and a CYP3A4 inhibitor is necessary, the dose of colchicine capsules should be adjusted by either reducing the daily dose or reducing the dose frequency, and the patient should be monitored carefully for colchicine toxicity.

7.2 P-glycoprotein

The concomitant use of colchicine capsules and inhibitors of P-glycoprotein (e.g. clarithromycin, ketoconazole, cyclosporine, etc.) should be avoided due to the potential for serious and life-threatening toxicity. If co-administration of colchicine capsules and a P-gp inhibitor is necessary, the dose of colchicine capsules should be adjusted by either reducing the daily dose or reducing the dose frequency, and the patient should be monitored carefully for colchicine toxicity.

7.3 HMG-CoA

Reductase Inhibitors and Fibrates Some drugs such as HMG-CoA reductase inhibitors and fibrates may increase the risk of myopathy when combined with colchicine capsules. Complaints of muscle pain or weakness could be an indication to check serum creatinine kinase levels for signs of myopathy.

7.4 Drug-Drug

Interaction Studies Four pharmacokinetic studies evaluated the effects of co-administration of voriconazole (200 mg BID), fluconazole (200 mg QD), cimetidine (800 mg BID), and propafenone (225 mg BID) on systemic levels of colchicine. Colchicine can be administered with these drugs at the tested doses without a need for dose adjustment. However, these results should not be extrapolated to other co-administered drugs.