Drug Interaction Report

ADJUST DOSING INTERVAL: Oral products containing zinc such as mineral supplements and multivitamins may interfere with the gastrointestinal absorption of cephalexin, ceftibuten or cephradine. In one pharmacokinetic study (n=12), concurrent administration of zinc sulfate (250 mg, single oral dose) and cephalexin (500 mg, single oral dose) decreased cephalexin maximum concentration (Cmax) and systemic exposure (AUC; 0-inf) by 31.05% and 27.4%, respectively. However, in the same study, when zinc sulfate was administered 3 hours after the cephalexin dose, no significant alteration in cephalexin pharmacokinetics were observed.

MANAGEMENT: Oral medications or mineral supplements that contain zinc are recommended to be administered at least 3 hours after the cephalexin, ceftibuten or cephradine dose.

H2 antagonists may reduce the clearance of nicotine. Cimetidine, 600 mg given twice a day for two days, reduced clearance of an intravenous nicotine dose by 30%. Ranitidine, 300 mg given twice a day for two days, reduced clearance by 10%. The clinical significance of this interaction is not known. Patients should be monitored for increased nicotine effects when using the patches or gum for smoking cessation and dosage adjustments should be made as appropriate.