Chronic administration of verapamil, ketoconazole and carbamazepine: impact on immunological parameters.

Inhibitors of P-glycoprotein (P-gp) (verapamil) or cytochrome P-450 (ketoconazole) may reduce IL2 production and T lymphocyte proliferation in vitro. We have examined the effects of chronic oral administration of these drugs and of the cytochrome P450 inductor, carbamazepine, on the hematological and immunological parameters of mice. We found no changes after giving the mice 0.12 mg verapamil, 0.85 mg ketoconazole, or 0.514 mg carbamazepine per mouse for 4 weeks (5 days/week). But giving the drugs for an additional 7 weeks at 0.6 mg (verapamil), 4.25 mg (ketoconazole) or 2.57 mg/mouse (carbamazepine), resulted in significant decreases in monocytes in the verapamil treated group (−51%) and in CD4+ cells in the carbamazepine group (−35%). Chronic oral administration of these drugs reduced the lymphocyte counts of mice by 10–18% and their NK counts by 10–16%. These changes could be due to changes in P-gp function in the transport of IL2, with decreases caused by verapamil and ketoconazole.