Plendil Drug Interactions

Felodipine is metabolised in the liver by cytochrome P450 3A4 (CYP3A4). Concomitant administration of substances which interfere with the CYP3A4 enzyme system may affect plasma concentrations of felodipine.
CP3A4 inducers: Drugs that increase the metabolism of felodipine by induction of P450 are, for example, carbamazepine, phenytoin, phenobarbital and rifampicin, as well as St. John's wort (Hypericum perforatum). When Plendil was administered together with carbamazepine, phenytoin and phenobarbital, the AUC of felodipine was reduced by 93% and C_max by 82%. Combination with CYP3A4 inducers should be avoided.
CYP3A4 inhibitors: Drugs that are potent CYP3A4 inhibitors are for example, azole antimycotics (itraconazole, ketoconazole), macrolide antibiotics (erythromycin) and HIV protease inhibitors. Concomitant administration of itraconazole resulted in eight-fold increases of the C_max of felodipine and six-fold increases of the AUC. Concomitant administration of erythromycin led to approximately 2.5-fold increases of the C_max and the AUC of felodipine. Combination with potent CYP3A4 inhibitors should be avoided.
Grapefruit juice inhibits CYP3A4. Administration of felodipine together with grapefruit juice resulted in approximately two-fold increases of the C_max and the AUC of felodipine. Combination with grapefruit juice should be avoided.
Tacrolimus: Felodipine may increase the concentration of tacrolimus. When used together, the concentration in serum of tacrolimus should be monitored and the tacrolimus dose may need to be adjusted.
Cyclosporin: Concomitant treatment with cyclosporin and felodipine increased the plasma concentration of felodipine by 150% and the AUC by 60%. The effect of felodipine on the pharmacokinetics of cyclosporin is, however, limited.
Cimetidine: Concomitant treatment with cimetidine and felodipine increased the C_max and AUC of felodipine by approximately 55%.