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.
Interactions leading to increased plasma concentration of felodipine.
Enzyme inhibitors of the cytochrome P450 3A4 system have been shown to cause an increase in felodipine plasma concentrations.
Examples: Cimetidine; erythromycin; itraconazole; ketoconazole; certain flavonoids present in grapefruit juice.
Interactions leading to decreased plasma concentration of felodipine.
Enzyme inducers of the cytochrome P450 3A4 system may cause a decrease in plasma concentrations of felodipine.
Examples: Phenytoin; carbamazepine; rifampicin; barbiturates; Hypericum perforatum (Saint John's wort).
Felodipine may increase the concentration of tacrolimus. When used together, the tacrolimus serum concentration should be monitored and the tacrolimus dose may need to be adjusted.
Felodipine does not affect plasma concentrations of cyclosporin.