Cardivasc Drug Interactions

Antibacterials: The macrolide antibacterials are inhibitors of the cytochrome P450 isoenzyme CYP3A4 and may inhibit the metabolism of calcium-channel blockers like amlodipine.
Antiepileptics: The effects of dihydropyridine calcium-channel blockers (e.g. amlodipine) may be reduced by enzyme-inducing antiepileptics such as carbamazepine, phenobarbital, and phenytoin.
Antifungals: Azole antifungals inhibit cytochrome P450 enzyme system and may therefore interfere with metabolism of calcium-channel blockers (e.g. amlodipine).
Antivirals: The HIV-protease inhibitors are known to inhibit the cytochrome P450 isoenzyme CYP3A4 and may therefore interfere with the metabolism of calcium-channel blockers (e.g. amlodipine).
Digoxin: The mechanism of interaction between calcium-channel blockers and digoxin is not completely understood but appears to be related to decreased renal and nonrenal clearance of digoxin. The pharmacodynamic effects of digoxin and calcium-channel blockers (e.g. amlodipine) may also be additive.
Grapefruit juice: Grapefruit juice inhibits the cytochrome P450 isoenzyme CYP3A4, particularly in the intestinal wall, and has shown to increase markedly the bioavailability of orally-administered calcium-channel blockers.
The interaction may be less significant with amlodipine that have a higher bioavailability.
Immunosuppressants: Ciclosporin concentrations have been reported to increase or to remain unchanged with amlodipine. Use of amlodipine with ciclosporin may exacerbate the problem of gingival hyperplasia.
Beta-adrenergic blockers: Beta-adrenergic blockers have additive effects and must be used with caution to prevent excessive myocardium depression.
Antihypertensive drugs: Antihypertensive drugs such as prazosin, methyldopa, clonidine have additive effects and can cause dangerous hypotensive effects.
Non-depolarizing muscle relaxants: Action may be increased.
Cimetidine: decreases the first pass effects of calcium channel blockers.