Grapefruit juice very markedly increases the bioavailability of
felodipine and
nisoldipine, and alters their haemodynamic effects. The bioavailability of nicardipine,
nifedipine,
nimodipine or nitrendipine is increased without significantly altering haemodynamic effects, whereas the bioavailability of
amlodipine,
diltiazem and
verapamil is only minimally affected. However, with
verapamil some ECG changes were seen.
The manufacturers of
felodipine say that it should not be taken with
grapefruit juice. It has been suggested that whole grapefruit or products made from grapefruit
peel such as marmalade should also be avoided in patients taking
felodipine. The manufacturers of lercanidipine,
nifedipine,
nimodipine,
nisoldipine and verapa- mil also contraindicate
grapefruit juice, although this interaction is normally of little relevance with most
calcium-channel blockers in the majority of patients.