The
plasma levels of
diltiazem,
nifedipine, nilvadipine,
verapamil and possibly those of barnidipine,
isradipine, lercanidipine, manidipine, nicardipine,
nimodipine, and
nisoldipine are markedly reduced by
rifampicin. They may become therapeutically ineffective unless their dosages are raised.
Increase the frequency of blood pressure monitoring and adjust the antihyperten- sive dose, or use an alternative drug, as necessary. Note that the manufacturers of
nifedipine and
nisoldipine contraindicate their use with rifampicin, and the manufacturer of
nimodipine advises against the combination.