Nisoldipine

Drug Interactions A 30 to 45% increase in AUC and C max of nisoldipine was observed with concomitant administration of cimetidine 400 mg twice daily. Ranitidine 150 mg twice daily did not interact significantly with nisoldipine (AUC was decreased by 15 - 20%). No pharmacodynamic effects of either histamine H 2 receptor antagonist were observed. CYP3A4 inhibitors and inducers : SULAR is substrate of CYP3A4 and coadministration of SULAR with any known inducer or inhibitor of CYP3A4 should be avoided in general. Coadministration of phenytoin with a dose bioequivalent to 34 mg SULAR tablets in epileptic patients lowered the nisoldipine plasma concentrations to undetectable levels.

Coadministration of SULAR with phenytoin should be avoided and alternative antihypertensive therapy should be considered. Pharmacokinetic interactions between nisoldipine and beta-blockers (atenolol, propranolol) were variable and not significant. Propranolol attenuated the heart rate increase following administration of immediate release nisoldipine. The blood pressure effect of SULAR tended to be greater in patients on atenolol than in patients on no other antihypertensive therapy. Quinidine at 648 mg bid decreased the bioavailability (AUC) of nisoldipine by 26%, but not the peak concentration. Immediate release nisoldipine increased plasma quinidine concentrations by about 20%.

This interaction was not accompanied by ECG changes and its clinical significance is not known. No significant interactions were found between nisoldipine and warfarin or digoxin.

Pregnancy Nisoldipine was neither teratogenic nor fetotoxic at doses that were not maternally toxic. Nisoldipine was fetotoxic but not teratogenic in rats and rabbits at doses resulting in maternal toxicity (reduced maternal body weight gain). In pregnant rats, increased fetal resorption (postimplantation loss) was observed at 100 mg/kg/day and decreased fetal weight was observed at both 30 and 100 mg/kg/day. These doses are, respectively, about 5 and 16 times the MRHD when compared on a mg/m 2 basis. In pregnant rabbits, decreased fetal and placental weights were observed at a dose of 30 mg/kg/day, about 10 times the MRHD when compared on a mg/m 2 basis.

In a study in which pregnant monkeys (both treated and control) had high rates of abortion and mortality, the only surviving fetus from a group exposed to a maternal dose of 100 mg nisoldipine/kg/day (about 30 times the MRHD when compared on a mg/m 2 basis) presented with forelimb and vertebral abnormalities not previously seen in control monkeys of the same strain. There are no adequate and well controlled studies in pregnant women. SULAR should be used in pregnancy only if the potential benefit justifies the potential risk to the fetus.

Nursing Mothers It is not known whether nisoldipine is excreted in human milk. Because many drugs are excreted in human milk, a decision should be made to discontinue nursing, or to discontinue SULAR, taking into account the importance of the drug to the mother.