A Comparison of the Safety of Therapeutically Equivalent Doses of Isradipine and Diltiazem for Treatment of Essential Hypertension: An Alternative Viewpoint

We compared the safety of a new dihydropyridine calcium entry blocker, isradipine, with an equipotent dose of diltiazem in 174 mild hypertensives (diastolic blood pressure [DBP] 95 to 105 mm Hg). After appropriate washout and placebo periods, patients were randomly assigned to receive either 1.25 mg isradipine twice daily (Group I) or 40 mg diltiazem thrice daily (Group D). If DBP remained above 90 mm Hg, doses were increased to a maximum of 5 mg isradipine twice daily or 120 mg diltiazem thrice daily. Active therapy was given for a total of 12 weeks. Only 18 patients (nine from each group) did not complete the protocol. The patients were well-matched at baseline with a mean BP of 149/100 mm Hg for those who were randomized to isradipine and completed the protocol and 153/99 mm Hg for the diltiazem group. The responses to each drug were excellent with 72% of the isradipine patients and 73% of the diltiazem group having DBP less than 90 mm Hg at the completion of the study. Of the 156 patients who completed the protocol, only 18 patients (ten in Group I and eight in Group D) failed to respond. Both drugs were well-tolerated. No adverse reactions were reported by 68 percent of the patients in Group I and 65% of those in Group D. The most common side effect was headache (9.0% in Group I and 7.8% in Group D) followed by fatigue (5.2% in Group I and 3.9% in Group D). Age and race did not predict response to either agent but men responded slightly better to diltiazem than women. We conclude that isradipine and diltiazem are equally well tolerated and can be used successfully as a monotherapy to treat hypertension in a wide variety of patients.