Aims: To investigate the dose-response relationship and contribution of verapamil SR and trandolapril given in combination once a day for the treatment of essential hypertension.
Methods: A randomized, double-blind, placebo controlled, factorial, 12 arm parallel group comparison with placebo, verapamil SR (120, 180 mg), trandolapril (0.5, 1.0, 2.0 mg) covering all combinations of both drugs. A 4 week placebo run-in period followed by 6 weeks of treatment. Four hundred and fifty-six patients from office practice (22 centres) with mild to moderate hypertension enrolled and 426 with diastolic pressure > or = 100 mm Hg at the end of run-in period were randomized. Main outcome measures were reduction in sitting systolic (SBP) and sitting diastolic (DBP) blood pressure.
Results: The combination of verapamil SR and trandolapril, particularly verapamil SR 180 mg and trandolapril 0.5 or 1.0 mg was significantly superior to both monocomponents at the same dose (P<0.05). For these combinations, the adjusted mean reductions in DBP from baseline to last visit were 14.1 and 16.0 mm Hg, respectively. Response surface analysis provided further evidence that these combinations were optimal for antihypertensive efficacy. All treatments were well tolerated. The incidence of adverse events did not differ significantly between treatment groups; the profile of adverse events on combination therapy was mild and consistent with that of each monocomponent.
Conclusions: All dosage combinations of verapamil SR and trandolapril produced significantly greater reduction of blood pressure than the monotherapy at the same dosage. However, verapamil SR 180 mg in combination with trandolapril 1.0 mg was the dosage with the greatest blood pressure reduction and had the greatest effects compared with the monocomponents.