Dose-effect and concentration-effect relationships of pinacidil and hydrochlorothiazide in hypertension.

To determine dose-effect and concentration-effect relationships in hypertension for pinacidil and hydrochlorothiazide when given alone and together, we conducted a randomized, double-blind, 4 X 3 factorial, modified fixed-dose multicenter trial. Three hundred and eighty-four patients with essential hypertension (supine diastolic blood pressure, 95 to 110 mm Hg) were assigned to one of 12 groups that received all combinations of four doses of pinacidil (0, 12.5, 25, and 37.5 mg, b.i.d.) with three doses of hydrochlorothiazide (0, 12.5, and 25 mg, b.i.d.). Significant dose- and concentration-effect relationships were seen for pinacidil and hydrochlorothiazide on diastolic blood pressure. For pinacidil, dose- and concentration-effect relationships were steeper after the dose than before the dose. A significant interaction with hydrochlorothiazide was noted such that, when combined with 12.5 mg hydrochlorothiazide, 12.5 mg pinacidil had near-maximal effects on blood pressure at both peak and trough. Edema occurred in 47% of those who received 37.5 mg pinacidil monotherapy (19% discontinued). The administration of 12.5 mg pinacidil with 12.5 mg hydrochlorothiazide appears to be optimal for efficacy and safety.