Once daily compared with twice daily administration of slow-release diltiazem as monotherapy for hypertension.

We compared the efficacy of the antihypertensive drug diltiazem in a slow release formulation administered once daily with its twice daily administration as monotherapy in 34 patients with mild to moderate essential hypertension. All subjects received placebo for three weeks before the randomised, double blind, crossover study, and their supine diastolic blood pressure (BP) ranged from 95 mmHg to 115 mmHg. After the patients had received the placebo for three weeks diltiazem was titrated in the open label treatment to either 120 mg or 180 mg twice daily until the target BP level was achieved. After the open three weeks' of treatment with diltiazem twice daily patients were allocated randomly for either once daily or twice daily administration. After a six week, double blind period, the treatment was changed according to the crossover design. With a dose of 120 mg or 180 mg twice daily patients' supine and standing BP readings were significantly lower than when they took the drug once daily. In the subgroup (n = 19) with the maximum dose of diltiazem given twice daily and once daily BP levels were lower in those subjects on twice daily treatment than in those treated once a day with the same total daily dose, the differences being significant. Administration of diltiazem once a day in a slow release formulation was not as effective as a twice daily dose when the dose titration was greatest or when compared with the same dosage (240 mg x 1/day or 120 mg x 2/day).