Efficacy and safety of the 200–300 mg sustained release formulation of diltiazem administered once daily in patients with stable angina

The aim of this multicentre randomised double blind study was to compare the efficacy and safety of the 200–300 mg sustained release diltiazem formulation administered once daily (200–300 SR) with standard diltiazem (D) given three or four times daily to patients with stable angina. Patients aged 59 years, with a reproducible exercise test on placebo, were randomised to 4 weeks of treatment with 200–300 SR (n=70) or D (n=74). The initial dosage was 200 mg in the 200–300 SR group and 60 mg t.i.d. in the D group, increased to 300 mg once daily or 60 mg q.i.d., respectively, if ergometric parameters, which were always measured at the end of the dosing period, had not improved after two weeks. After 4 weeks of treatment, the antianginal efficacy at rest was comparable in the 200–300 SR and the D group; there was a prolongation of the total duration of exertion of 14% and 18% respectively (P<0.01 vs placebo for both groups with no intergroup difference). A dose-effect relation was found with both formulations.The 200–300 SR formulation gave full 24 hour anti-ischaemic protection when administered once daily. Its efficacy and safety were comparable to those of standard diltiazem t.i.d. or q.i.d. in patients with stable angina. The once daily administration should improve treatment compliance.