Sustained-release and instant-release verapamil in treatment of angina pectoris.

The efficacy of a sustained-release preparation of verapamil (verapamil-SR) has been compared with that of a conventional instant-release formulation (verapamil-IR) in 10 patients with stable angina pectoris treated for 3 weeks with both preparations. The diurnal serum concentrations of verapamil and norverapamil did not differ significantly during treatment with verapamil-IR 120 mg t.i.d. and verapamil-SR 360 mg once daily, but verapamil-SR 240 mg produced significantly lower serum concentrations. The differences did not affect the exercise capacity or the occurrence of ST-segment depression during maximal exercise. Verapamil-SR was well tolerated. A multiple instant-release dosage regime can now be replaced by once daily administration of the sustained-release preparation.