Calcium channel blockers--are they diuretics?

Seven untreated patients with essential hypertension but without target organ damage were admitted to hospital. Urine was collected the following day from 08.00 to 13.00 h, 13.00 to 18.00 h, and 18.00 to 08.00 h. The protocol was repeated the next day following 30 mg oral nicardipine. Intra-arterial blood pressure (IABP), plasma volume, and plasma renin activity (PRA) also were measured daily. Following the single-dose study, the patients were treated as outpatients and received oral nicardipine 20, 30, or 40 mg four times daily. They were readmitted 2 months later for further study, at which time the protocol was repeated. Urine output between 08.00 and 13.00 h significantly increased after the single- and multiple-dose studies. Following the single-dose study, this diuresis was associated with a natriuresis. Urine output increased over the 24 h following multiple-dose treatment, but this increase was not statistically significant. During the multiple-dose 24 h study, there was an increase in urinary potassium (P less than 0.05). Mean IABP was reduced significantly after the single- and multiple-dose studies (P less than 0.02 and less than 0.05, respectively). During the study, there were no significant changes in plasma volume, weight, or plasma renin activity.