Tiapamil and hydrochlorothiazide: a double-blind comparison of two antihypertensive agents

Tiapamil is an investigational calcium-channel antagonist that is chemically related to verapamil. The antihypertensive efficacies of tiapamil and hydrochlorothiazide (HCTZ) were compared in a randomized double-blind trial. Thirty patients, age 44 to 80 years, with mild to moderate hypertension (World Health Organization stage I-II) entered and completed the study. Previous therapy, if any, was stopped for at least one week prior to study initiation, and patients received placebo tablets for two weeks. The participants were then given active medication, which was titrated for the next three weeks; HCTZ 25 to 50 mg bid or tiapamil 300 to 600 mg bid was given until supine diastolic blood pressure (BP) was no higher than 90 mm Hg or the ceiling dose was reached. Both drugs caused a significant reduction in systolic as well as in diastolic blood pressure (P less than .01). The reduction was seen in both the supine and erect position. The median decrease in supine systolic blood pressure from baseline to the end of treatment was 20 mm Hg in the tiapamil group and 27 mm Hg in the hydrochlorothiazide group, whereas the median decrease in supine diastolic blood pressure was 14 mm Hg and 18 mm Hg, respectively. The median difference in supine diastolic BP reduction after HCTZ and tiapamil administration was 3.8 mm Hg (not significant). There were no significant changes in heart rate. Dizziness occurred in one patient taking tiapamil and in three receiving HCTZ. One patient receiving HCTZ developed acute arthritis urica.(ABSTRACT TRUNCATED AT 250 WORDS)