In a randomized double-blind parallel group study the effects of two formulations of
piretanide (standard
tablet and slow-release
capsule) were compared in patients with mild to moderate
essential hypertension. Forty patients entered the study and thirty-seven completed it. Both formulations of
piretanide produced a significant reduction in erect and supine blood pressure which was evident at 2 weeks and was maintained and further enhanced over the ensuing trial period. A mean maximal fall in supine diastolic pressure of 22% was observed in the
piretanide tablet group, and of 20% in the slow-release
piretanide group. Blood pressure fell more quickly at the beginning of treatment with the
tablet preparation, such that there was a significant difference between the groups up to the fourth week. After this point the blood pressure lowering effect was very similar in both groups and there was a progressive reduction in supine blood pressures over the 12-week active-treatment period. Slow-release
piretanide produced a smoother effect than the
tablet formulation. There were no significant changes in serum
potassium and serum
magnesium in either treatment group. Minor changes were seen in some other biochemical and haematological variables but these were of no clinical significance. Three patients were withdrawn from the study because of side-effects: one because of an excessive
antihypertensive response to the
tablet formulation; and two because of
allergic reactions to the slow-release preparation. Side-effects were otherwise mild and infrequent.