This study compares the loop diuretic piretanide 6 mg in a slow-release formulation (PIR) with hydrochlorothiazide 25 mg (HCT) and the fixed combination altizide 15 mg-spironolactone 25 mg (ALT-SP) in hypertension. 1105 mild to moderate hypertensive patients entered a three-week placebo wash-out period; 899 were randomized in a 6-month, double-blind, parallel group treatment phase; 800 completed the study. Primary end-points; serum potassium concentration and quality of life at one month; secondary end-points: ionic, renal and metabolic variables; blood pressure (BP) measurements. HCT and ALT-SP were compared only to PIR using Dunnett's or chi 2 tests.
Results: No difference was found for the overall quality of life. No change of serum potassium concentration at one month was found in PIR while small decreases were detected with ALT-SP (-0.1 mM) and HCT (-0.26 mM). Serum creatinine concentration increased significantly in ALT-SP when compared to PIR. All the drugs were effective in reducing BP: HCT had a higher rate of responders than PIR with similar mean BP falls and ALT-SP induced greater falls in blood pressure.
Conclusion: PIR proves to be a potent antihypertensive drug without significant effect on serum electrolytes, plasma glucose and lipids. HCT was slightly more potent but induced a fall in serum potassium concentration with a significant risk of hypokalaemia. The addition of SP to ALT led to a more potent diuretic with a higher level of serum potassium and plasma creatinine disturbances.