The effects of substituting frusemide for a thiazide diuretic in the drug regimens of patients with essential hypertension.

Eighteen patients with mild to moderate hypertension on a drug regimen which included a thiazide diuretic had the latter substituted by frusemide for twelve weeks after an initial two-week placebo wash-out period. Blood pressure and heart rate and a number of plasma and urinary biochemical indices were measured. Significant findings included a reduction in standing blood pressure and an elevation of plasma sodium, potassium, chloride, osmolarity, creatinine and alkaline phosphatase levels at the end of the twelve week frusemide phase relative to the values on the thiazide. However the means for all the biochemical indices remained within the normal laboratory reference limits. In the 24-hour urinary studies, no significant findings emerged, apart from an elevated calcium. The foregoing suggest that frusemide is an effective component of an anti-hypertensive drug regimen and that in a dose of 40 mg/day it produces no detectable perturbations of plasma electrolytes. The significance of the enhanced levels of urinary calcium excretion in conjunction with the augmented plasma alkaline phosphatase is unclear.