Bumetanide-induced rise in plasma renin activity.

Abstract

The effect of bumetanide on renal function, plasma renin activity (PRA), and electrolyte excretion was investigated in seven normal men who had been on a daily diet containing 120 mEq sodium and 80 mEq potassium for three days. A single oral dose of 2 mg bumetanide induced substantial diuresis and variable but significant increases in PRA. Diuresis occurred promptly, reached a peak at 1 to 2 hr, and abated almost completely at 6 hr. The PRA increase began at 1 hr but, unlike the diuretic effect, it persisted for up to 12 hr. Peak effects occurred between 4 to 12 hr. The initial rise in PRA during early diuresis was associated with a significant increase in creatinine clearance, but further rises in PRA during later diuresis were accompanied by a fall in creatinine clearance. At maximal diuresis, sodium excretion increased 16‐fold while potassium excretion tripled. Chloride excretion, which increased 20‐fold, represented the largest increase in electrolyte excretion. Plasma levels of bumetanide measured by radioimmunoassay were detected as early as 30 min and peak concentrations were noted at 1 hr. Levels declined thereafter with a mean half‐life of 2.0 hr. The hourly excretion of bumetanide in the urine was greatest at 1 to 2 hr and correlated with sodium excretion (r = 0.94, p < 0.001).