The influence of captopril on the diuretic effect of furosemide was investigated in fluid-intake controlled 8 healthy subjects.
Furosemide (20mg) was injected intravenously and urine samples for sodium and furosemide were collected over a 60-min period. Plasma samples for plasma renin activity (PRA) and angiotensin II (AII) were obtained just before and 60min after furosemide administration. Blood pressure (BP) was also determined just before and 60 min after the drug. A second-study was carried out one week after the first-study. On this occasion, the subjects were pretreated with captopril (50mg) and the protocol of the first-study was repeated.
No significant difference was observed in urine volume, urinary sodium or furosemide excretion between the two studies. Although PRA increased after furosemide with captopril, AII did not elevate. BP did not change significantly after furosemide with or without captopril.
These results indicate that the diuretic effects of furosemide might not be influenced by captopril.