Urinary electrolyte excretion after frusemide, amiloride and a combination of these drugs: an open, crossover study.

Urinary volume and electrolyte excretion were monitored for 24 hours in 12 elderly, catheterized patients with mild congestive cardiac failure. Five timed collections (0 to 3, 3 to 6, 6 to 9, 9 to 12 and 12 to 24 hours) were made after single doses of 40 mg frusemide, 5 mg amiloride and a combination tablet containing both 40 mg frusemide and 5 mg amiloride. Patients received each therapy according to a Latin Square design, with a 6-day washout phase separating the three study periods. The study periods consisted of a 24-hour control urinary collection, immediately followed by diuretic and a further 24-hour urine collection. Diuretics were not administered immediately prior to the study or during the washout phases. Amiloride, as expected, showed mild diuretic and natriuretic properties, but in the 12 to 24-hour period it induced a greater diuresis (p less than 0.05) than did frusemide or the combination. Frusemide and the combination tablet both produced a rapid and powerful diuresis in the 0 to 3-hour post-dose period and did not differ significantly in urine output at any time point. However, a difference in natriuretic activity was seen between frusemide and the combination, with the latter producing a significantly greater sodium excretion in the 12 to 24-hour period (p less than 0.05). Potassium-retaining activity throughout the 24 hours was marked after amiloride, with potassium excretion being significantly less (p less than 0.05) than either control, frusemide or the combination.(ABSTRACT TRUNCATED AT 250 WORDS)