It is commonly assumed that
thiazide diuretics are ineffective in patients with advanced
renal failure (GFR < 30 ml/min/1.73 m2).
Thiazides act on the nephron segment distal to the ascending thick loop of Henle, that is, the site of action of
loop diuretics. Blockade of
sodium reabsorption in the
thiazide-sensitive segment should therefore obliterate the compensatory increase in
sodium reabsorption seen after administration of
loop diuretics and thus potentiate the natriuretic efficacy of
loop diuretics even in advanced
renal failure. In a single-blind, randomized, placebo controlled crossover study we compared the natriuretic and chloruretic effect of the
loop diuretic,
torasemide, given alone or in combination with the
thiazide diuretic, butizid, in 10 patients with advanced
renal failure (mean CIn 13.1 +/- 5.9 ml/min/1.73 m2). For two weeks patients adhered to a diet containing a standardized amount of Na+ and K+. On the 6th and 13th study days, two
sham infusions were given to patients in order to assess basal 24-hour urinary
electrolyte excretion. On the 7th and 14th days they were randomly allocated to receive either 50 mg i.v.
torasemide in combination with a
sham infusion or
torasemide in combination with 20 mg i.v. butizid. Administration of
torasemide alone significantly (P < 0.01) increased mean cumulative 24-hour excretion of
sodium (from 154 +/- 30 to 232 +/- 59 mmol/24 hr) and
chloride (from 128 +/- 21 to 233 +/- 84 mmol/24 hr) as compared with baseline.(ABSTRACT TRUNCATED AT 250 WORDS)