The Combined Diuretic Action of Quinethazone and Furosemide in Congestive Heart Failure

The combined diuretic action of quinethazone and furosemide has been studied in 24 patients with congestive heart failure maintained on a constant diet. The study was performed as a permutation trial test in which the error variance is reduced while permitting the examination of drug effects separate from the variations due to different patients and varying sequence of administration of drugs. The diuretic response to single drugs and to the combination of drugs in half doses showed exactly the same trend in 12 patients with slight to moderate degree of sodium retention as in 12 patients with severe sodium retention given double doses of diuretics. The results obtained indicate an additive effect of the combination of diuretics in terms of osmolal clearance, urinary sodium and chloride output as well as in terms of the development of hypochloraemic, hypokalemic alkalosis. The diuretic action of furosemide differed significantly from that of quinethazone. The renal tubular response to furosemide was characterized by: ( a ) a larger increase in natriuresis with rising doses; ( b ) a significant decrease of tubular reabsorption of solute free water; and ( c ) a shorter duration of action. Apparently the combined effect of the two drugs is most easily explained when it is assumed that the two diuretics, at least in part, inhibit renal tubular sodium reabsorption at different sites in the nephron. The combination of quinethazone and furosemide may prove useful in the treatment of refractory cardiac oedema when precautions are taken to avoid serious electrolyte disturbances.