Effects of rhein on renal arachidonic acid metabolism and renal function in patients with congestive heart failure

Summary In a randomized double-blind cross-over study the effects of rhein (administered as diacetylrhein 50 mg b.d. for 5 days) and placebo on renal arachidonic acid metabolism and renal function have been compared in 12 elderly patients (mean age 75.2 years) with congestive heart failure, whose renal function was known to be dependent on the integrity of the renal prostaglandin system.Rhein like placebo, did not induce any change in the urinary excretion of prostaglandin (PG) E₂, 6-keto-PGF₁ and thromboxane (TX) B₂, nor did it affect creatinine clearance, blood urea, urine output, natriuresis, body weight, plasma renin activity or plasma aldosterone concentration. Separate analysis of the results obtained in the 5 patients receiving diuretic treatment did not show any significant effect of rhein as compared with placebo on the parameters investigated. Serum TXB₂ concentration during whole blood clotting, as an index of platelet arachidonic acid metabolism, also showed no significant difference when DAR and placebo were compared.It is concluded that in patients with congestive heart failure rhein does not inhibit renal or platelet eicosanoid metabolism, nor does it modify renal function, sodium excretion or the renal response to diuretics.