Background: The aim of the study was to evaluate the uricosuric effect of the angiotensin II receptor antagonist, losartan, in hypertensive patients with renal transplants who are treated with cyclosporin A (CsA).
Methods: Twenty-six patients with stable renal function and hypertension, 16 men and 10 women, median age 47 years (range, 25-63 years), were studied in an open randomized crossover trial, comparing a 2-week control period with a 2-week period of once-daily administration of 50 mg of losartan. The main outcome measurements were fractional excretion of uric acid (FE(uric acid)) based on 24-hr urine collections and plasma uric acid.
Results: The median FE(uric acid) was 5.7% (range, 2.4-10.4%) in the control period with a median change of +0.84% (range, -1.15% to +2.77%) in the losartan period (P<0.0002). Plasma uric acid was 0.47 mM (0.29-0.69 mM) in the control period with a change of -0.03 mM (-0.10 to 0.06 mM) in the losartan period (P<0.002). Diastolic blood pressure was 87 mmHg (70-97 mmHg) in the control period with a change of -3 mmHg (-13 to +6 mmHg) in the losartan period (P<0.005). There was no difference in systolic blood pressure between the two study periods. Plasma creatinine was 165 microM (102-356 microM) in the control period with a change of +9 microM (-36 to +60 microM) in the losartan period (P<0.01). Plasma potassium was 4.2 mM (3.0-4.7 mM) in the control period with a change of + 0.2 mM (-0.2 to +0.9 mM) in the losartan period (P<0.0005).
Conclusions: Once-daily administration of 50 mg of losartan in hypertensive CsA-treated patients with renal transplants caused a 17% increase in FE(uric acid) and an 8% fall in plasma uric acid.