Renal Effects of Aspirin are Clearly Dose-Dependent and are of Clinical Importance from a Dose of 160 mg

BACKGROUND: High doses of aspirin counteract the beneficial effects of angiotensin-converting enzyme (ACE) inhibitors. It is not known how low-dose aspirin, with concomitant ACE-inhibitor treatment, affects renal function. AIM: To study renal effects of different doses of aspirin in elderly healthy volunteers who had an activated renin-angiotensin system. METHODS: Sixteen subjects each received two different doses of aspirin (0 and160 mg or 80 and 320 mg) after pre-treatment with bendroflumethiazide and enalapril, in a randomised double-blind, cross-over fashion. RESULTS: Least square means of the observations 30 to 180 min after dosing, showed that urine flow, GFR, excretion rates of sodium, osmolality clearance and free water clearance were significantly decreased in a dose-dependent manner. Urine flow, sodium excretion rate and free water clearance were significantly lower with 320 mg aspirin vs. 0 mg and 80 mg, and GFR was significantly lower with 320 mg vs. 80 mg. Urine flow, sodium excretion rate, free water and osmolality clearance was significantly lower with aspirin 160 mg vs. 0 mg. CONCLUSION: The dose-dependent renal effects of aspirin are of clinical importance from a dose of 160 mg. The adverse influence of aspirin doses higher than 80 mg should be taken into consideration in patients with heart failure.