Renal effects of low dose aspirin in elderly patients.

BACKGROUND

Aspirin is commonly used by elderly patients. In previous studies we found transient changes in renal function induced by low doses of aspirin.

OBJECTIVES

To investigate the mechanisms of these effects.

METHODS

The study group included 106 long-term care stable geriatric inpatients. Diet and drugs were kept stable. The study lasted 5 weeks; during the first 2 weeks 100 mg aspirin was administered once a day. Clinical and laboratory follow-up was performed at baseline and weekly for the next 3 weeks. The glomerular filtration rate was estimated by creatinine clearance measured in 24 hour urine and serum creatinine, and by the Cockcroft-Gault formula (C-G) equation. Uric acid clearance was determined from serum concentrations and 24 hour excretion of uric acid. Patients with serum creatinine > 1.5 mg/dl were not included.

RESULTS

After 2 weeks on low dose aspirin, measured creatinine and uric acid clearances decreased significantly compared with the initial values in 70% and 62% of the patients, respectively, with mean decreases of 19% and 17%, respectively (P< 0.001). Blood urea nitrogen increased by 17% while serum creatinine and uric acid concentrations increased by 4% (P < 0.05 for all). The C-G values decreased by 3% (P< 0.05). After withdrawal of aspirin all parameters improved. However, 67% of the patients remained with some impairment in their measured Ccr, compared to baseline. Patients who reacted adversely to low dose aspirin had significantly better pre-study renal function (Ccr), lower hemoglobin and lower levels of serum albumin.

CONCLUSIONS

Short-term low dose aspirin affected renal tubular creatinine and uric acid transport in the elderly, which may result in a prolonged or permanent deterioration of the renal function. It is suggested that renal functions be monitored even with the use of low dose aspirin in elderly patients.