Ann. Pak. Inst. Med. Sci. 2010; 6(1): 11-14

Objectives: To evaluate the effects of Low dose Aspirin (LDA) 75mg/day on renal function and uric acid (UA) handling in elderly patients with normal renal function.
Study Design: Case control study.
Place and Duration: This study was conducted at the Cardiology and Medical clinics of Pakistan Institute of Medical Sciences (PIMS), Islamabad over a period of four months.
Materials and Methods: Sixty elderly patients with the Mean age 58.9±6.82 years and range 50-75 years were divided equally in case and control groups. The case group received LDA 75mg/day for two weeks and then discontinued. The control group did not receive aspirin. Patients were excluded if they had serum creatinine (Scr) more than 1.5mg/dl and glomerular filtration rate (GFR) less than 90ml/min determined by MDRD equation or had a contraindication to aspirin use. Blood samples were tested at base line, at 2 weeks of aspirin therapy, and at 4 weeks (i.e. after 2 weeks of cessation of aspirin) for serum levels of urea, creatinine, uric acid and GFR, estimated by both Cockroft-Gault (CG) and MDRD equation.
Results: The base line renal function in aspirin and control group did not differ. After 2 weeks of aspirin therapy only serum UA increased significantly from base line in aspirin group (33.7%) vs. control group (6.14%), mean change 1.607±1.797 vs. 0.28±1.342, respectively (P=0.008), while serum urea , creatinine and GFR remained unchanged in the two groups. After 2 weeks of cessation of aspirin, serum UA returned to base line value in aspirin group and serum urea, creatinine and GFR did not change from base line in two groups.
Conclusion: Short term low dose aspirin 75mg/day does not affect renal function in elderly patients who have normal renal functions at baseline and does not require renal function monitoring.
Key Word: Low Dose Aspirin Prophylaxis, Elderly, Renal function

Introduction

Cardiovascular disease (CVD) is the leading cause of mortality in the world. National organizations have published guidelines recommending the use of aspirin for secondary and primary prevention of cardiovascular events including coronary artery disease, transient ischemic attack, ischemic stroke and peripheral arterial disease and diabetes mellitus over age 40.^1-5
The optimal dose for CVD prevention remains uncertain between 75-150mg/day and guidelines do not advocate a particular dose. Meta-analysis of aspirin trials have not shown clear additional benefit of aspirin doses greater than 75mg/day for prevention of cardiovascular events, but risk of gastrointestinal toxicity and bleeding increases with escalating dose.⁶
Aspirin being a member of non steroidal anti-inflammatory drugs, shares its nephrotoxic potential due to cycloxygenase (COX) inhibition, whereby vasodilatory prostaglandin PG I2 and E2 production is suppressed, posing risk of increased toxicity in patients with such risk factors as diabetes mellitus, heart failure, renal dysfunction and elderly. The use of low dose aspirin (LDA) is expected to escalate in view of recent guidelines for prevention of CVD, particularly in older population. The renal effects of LDA in elderly patients have not been widely studied and only limited studies have addressed this issue with conflicting results.^7-12 So further studies are warranted to study the renal effects of LDA. The present study aimed to evaluate the effects of LDA 75mg on renal function and uric acid handling in elderly patients with normal renal functions and the requirement of routine monitoring of renal functions in this population.