Losartan, the first angiotensin II receptor antagonist, is used to treat hypertension. We report a case of renal impairment associated with this drug.

A 77-year-old woman began receiving losartan, 50 mg/d, for hypertension. Concomitant medications included long-term use of allopurinol for gout. The patient's serum creatinine level at that time was 132.6 µmol/L (1.5 mg/dL). Six weeks later, the patient was hospitalized with a 1- to 2-week history of diarrhea and anorexia. On admission, her serum creatinine level was 327.1 µmol/L (3.7 mg/dL), and her blood urea nitrogen level was 36.1 mmol/L (101 mg/dL). The patient was oliguric for the following 3 days, and serum creatinine and blood urea nitrogen levels increased to 424.3 µmol/L (4.8 mg/dL) and 43.6 mmol/L (122 mg/dL), respectively. Results of renal ultrasonography showed no significant changes compared with results from 2 years earlier. After the patient began receiving diuretics and after losartan and allopurinol therapies were discontinued, renal function returned to levels near baseline.

Pharmacologic blockade of angiotensin II can lead to deterioration of renal function in patients at risk (those with preexisting renal impairment, concomitant use of diuretics, or congestive heart failure). Our patient had a history of type II diabetes and known diffuse vascular disease and thus was at risk for this event. A small right kidney suggested renal vascular disease. In one study [1], renal function deteriorated with angiotensin-converting enzyme inhibitors. Because losartan has a similar pharmacologic result—blockade of the renin-angiotensin-aldosterone system—it may be expected to produce a similar renal effect. A search of the MEDLINE database for reports published from 1980 to 1995 showed no case reports of renal impairment associated with losartan. When prescribing losartan for patients at risk for renal failure, clinicians should be aware of the possibility of renal impairment.