Oliguric Renal Failure Associated with Benoxaprofen

Dr. James K. Onwubalili, MRC Research Fellow and Senior Registrar, Division of Communicable Diseases, Clinical Research Centre and Northwick Park Hospital, Watford Road, Harrow, Middx, HA1 3UJ (England) Sir, Benoxaprofen was withdrawn in Britain in August 1982 following reports of over 3,500 adverse reactions including 61 deaths accumulated since its introduction in 1980. Fatal cases of cholestatic jaundice and renal failure were among these reactions, predominantly affecting elderly patients [1–3]. In none of these cases was renal failure attributed to a tubulo-interstitial nephritis. We would like to document a further case of acute renal failure due to allergic interstitial nephritis, associated with blood eosinophilia, skin rash and mouth ulceration, which followed exposure to benoxaprofen. Case Report A 60-year-old widow with long-standing seronegative arthritis was started on benoxaprofen 600 mg daily with much improvement in her symptoms. Her previous history included a partial gastrectomy and vagotomy for chronic duodenal ulceration, a total right hip arthro-plasty for a femoral neck fracture, and severe grief reaction and depression for which she had been receiving fluphenazine and maproti-line for 2 years. 2 weeks after starting benoxaprofen she was admitted into her local hospital with a history of dysuria, dark urine and a pruritic rash. Physical examination showed a generalised morbilli-form rash, mouth ulceration and pyrexia of 37.5 °C. She passed only 480 ml of blood-stained urine in the ensuing 24 h. A midstream urine culture confirmed a coliform urinary infection. Her haemoglobin was 10.9 g/dl, white cell count 5.5 × 103/μl with 35% eosinophils (total = 1,925, normal = 40–400/μl), and platelet count 200 × 103/μl. Plasma sodium was 136 mmol/l, potassium 5.0 mmol/l, bicarbonate 21 mmol/l and urea 9.8 mmol/l. Benoxaprofen, fluphenazine and maprotiline were discontinued and she was treated with chlorpheniramine for the rash and amoxycillin for the urinary infection, and discharged. 1 week later she was readmitted as an emergency with anuria of 48 h duration and promptly transferred to our renal unit. Examination showed a resolving skin rash, mouth ulcers and oedema of both legs. Blood pressure was 130/70 mm Hg. Haemoglobin was 8.4 g/dl, white cell count 5.9 × 103/μl with 10% eosinophils (total = 590), platelet count 250 × 103/μl, plasma sodium 136 mmol/l, potassium 8.6 mmol/l, urea 50.5 mmol/l, serum creatinine 1.3 mmol/l, calcium 2.0 mmol/l, phosphate 2.2 mmol/l and urate 0.4 mmol/l. Peritoneal dialysis was commenced immediately. Her 24-hour