Interstitial Nephritis Induced by Cloxacillin

Dr. John F.S. Crocker, Professor of Pediatrics, IWK Hospital for Children, 5850 University Avenue, Halifax, Nova Scotia B3J 3G9 (Canada) Dear Sir, Interstitial nephritis due to drug exposure is a common cause of acute renal failure. Many members of the penicillin group of antibiotics have been implicated in this condition. Interstitial nephritis in patients receiving methicillin is the most publicized association but episodes have been reported with amoxicillin, oxacillin, flucloxacillin, dicloxacillin, carbenicillin, penicillin G, and ampicillin. We report a case of interstitial nephritis associated with the use of cloxacillin. Case Report The patient was a 4-year-old Caucasian male who presented to hospital with fever, irritability and decreased fluid intake and urination. He had been well until 28 days prior to admission (PTA) when he was prescribed a 10-day course of oral cloxacillin for a minor localized cellulitis on the foot. Five days after the completion of cloxacillin, he developed a fever and malaise. Eleven days PTA, the fever and listlessness recurred accompanied by a fine red truncal rash. He was seen by a pediatrician who diagnosed a bacterial cervical lymphadenitis and prescribed another course of oral cloxacillin 50 mg/kg/day × 7 days. The spiking fever subsided 8 days PTA but returned on the 5th day PTA. Anorexia, vomiting, and mild conjunctival injection were present on admission and he had been anuric for 48 h. Past history was unremarkable except for recurrent otitis media treated with amoxicillin. On examination he was lethargic, irritable and moderately dehy-trated with dry mucous membranes, a pulse rate of 90 bpm, blood pressure of 90/50 mm Hg, oral temperature of 38.8 °C, and weight of kg. There was no skin rash, lymphadenopathy, arthritis, or renomegaly on admission. Laboratory values included a WBC of 10V1 (27,500 mm3), (88% neutrophils, 2% band, 6% monocyte, 4% lymphocytes, and no eosinophils), Hbg 96 g/l (1.49 mmol/l), with a normal peripheral blood smear; Na 124 mmol/l; K 3.7 mmol/ 1, urea 39.3 mmol/l (109 mg/dl) creatinine 500 μmol/l (5.6 mg/dl). Urinalysis revealed a pH of 5.0, SG of 1.009, no glucose, protein or blood, 10–20 WBC casts/HPF, spot Na of 3 mmol/l, creatinine 4.4 mmol/l (50 mg/dl), Fractional excretion of sodium 0.3% and osmolality 253. A tentative diagnosis of prerenal azotemia secondary to dehydration from vomiting was entertained, so he was rehydrated overnight with normal saline. In the morning his weight was