Acute interstitial nephritis following treatment with anorectic agents phentermine and phendimetrazine.

A 47-year-old mildly obese female began a weight reduction program that included anorectic therapy with phentermine and phendimetrazine. A normal urinalysis and serum creatinine were documented at the start of therapy. After three weeks of treatment, the patient felt ill and discontinued her treatment. Subsequently she was found to have leukocyturia, a rash on her face and chest, and a rise in her serum creatinine from 0.8 mg/dl to 2.1 mg/dl. A renal biopsy confirmed the diagnosis of acute interstitial nephritis. The patient was treated with corticosteroids and her renal function returned to normal. Despite the recent withdrawal of two anorectic agents due to data linking them to severe cardiac and pulmonary disease, the appetite suppressants phentermine and phendimetrazine remain in widespread usage for the treatment of obesity. This case represents the first report of acute interstitial nephritis associated with phentermine or phendimetrazine.

Effect of acute changes in glomerular filtration rate on Na+/H+ exchange in rat renal cortex.

Studies were undertaken in Munich-Wistar rats to assess the influence of changes in filtered bicarbonate (FLHCO3), induced by changes in GFR, on Na+/H+ exchange activity in renal brush border membrane vesicles (BBMV). Whole-kidney and micropuncture measurements of GFR, FLHCO3, and whole-kidney and proximal tubule HCO3 reabsorption (APRHCO3) were coupled with BBMV measurements of H+ gradient-driven 22Na+ uptake in each animal studied. 22Na+ uptake was measured at three Na+ concentration gradients to allow calculation of Vmax and Km for Na+/H+ exchange. GFR was varied by studying animals under conditions of hydropenia, plasma repletion, and acute plasma expansion. The increase in GFR, FLHCO3, and APRHCO3 induced by plasma administration correlated directly with an increase in the Vmax for Na+/H+ exchange in BBMV. The Km for sodium was unaffected. In the plasma-expanded rats, the Vmax for Na+/H+ exchange was 22% greater than in the hydropenic rats (P less than 0.025) whereas APRHCO3 was 86% greater (P less than 0.001). These results indicate that increases in FLHCO3, induced by acute increases in GFR, stimulate Na+/H+ exchange activity in proximal tubular epithelium. This stimulation is a mechanism which can, in part, account for the delivery dependence of proximal bicarbonate reabsorption.

Encainide-induced encephalopathy in a patient with chronic renal failure.

A report of encainide-induced encephalopathy in a patient with chronic renal failure is presented. Drug encephalopathy has been previously reported with various agents, but not with encainide. The patient improved after withdrawal of encainide.