Hemodialysis of mefenamic acid in uremic patients

The effect of hemodialysis on plasma mefenamic acid levels was studied in four patients on long-term hemodialysis. A 500-mg oral dose of mefenamic acid was administered to the fasting patients two hours before hemodialysis. Arterial and venous blood samples taken before dialysis, at 30-minute intervals during a three-hour dialysis, and immediately before termination of dialysis were assayed by high-performance liquid chromatography. Mefenamic acid half-life on hemodialysis was not reduced substantially compared with that reported for normal patients. The extraction efficiency of the hollow-fiber kidneys averaged 6.4%. The mean drug recovery was 1.03 mg or 0.2% of the administered dose. The extensive plasma protein binding (range: 85-97%) accounted for the poor recovery. The study suggests that adjustment of mefenamic acid dosage is not necessary in patients undergoing hemodialysis and that hemodialysis is of minimal value in the management of mefenamate overdose.