Baclofen toxicity associated with declining renal clearance after ibuprofen

A 64-year-old male with an incomplete spinal cord injury had been taking baclofen 20 mg tid for 2 1/2 months without side effects. His blood urea nitrogen and serum creatinine rose from 13 and 0.9 mg%, respectively, to 59 and 2.8 mg% after ibuprofen 600 mg tid was begun. The patient displayed baclofen toxicity, developing confusion, disorientation, bradycardia, and hypothermia. His blood pressure dropped and he complained of blurred vision. Ibuprofen discontinuation and fluid repletion corrected the renal indices. Rapid tapering of baclofen was accompanied by reversal of baclofen toxicity. Patients taking baclofen must be monitored closely for toxicity when declining renal function is present. Clinicians should be alert to the possibility of renal insufficiency developing when ibuprofen is initiated. This case demonstrates the potential for ibuprofen-induced renal insufficiency to reduce baclofen clearance, thereby leading to baclofen toxicity. Published reports of ibuprofen-induced renal insufficiency are reviewed and pertinent pharmacokinetics of baclofen discussed.