The pharmacokinetics of acetazolamide during CAPD

Acetazolamide is a carbonic anhydrase inhibitor commonly used to reduce intraocular pressure (IOP). We report the first pharmacokinetic study of acetazolamide in a patient undergoing continuous ambulatory peritoneal dialysis (CAPD). The patient was a Type I diabetic with end-stage renal disease (ESRD) undergoing CAPD who received acetazolamide for elevated IOP after surgery for a detached retina. Serum acetazolamide concentrations were measured prior to a 250 mg oral dose and 12 additional times during a 24-h dosing interval. All dialysate effluent was collected and assayed for acetazolamide. Serum concentrations at the beginning and end of the dosing interval were 18 and 17 mcg/mL, respectively, with a maximum concentration of 27 mcg/mL at 6.5 h (therapeutic range = 5-10 mcg/mL). The elimination half-life was prolonged, 28.5 h, compared to that seen in subjects with normal renal function (5-10 h). CAPD did not remove a clinically significant amount of drug (17.1 mg, or 6.8% of dose recovered in dialysate). The patient was very lethargic during therapy, a possible manifestation of acetazolamide toxicity. Marked reduction in acetazolamide dosage (in this case, 125 mg/day) would be required to prevent drug accumulation and toxicity.