Relationship between acetazolamide blood concentration and its side effects in glaucomatous patients

Although acetazolamide, a carbonic anhydrase inhibitor, has an effect of lo wering intraocular pressure, a number of side effects have been reported. T herefore, we investigated the relationship between the concentration of ace tazolamide and its side effects, including plasma electrolyte imbalance. Th is study was conducted on 23 glaucomatous patients who received repeated do ses of oral acetazolamide for one week or more. The concentrations of total and unbound plasma acetazolamide, as well as in the whole blood from the p atients, were measured by high-performance liquid chromatography. The serum creatinine concentration, electrolyte concentrations, and adverse reaction s were monitored. We found that plasma concentrations of chloride ion after repeated doses became higher than the normal range. This chloride ion conc entration significantly correlated with the acetazolamide concentration in the erythrocytes, but not with the plasma concentration. The patients with erythrocyte acetazolamide concentration more than 20 mu g/ml had higher inc idences of the side effects. Periodical monitoring of erythrocyte acetazola mide concentration and plasma chloride ion can be easily and safely applied to elderly glaucomatous patients treated with acetazolamide for long perio ds to prevent overdosage and side effects.