APPROPRIATENESS OF ANTIEPILEPTIC DRUG LEVEL MONITORING

Objectives.-To develop explicit, reliable appropriateness criteria for antiepileptic drug level monitoring and to assess the appropriateness of monitoring in one tertiary care institution. Design.-Appropriatene ss criteria derived from the literature and through expert opinion wer e used to evaluate a stratified random sample of antiepileptic drug le vel determinations obtained from chart review. Setting.-Tertiary care center performing more than 10 000 antiepileptic drug level determinat ions per year. Patients.-A total of 330 inpatients in whom antiepilept ic drug levels were measured a total of 855 times. Methods.-Drug level s were assessed at least 200 times for each of four antiepileptic drug s (phenytoin, carbamazepine, phenobarbital, and valproic acid). Main O utcome Measures.-The proportion of antiepileptic drug levels with an a ppropriate indication and, of those, the proportion sampled appropriat ely. Results.-Overall, 27% (95% confidence interval, 24% to 30%) of le vels had an appropriate indication. Interrater agreement for appropria teness was substantial (kappa=0.61). There was no significant differen ce in the appropriateness rate among the four drugs (range, 25% to 29% ), Of the 624 antiepileptic drug level determinations considered inapp ropriate (73%), only four (0.6%) were more than 20% higher than the up per limit of normal, and none of the four patients had clinical signs of drug toxicity, A median of six levels (range, one through 69) was d etermined per patient, and the median interval between level determina tions was 24 hours. Of the 27% of level determinations with an appropr iate indication, 51% were sampled correctly, resulting in an overall a ppropriateness rate of 14%. Conclusions.-Only 27% of antiepileptic dru g level determinations had an appropriate indication, and half of thes e were not sampled correctly. Routine daily monitoring without pharmac ological justification accounted for most of the inappropriate drug le vel determinations. Efforts to decrease inappropriate monitoring may r esult in substantial cost reductions without missing important clinica l results.