Abstract
Phenytoin is an anticonvulsant commonly prescribed for prophylaxis and the treatment
of patients with generalized or partial seizures. Therapeutic drug monitoring of
phenytoin is mandatory owing to its narrow therapeutic range, long duration to achieve
steady-state plasma drug concentration, wide range of pharmacokinetic parameters and
non-linear pharmacokinetics. This descriptive study was carried out to determine the
patients’ compliance in taking phenytoin at the Promkiri Hospital epileptic out-patient
clinic during the period March to July 2007. The subjects were 75 patients aged 18-60
years; the male to female ratio was 1.58:1, with their average body weight being 46.07 kg,
and all had normal liver and renal functions. The dose of phenytoin used varied from 100
to 500 mg/day; the median dose was 300 mg/day. Drug non-compliance was verified in
15 patients (20 per cent of the subjects ) from pill counting, missing drug-taking days, and
checking serum phenytoin concentrations. The result of this study would lead to urgent
planning implemented for future patients’ therapy in order to improve the success rate in
the administration of phenytoin.
