A Cochrane review included one open study with a total of 180 patients with newly-diagnosed, untreated epilepsy. The antiepileptic drugs used were carbamazepine, valproate, phenytoin, phenobarbital and primidone. A 12-month remission from seizures was achieved by 60% of the patients randomised to therapeutic drug monitoring (intervention group) and by 61% in the control group. A total of 56% in the intervention group and 58% in the control group were seizure free during the last 12 months of follow up. Adverse effects were reported by 48% in the intervention group and 47% of the control group patients. Of those randomised to therapeutic drug monitoring, 62% completed the two-year follow up compared with 67% of the control group.
Authors' comment: The lack of evidence to support routine antiepileptic drug serum concentration measurement does not exclude the possible usefulness of therapeutic drug monitoring of specific antiepileptic drugs during polytherapy, in special situations or in selected patients.