The usual course of achieving approval for a drug is to make known it is cogent at what time compared against placebo, or that it is more effective than an existing drug. In monotherapy (where only one drug is taken) it is not ethical to conduct a trial with placebo upon a new drug of uncertain efficacy.

This is because untreated epilepsy foliage the patient at significant risk of dying. Therefore, almost all new epilepsy anti convulsants drugs are initially approved only as adjunctive (add-on) therapies. Patients who's epilepsy is publicly uncontrolled by their medication (i.e., it is stubborn to treatment) are selected to see if supplementing the medication with the new drug leads to an improvement in hold control. Any reduction in the frequency of seizures is compared against a placebo.

Once in that place is confidence that a drug is likely to subsist effective in monotherapy, trials are conducted where the drug is compared to some existing standard.

For partial-onset seizures, this is typically carbamazepine. Despite the launch of over ten drugs since 1990, no starting anew drug has been shown to be more sufficient than the older harden, which includes carbamazepine, valproate and phenytoin. The lack of superiority extremely existing treatment, combined with the lack of placebo-controlled trials, means that few modern drugs have earned FDA approval as initial monotherapy. In striking difference, Europe only requires equivalence to existing treatments, and has approved various more.