Double-blind comparison of primidone and phenobarbital in essential tremor.

In a double-blind cross-over trial, primidone was superior to both placebo and phenobarbital in reducing essential tremor in 13 patients. Phenobarbital, at a dosage yielding serum barbiturate levels greater than those seen with primidone, was not better than placebo. Thus, primidone has an effect in essential tremor independent from that of its metabolite phenobarbital.