Primidone is used to treat seizures and essential tremor. It is metabolized into two active compounds — phenobarbital and phenylethylmalonamide (PEMA) — and both primidone and phenobarbital contribute to its effects and side effects.
This test is used to confirm therapeutic levels, evaluate suspected toxicity, guide dose adjustments, and assess medication adherence. Phenobarbital levels are often measured simultaneously because they significantly influence efficacy and side effects. Sample type is serum.