Primidone [Desoxyphenobarbital; Primaclone]

Primidone pharmacotherapy has been commonly associated with dizziness, incoordination, lethargy, loss of appetite, nausea, vertigo, and vomiting. Concurrent primidone pharmacotherapy and pharmacotherapy with opiate analgesics, sedative-hypnotics, or other drugs that produce CNS depression may result in additive CNS depression. Prescribe primidone pharmacotherapy cautiously to patients who have the conditions listed in the “Cautions and Comments” section of the phenobarbital monograph. Primidone is metabolized to phenobarbital and phenobarbital and phenylethylmalonamide (PEMA). PEMA is more toxic than primidone and possesses relatively weak anticonvulsant activity. Primidone pharmacotherapy during pregnancy has been associated with various congenital malformations. Abrupt discontinuation of primidone pharmacotherapy may result in status epilepticus. The primidone dosage should be reduced gradually, unless therapeutically contraindicated, over a period of 2 weeks, until it is completely discontinued in order to reduce the risk for withdrawal seizures, including status epilepticus.