Primidone (2 brand names, 1 dosage form, 1 route)
Available dosage forms: TABLET.
Routes of administration: ORAL.
Brand Names
- MYSOLINE
- PRIMIDONE
Indications and Usage
Primidone tablets used alone or concomitantly with other anticonvulsants, are indicated in the control of grand mal, psychomotor, and focal epileptic seizures. It may control grand mal seizures refractory to other anticonvulsant therapy.
Dosage and Administration
Adult Dosage Patients 8 years of age and older who have received no previous treatment may be started on primidone tablets according to the following regimen using either 50 mg or scored 250 mg primidone tablets: Days 1 to 3: 100 to 125 mg at bedtime.Days 4 to 6: 100 to 125 mg b.i.d.Days 7 to 9: 100 to 125 mg t.i.d.Day 10 to maintenance: 250 mg t.i.d. For most adults and children 8 years of age and over, the usual maintenance dosage is three to four 250 mg primidone tablets daily in divided doses (250 mg t.i.d. or q.i.d.). If required, an increase to five or six 250 mg tablets daily may be made but daily doses should not exceed 500 mg q.i.d. Dosage should be individualized to provide maximum benefit. In some cases, serum blood level determinations of primidone may be necessary for optimal dosage adjustment. The clinically effective serum level for primidone is between 5 to 12 mcg/mL. In Patients Already Receiving Other Anticonvulsants Primidone tablets should be started at 100 to 125 mg at bedtime and gradually increased to maintenance level as the other drug is gradually decreased. This regimen should be continued until satisfactory dosage level is achieved for the combination, or the other medication is completely withdrawn. When therapy with primidone tablets alone is the objective, the transition from concomitant therapy should not be completed in less than two weeks. Pediatric Dosage For children under 8 years of age, the following regimen may be used: Days 1 to 3: 50 mg at bedtime.Days 4 to 6: 50 mg b.i.d.Days 7 to 9: 100 mg b.i.d.Day 10 to maintenance: 125 mg t.i.d. to 250 mg t.i.d. For children under 8 years of age, the usual maintenance dosage is 125 to 250 mg three times daily or 10 to 25 mg/kg/day in divided doses.
Contraindications
Primidone is contraindicated in: 1) patients with porphyria and2) patients who are hypersensitive to phenobarbital (see CLINICAL PHARMACOLOGY).
Adverse Reactions
The most frequently occurring early side effects are ataxia and vertigo. These tend to disappear with continued therapy, or with reduction of initial dosage. Occasionally, the following have been reported: nausea, anorexia, vomiting, fatigue, hyperirritability, emotional disturbances, sexual impotency, diplopia, nystagmus, drowsiness, and morbilliform skin eruptions. Granulocytopenia, agranulocytosis, and red-cell hypoplasia and aplasia, have been reported rarely. These and, occasionally, other persistent or severe side effects may necessitate withdrawal of the drug. Megaloblastic anemia may occur as a rare idiosyncrasy to primidone and to other anticonvulsants. The anemia responds to folic acid without necessity of discontinuing medication. To report SUSPECTED ADVERSE REACTIONS, contact Amneal Pharmaceuticals at 1-877-835-5472 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.