Primidone

INDICATIONS AND USAGE Primidone, used alone or concomitantly with other anticonvulsants, is 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 Usual Dosage Patients 8 years of age and older who have received no previous treatment may be started on primidone 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 twice a day Days 7 to 9: 100 to 125 mg three times a day Day 10 to maintenance: 250 mg three times a day For most adults and children 8 years of age and over, the usual maintenance dosage is three to four 250 mg primidone tablets 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 µg/mL. INITIAL: ADULTS AND CHILDREN OVER 8 KEY: •=50 mg tablet; ●=250 mg tablet Day 1 2 3 4 5 6 AM •• •• •• NOON PM •• •• •• •• •• •• DAY 7 8 9 10 11 12 AM •• •• •• ● Adjust to Maintenance NOON •• •• •• ● PM •• •• •• ● Patients Already Receiving Other Anticonvulsants Primidone 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be continued until satisfactory dosage level is achieved for the combination, or the other medication is completely withdrawn.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 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 twice a day Days 7 to 9: 100 mg twice a day Day 10 to maintenance: 125 mg three times a day to 250 mg three times a day 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.

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 Oxford Pharmaceuticals, LLC at 1-844-508-1455, 8:00 AM to 4.30 PM ET, Monday – Friday or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.