Get your patient on Primidone - Primidone tablet (Primidone)

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.

Adult 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 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 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.

In 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be continued until satisfactory dosage level is achieved for the combination, or the other medication is completely withdrawn.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 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.

Primidone is contraindicated in: 1) patients with porphyria and 2) patients who are hypersensitive to phenobarbital (see ACTIONS ) .

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.

Anticonvulsant

Chemical name: 5-ethyldihydro-5-phenyl-4,6 (1H,5H)-pyrimidinedione. Structural formula:

Primidone, USP is a white, crystalline, highly stable substance, M.P. 279 – 284°C. It is poorly soluble in water (60 mg per 100 mL at 37°C) and in most organic solvents. It possesses no acidic properties, in contrast to its barbiturate analog.

Each tablet, for oral administration, contains 50 mg of primidone, USP. In addition, each tablet contains the following inactive ingredients: lactose monohydrate, methylcellulose, acacia, sodium starch glycolate, and magnesium stearate.

Primidone Tablets USP, 50 mg are available as white, round, flat faced, beveled edge, scored tablets debossed LAN over 1301, supplied in bottles of 90 tablets.

90 Tablets                    NDC 62135-468-90

Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].

Dispense in a well-closed container as defined in the USP with a child-resistant closure.

Dispense with Medication Guide available at: www.chartwellpharma.com/medguides

Manufactured for:

Chartwell RX, LLC.

Congers, NY 10920

L71315

Revised: 04/2023