Epiad, 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.
How it works
Epiad raises electro- or chemoshock seizure thresholds or alters seizure patterns in experimental animals. The mechanism(s) of primidone’s antiepileptic action is not known. Primidone has anticonvulsant activity as do its two metabolites, phenobarbital and phenylethylmalonamide (PEMA). In addition to its anticonvulsant activity, PEMA potentiates the anticonvulsant activity of phenobarbital in experimental animals.
Indications
Epiad, 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
Adult dosage
Patients 8 years of age and older who have received no previous treatment may be started on Epiad according to the following regimen.
Days 1-3: 100 to 125 mg at bedtime
Days 4-6: 100 to 125 mg b.i.d.
Days 7-9: 100 to 125 mg t.i.d.
Day 10-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 5-12 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be continued until satisfactory dosage level is achieved for the combination, or the other medication is completely withdrawn.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 Epiad alone is the objective, the transition from concomitant therapy should not be completed in less than two weeks.
Side Effects
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 redcell hypoplasia and aplasia, have been reported rarely.
Contraindication
Primidone is contraindicated in:
1) patients with porphyria and
2) patients who are hypersensitive to phenobarbital
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