Primidone Dosage

Usual Adult Dose for Seizures

Days 1 to 3: 100 to 125 mg orally at bedtime

Days 4 to 6: 100 to 125 mg orally twice a day

Days 7 to 9: 100 to 125 mg orally three times a day

Day 10 onward: 250 mg orally three to four times a day, increasing up to five or six times a day if necessary, not to exceed 500 mg four times a day (2 g/day).

Usual Pediatric Dose for Seizures

Neonates:
12 to 20 mg/kg/day in 2 to 4 divided doses, beginning with lower dosage and titrating upward

Children:
Less than 8 years:
Initial dose: 50 to 125 mg/day given at bedtime and increased by increments of 50 to 125 mg/day every 3 to 7 days
Maintenance dose: 10 to 25 mg/kg/day in 3 to 4 divided doses

Greater than or equal to 8 years:
Initial dose: 125 to 250 mg/day at bedtime and increased by increments of 125 to 250 mg/day every 3 to 7 days
Maintenance dose: 750 to 1500 mg/day in 3 to 4 divided doses
Maximum dose: 2 g/day

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Data not available

Dose Adjustments

For patients already receiving other anticonvulsants:

Start with 100 to 125 mg at bedtime, gradually increasing to a maintenance level as the other drug is decreased. The regimen should be continued until a satisfactory dosage level is achieved for the combination or until the other medication is completely withdrawn. The transition to primidone monotherapy should not be completed in less than two weeks.

Precautions

Primidone is contraindicated in patients with porphyria and patients who are hypersensitive to phenobarbital.

Abrupt withdrawal of antiepileptic medications may lead to status epilepticus.

Dialysis

Data not available

Other Comments

The manufacturer recommends a complete blood count (CBC) and sequential multiple analysis 12 (SMA-12) every 6 months if a patient is to remain on primidone therapy.

The therapeutic efficacy of a dosage regimen may take several weeks before it can be assessed.

See also...