Primidone
Brand Name: Mysoline
Generic Available
Common Dosage Forms:
Tablets: 50 mg, 250 mg
Suspension: 250 mg/5 mL
FDA Indications/Dosages:
For the control of grand mal, psychomotor of focal epileptic seizures, either alone or with other anticonvulsants: Adult dosage for those without previous treatment: Days 1-3: 100-125 mg at bedtime; days 4-6: 100-125 mg twice daily; days 7-9: 100-125 mg three times daily; day 10-maintenance: 250 mg 3-4 times daily. May increase to 250 mg 5-6 times daily.
Pharmacology/Pharmacokinetics: Primidone’s mechanism of action is unknown. It is known to raise electro- and chemoshock seizure thresholds and alter seizure patterns in animals. It is metabolized after absorption to phenobarbital and phenylethylmalonamide (PEMA). It, along with its metabolites, may act by producing sensory cortex depression through inhibition of conduction in the reticular formation at the level of the thalamus. This may be due to a GABA-like action of increased chlorine conductase.
Drug Interactions: CNS depressants and ALCOHOL will have additive effects. Valproic acid may increase serum levels. May increase the metabolism of oral ANTICOAGULANTS, beta-blockers, estrogens including oral contraceptives, corticosteroids, doxycycline, griseofulvin, quinidine, and theophylline. May potentiate methoxyflurane renal toxicity.
Contraindications/Precautions: Use is contraindicated in patients hypersensitive to barbiturates and in patients with a history of manifest or latent porphyria. Use with caution in pregnancy, in the elderly or debilitated, and in patients with impaired liver function. May increase the incidence of suicidal thoughts or behavior during therapy. Pregnancy Category D.
Adverse Effects: Dizziness, ataxia, nausea, vomiting, drowsiness, and impotency.
Patient Consultation:
May cause dizziness. Use caution while operating machinery or when mental alertness is required.
Avoid alcohol while taking this medication.
Store in a cool, dry place away from sunlight and children.
If a dose is missed, take it as soon as possible. If it is closer to the time of your next dose than the dose you missed, skip the missed dose and return to your dosing schedule. Do not double doses.
Contact a physician if the above side effects are severe or persistent.