Classes
DEA Class; Rx
Common Brand Names; Mysoline
- Anticonvulsants, Barbiturates;
- CYP3A4 Inducer, Strong
Description
Oral anticonvulsant related to barbiturates; metabolized to phenobarbital and another active metabolite; effective in all seizure disorders except absence; close monitoring for emerging or worsening suicidal thoughts/behavior or depression is recommended.
Indications
Indicated for use as an alternative to other anticonvulsants for the management of generalized tonic-clonic seizures, or for the management of complex partial seizures (e.g., psychomotor seizures).
Contraindications
Porphyria
Hypersensitivity to phenobarbital
Adverse Effects
Dysarthria
Paresthesia
Ataxia
Vertigo
Pediatric patients
- Paradoxical excitement
- Hyperactivity
Geriatric patients
- Excitement
- Confusion
- Depression
Adverse effects that decrease with continued treatment
- Drowsiness
- Ataxia
- Irritability
- Headache
- Restlessness
- Nystagmus
- Dizziness
- Vertigo
Warnings
Do not interchange brands, due to bioequivalence issues
When replacing another antiseizure drug, gradually increase dosage of primidone while gradually decreasing dosage of other drug over at least 2 weeks
Withdraw gradually, due to risk of precipitation of status epilepticus
Limited number of reports indicate maintaining serum concentration of 5-12 mcg/mL is necessary
Inhibits transplacental vitamin K transport, leading to increased risk of fetal hemorrhage
May render OCPs ineffective
May cause CNS depression; caution performing tasks that require mental alertness, including heavy machinery
Use cautioin in patients with clinical depression; Increased risk of suicidal thoughts or behavior reported; monitor patients for notable changes in behavior indicating suicidal thoughts or depression; inform healthcare provider immediately if symmptoms occur
Pregnancy and Lactation
Pregnancy category: D; continue use if pregnant; consider vitamin K supplementation for 1 month before birth
Lactation: Distributed in breast milk; discontinue if drug effects occur in nursing infant
Maximum Dosage
As with all anticonvulsant-type medications, primidone dosage must be individualized. The following are the maximum dosage limits recommended by the manufacturer:
2000 mg/day PO.
2000 mg/day PO.
2000 mg/day PO.
>= 8 years: 2000 mg/day PO.
< 8 years: 25 mg/kg/day PO or 1000 mg/day PO.
25 mg/kg/day PO.
20 mg/kg/day PO.
How supplied
Primidone
tablets
- 50mg
- 250mg