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    DEA Class;  Rx

    Common Brand Names; Mysoline

    • Anticonvulsants, Barbiturates; 
    • CYP3A4 Inducer, Strong

    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.

    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).

    For the treatment of essential tremor.


    Hypersensitivity to phenobarbital





    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

    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 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

    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.



    • 50mg
    • 250mg