Primidone (Mysoline): Drug Monograph
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- Control of grand mal, psychomotor, and focal epileptic seizures, alone or with other anticonvulsants
- May control grand mal seizures refractory to other anticonvulsant therapy
- No prior antiepileptic therapy:
- Days 1-3: 100-125 mg at bedtime
- Days 4-6: 100-125 mg twice daily
- Days 7-9: 100-125 mg three times a day
- Days 10/maintenance: 250 mg three times a day
- Usual maintenance: 250 mg three or four times a day
- Maximum: 500 mg four times a day
- Already receiving other anticonvulsants:
- 100 to 125 mg at bedtime
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Increase gradually to maintenance dose as other drug is gradually decreased. Continue until satisfactory dosage level achieved or other medication is completely withdrawn. When therapy with primidone alone is the objective, transition from concomitant therapy should not be completed in <2 weeks
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Maximum: 2 g/day
- Grand mal, psychomotor, and focal epileptic seizures (alone or with other anticonvulsants), <8 years:
- Days 1-3: 50 mg at bedtime
- Days 4-6: 50 mg twice daily
- Days 7-9: 100 mg twice daily
- Days 10/maintenance: 125-250 mg three times a day
- Usual maintenance: 125-25- mg three or 10-25 mg/kg/day in divided doses
- ≥8 years, no prior antiepileptic therapy:
- Days 1-3: 100-125 mg at bedtime
- Days 4-6: 100-125 mg twice daily
- Days 7-9: 100-125 mg three times a day
- Days 10/maintenance: 250 mg three times a day
- Usual maintenance: 250 mg three or four times a day
- Maximum: 500 mg four times a day
- Already receiving other anticonvulsants:
- 100-125 mg at bedtime
- Increase gradually to maintenance dose as other drug is gradually decreased. Continue until satisfactory dosage level achieved or other medication is completely withdrawn. When therapy with primidone alone is the objective, transition from concomitant therapy should not be completed in <2 weeks.
- Maximum: 2 g/day
- None (per manufacturer)
- Other experts have suggested:
- CrCL ≥ 50 mL/min = give every 12 h
- CrCl 10 to 50 mL/min = give every 12 to 24 h
- CrCl < 10 mL/min = give every 24 h
- Abrupt withdrawal of antiepileptic medication may precipitate status epilepticus.
- Suicidal behavior and ideation
- Ataxia
- Vertigo
- Occasionally: nausea, anorexia, vomiting, fatigue, hyperirritability, emotional disturbances, sexual impotency, diplopia, nystagmus, drowsiness, and morbilliform skin eruptions.
- Rarely: granulocytopenia, agranulocytosis, and redcell hypoplasia and aplasia
- Pregnancy: Total daily dosage should not exceed 2 g. Complete blood count and a sequential multiple analysis-12 (SMA-12) test every 6 months. Effects of primidone in human pregnancy is unknown
- Labor and Delivery: None
- Nursing Mothers: Primidone appears in breast milk in substantial quantities. Nursing should be discontinued.
- Renal Impairment: None
- Hepatic Impairment: None
- Pediatric Patients: None
- Geriatric Patients: None
- Primidone appears in breast milk in substantial quantities. Nursing should be discontinued.
- Scientific Name: 5-ethyldihydro-5-phenyl-4,6 (1H, 5H) pyrimidinedione
- Empirical Formula: C12H14N2O2
- Molecular Weight: 218.25
- Primidone 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 per se 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.
- Absorption: > 90%
- Distribution: Vd 0.6 to 0.75 L/kg; Found in breast milk
- Metabolism: Phenobarbital, phenylethylmalonamide (metabolites)
- Elimination: Urine by 15% to 65% as unchanged drug
- Patients, their caregivers, and families should be counseled that primidone may increase the risk of suicidal thoughts and behavior. Symptoms of depressions may include any unusual changes in mood or behavior, the emergence of suicidal thoughts, behavior, or thoughts about self-harm. Behaviors of concern should be reported immediately to health care providers.
- Patients should be encouraged to enroll in the NAAED Pregnancy Registry if they become pregnant.
Indications
Dosing (Adult)
Dosing (Pediatric)
Renal Dosing
Warnings
Adverse Reactions
Special Populations
Breasfeeding
Chemical Structure
Mechanism of Action
Pharmacokinetics
Counseling Points
MESH Terms & Keywords
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