Mysoline

Generic name: Primidone

Drug class: Barbiturate anticonvulsants

Dosage form: Oral tablet (50 mg, 125 mg, 250 mg)

Root of administration: Oral

Dose: For adults and children aged 8 years and older with no prior treatment:

– Days 1 to 3: 100 to 125 mg at bedtime.
– Days 4 to 6: 100 to 125 mg twice a day.
– Days 7 to 9: 100 to 125 mg three times a day.
– Day 10 to maintenance: 250 mg three times a day.

Maintenance dosage typically ranges from 750 mg to 1,500 mg per day, divided into three or four doses. The maximum daily dosage should not exceed 2,000 mg.

Mechanism of action: Primidone’s exact mechanism of action is not fully understood. It is believed to raise seizure thresholds by interacting with voltage-gated sodium channels, inhibiting high-frequency repetitive firing of action potentials. Its active metabolites, phenobarbital and phenylethylmalonamide (PEMA), also contribute to its anticonvulsant effects.

Drug usage cases:

• Control of grand mal (tonic-clonic) seizures
• Management of psychomotor (complex partial) seizures
• Treatment of focal (partial) seizures
• Adjunctive therapy for generalized tonic-clonic seizures refractory to other anticonvulsants
• Off-label use for essential tremor

Drug contraindications:

• Hypersensitivity to phenobarbital or primidone
• Porphyria

Side effects:

• Drowsiness
• Ataxia (lack of muscle coordination)
• Visual disturbances
• Nystagmus (involuntary eye movement)
• Headache
• Dizziness
• Nausea
• Vomiting
• Loss of appetite
• Irritability
• Impotence
• Sexual dysfunction
• Rare: Anemia (including megaloblastic anemia), agranulocytosis, and aplastic anemia
• Rare: Dermatological reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis
• Rare: Hepatic dysfunction
• Rare: Osteomalacia (softening of the bones)
• Rare: Dupuytren’s contracture (a condition causing the fingers to bend towards the palm)

Warnings:

• Risk of suicidal thoughts and behaviors; monitor for mood changes
• Potential for drowsiness and impaired coordination; caution when driving or operating machinery
• Risk of withdrawal seizures if discontinued abruptly; taper dosage gradually under medical supervision
• May cause drowsiness; avoid alcohol and other CNS depressants
• Use with caution in patients with hepatic or renal impairment
• Monitor for signs of blood dyscrasias (e.g., unexplained bleeding or bruising)
• May cause vitamin D deficiency leading to bone disorders; consider supplementation

Use during pregnancy or breastfeeding: Primidone is classified as a Category D medication during pregnancy, indicating a risk to the fetus. It should only be used if the potential benefit justifies the potential risk. Primidone is excreted in breast milk; caution is advised when administering to nursing mothers. Consult a healthcare provider to discuss potential risks and benefits.