Generic Name

Paramethadione

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Classification

FDA Approved Indications

• Partial seizures
• Generalized tonic-clonic seizures

Mechanism of Action

Paramethadione stabilizes neuronal membranes and inhibits repetitive firing by blocking sodium channels, thereby reducing seizure activity.

Dosage and Administration

Adult: Initial dose: 30 mg/kg/day divided into 2-3 doses. Adjust based on response and tolerability.

Pediatric: Starting dose typically 15-20 mg/kg/day in divided doses, titrated up as needed.

Geriatric: Use with caution; start at lower doses and titrate slowly due to decreased hepatic function and comorbidities.

Renal Impairment: Adjust dose based on renal function; specific guidelines not well established.

Hepatic Impairment: Use with caution; hepatic metabolism may be reduced.

Pharmacokinetics

Absorption: Well absorbed orally

Distribution: Widely distributed, crosses the blood-brain barrier

Metabolism: Primarily hepatic, via conjugation and oxidation

Excretion: Renally excreted mainly as conjugates

Half Life: Approximately 20-40 hours, allowing for once or twice daily dosing

Contraindications

• Hypersensitivity to paramethadione or other hydantoins
• Bone marrow depression
• Porphyria

Precautions

• Use with caution in hepatic dysfunction, pregnancy, and lactation; careful monitoring required.

Adverse Reactions - Common

• Drowsiness (Common)
• Dizziness (Common)
• Gastrointestinal upset (Common)

Adverse Reactions - Serious

• Blood dyscrasias (aplastic anemia, leukopenia, thrombocytopenia) (Rare)
• Hepatotoxicity (Rare)
• Stevens-Johnson syndrome (Rare)

Drug-Drug Interactions

• Valproic acid (may increase levels)
• Other anticonvulsants (additive CNS depression)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Take medication exactly as prescribed.
• Report signs of allergic reactions, bleeding, or liver problems.
• Avoid alcohol and CNS depressants; inform about potential drowsiness.

Special Considerations

Black Box Warnings:

• Serious blood dyscrasias and hepatotoxicity, though rare.

Genetic Factors: None specifically established.

Lab Test Interference: May cause false positive for urinary ketones.

Overdose Management

Signs/Symptoms: Drowsiness, nystagmus, coma, seizures.

Treatment: Supportive care; activated charcoal if recent ingestion; hemodialysis may be considered in severe cases.

Storage and Handling

Storage: Store at room temperature, away from light and moisture.

Stability: Stable under recommended conditions, check expiration date.