Nurses Compass
Drug Guide
Trimethadione
Classification
Therapeutic: Anticonvulsant
Pharmacological: Hydantoin derivative
FDA Approved Indications
- Absence seizures (petit mal)
Mechanism of Action
Trimethadione reduces neuronal hyperexcitability by inhibiting T-type calcium channels, thereby suppressing abnormal electrical activity associated with absence seizures.
Dosage and Administration
Adult: Initial dose: 300 mg twice daily, titrate based on response and tolerability.
Pediatric: Same as adults; dosing based on weight and age, usually starting at 150-300 mg/day divided into multiple doses.
Geriatric: Use with caution due to potential for increased side effects; start at lower doses and titrate slowly.
Renal Impairment: Adjust dose as needed; monitor renal function.
Hepatic Impairment: Use cautiously; no specific adjustments but monitor liver function.
Pharmacokinetics
Absorption: Rapidly absorbed from gastrointestinal tract.
Distribution: Widely distributed in body tissues, crosses the blood-brain barrier.
Metabolism: Metabolized minimally in the liver.
Excretion: Primarily excreted unchanged in urine.
Half Life: Approximately 50-72 hours in adults, allowing for once or twice daily dosing.
Contraindications
- Hypersensitivity to trimethadione or related compounds.
- History of blood dyscrasias.
Precautions
- Monitor blood counts regularly due to risk of blood dyscrasias.
- Use with caution in hepatic or renal impairment.
- Pregnancy Category D: risk to fetus; weigh benefits vs. risks.
Adverse Reactions - Common
- Drowsiness, dizziness (Common)
- Gastrointestinal disturbances (Common)
Adverse Reactions - Serious
- Blood dyscrasias (aplastic anemia, agranulocytosis) (Rare)
- Hepatotoxicity (Rare)
- Dermatological reactions, including Stevens-Johnson syndrome (Rare)
Drug-Drug Interactions
- CNS depressants, increasing sedation.
- Valproic acid may increase serum levels of trimethadione.
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Monitor seizure frequency, blood counts, liver and renal function.
Diagnoses:
- Risk for injury due to seizures or adverse effects.
- Impaired laboratory parameters (blood counts, liver enzymes).
Implementation: Administer with food to reduce gastrointestinal upset. Educate patient on adherence and side effects.
Evaluation: Assess seizure control and monitor for adverse effects regularly.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Report signs of blood dyscrasias (e.g., sore throat, fever, unusual bleeding).
- Avoid alcohol and CNS depressants.
- Regular blood tests are necessary.
Special Considerations
Black Box Warnings:
- Risk of blood dyscrasias, including aplastic anemia and agranulocytosis.
Genetic Factors: No specific genetic factors identified.
Lab Test Interference: May falsely elevate certain laboratory liver and blood parameters.
Overdose Management
Signs/Symptoms: Drowsiness, ataxia, nausea, vomiting, dizziness, or coma in severe cases.
Treatment: Supportive care, activated charcoal if early, and close monitoring. Hemodialysis may be considered in severe overdose.
Storage and Handling
Storage: Store at room temperature, 20-25°C (68-77°F).
Stability: Stable under recommended storage conditions; check expiry date.