Generic Name

Phensuximide

---

Classification

FDA Approved Indications

• Absence seizures (petit mal)

Mechanism of Action

Phensuximide works by inhibiting voltage-sensitive sodium channels in neurons, leading to suppression of abnormal neuronal firing that causes seizures.

Dosage and Administration

Adult: Initial dose of 250 mg twice daily, titrated based on response and tolerability.

Pediatric: Typically started at 10-20 mg/kg/day in divided doses, titrated cautiously.

Geriatric: Use with caution; start at lower doses and titrate slowly.

Renal Impairment: Adjust dose based on renal function; close monitoring recommended.

Hepatic Impairment: Use caution; no specific dosage adjustment but monitor liver function.

Pharmacokinetics

Absorption: Well absorbed orally.

Distribution: Widely distributed, crosses the blood-brain barrier.

Metabolism: Minimal hepatic metabolism.

Excretion: Primarily renally excreted unchanged.

Half Life: Approximately 10-24 hours.

Contraindications

• Hypersensitivity to succinimides or any component of the formulation.

Precautions

• History of hypersensitivity reactions, including rash or Stevens-Johnson syndrome.
• Use with caution in patients with hepatic or renal impairment.
• Monitor for signs of blood dyscrasias, such as leukopenia or anemia.

Adverse Reactions - Common

• Gastrointestinal upset (nausea, vomiting) (Common)
• Drowsiness, dizziness (Common)
• Urinary frequency or urgency (Common)

Adverse Reactions - Serious

• Blood dyscrasias (agranulocytosis, aplastic anemia) (Rare)
• Stevens-Johnson syndrome/Toxic epidermal necrolysis (Rare)
• Severe hypersensitivity reactions (Rare)

Drug-Drug Interactions

• Valproic acid may increase levels of phensuximide.
• Other anticonvulsants may have additive effects.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Take medication exactly as prescribed.
• Do not discontinue abruptly to avoid seizure recurrence.
• Report any signs of skin rash, sore throat, fever, unusual bleeding, or bruising.
• Inform about possible drowsiness and avoid hazardous activities if affected.

Special Considerations

Black Box Warnings:

• Serious dermatologic reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis, have been reported.

Genetic Factors: Genetic variations in drug metabolism may influence response.

Lab Test Interference: May affect liver function tests and blood counts.

Overdose Management

Signs/Symptoms: Drowsiness, vomiting, agitation, coma.

Treatment: Supportive care, activated charcoal if recent ingestion, and monitoring in a healthcare setting.

Storage and Handling

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

Stability: Stable under recommended storage conditions.