Weigeding Vigabatrin Powder for Oral Solution

1. Indications and Usage
Infantile Spasms (IS): Indicated as monotherapy for infantile spasms in children 1 month to 21 years of age when the potential benefit outweighs the potential risk of vision loss.
Complex Partial Seizures (CPS): Indicated as adjunctive therapy for adult patients (17 years and older) who have had an inadequate response to multiple antiepileptic drugs.
2. Dosage and Administration
Infantile Spasms: The initial dose is 50 mg/kg/day, divided into two doses. The dose may be increased by 25-150 mg/kg/day every 3 days to a maximum of 150 mg/kg/day.
Complex Partial Seizures: The initial dose is 500 mg twice daily. The dose may be increased by 500 mg/day weekly to a maximum recommended dose of 3 g/day (1.5 g twice daily).
Administration: The powder for oral solution should be dissolved in 10 mL of cold or room temperature water per packet. It can be taken with or without food.
Renal Impairment: Dose reductions are required for patients with mild to moderate renal impairment.
Discontinuation: The dose should be tapered gradually to avoid withdrawal seizures.
3. Mechanism of Action
GABA-T Inhibition: Vigabatrin is a structural analogue of GABA that irreversibly inhibits the enzyme GABA transaminase (GABA-T).
GABA Elevation: By inhibiting GABA-T, it prevents the degradation of gamma-aminobutyric acid (GABA), leading to increased concentrations of GABA in the brain. This enhances inhibitory neurotransmission and suppresses neuronal hyperexcitability.
4. Safety and Warnings
Vision Loss: Can cause permanent bilateral concentric visual field constriction. Baseline and periodic ophthalmologic monitoring is mandatory.
MRI Abnormalities: May cause reversible, asymptomatic T1-weighted MRI signal changes in the brain.
Suicidal Behavior and Ideation: Antiepileptic drugs increase the risk of suicidal thoughts and behavior.
SEDATION: May cause somnolence and fatigue; patients should exercise caution when driving or operating machinery.
SHARE Program: Due to the risk of permanent vision loss, distribution is restricted to a special access program (SHARE).
5. Adverse Reactions and Clinical Research
Adverse Reactions: Common adverse reactions include somnolence, upper respiratory tract infection, fever, and weight gain.
Clinical Research: Clinical trials have demonstrated significant reduction in infantile spasms and complex partial seizures compared to placebo.
6. Drug Interactions
Phenytoin: Vigabatrin may decrease plasma phenytoin levels by approximately 16-20%.
Other CNS Depressants: Concomitant use with other antiepileptic drugs (e.g., phenobarbital, valproate) may enhance sedative effects.
Ophthalmologic Toxicity: Contraindicated with other drugs known to cause retinopathy or glaucoma unless the benefit clearly outweighs the risk.
7. Pharmaceutical Information
Composition: The active ingredient is vigabatrin (as powder for oral solution).
Appearance: Typically supplied as white to off-white powder packets.
Storage: Store at controlled room temperature and protect from moisture.