SABRIL 500/MG FC TAB 100/FC TAB

Indications

Approved Uses

1) Refractory complex partial seizures (adjunctive therapy) in adults and pediatric patients ≥2 years; 2) Infantile spasms (monotherapy) in infants 1 month to 2 years.

Off-Label Uses

Seizures associated with succinic semialdehyde dehydrogenase deficiency (SSADHD) (off-label).

Dosage & Administration

Dosing by Condition

Refractory complex partial seizures (≥2 years, adjunctive): Adults start 500 mg twice daily (1000 mg/day) and increase by 500 mg/day at weekly intervals; usual maintenance 3000 mg/day (1500 mg twice daily), max 3000 mg/day. Infantile spasms (1 month-2 years, monotherapy): start 50 mg/kg/day (25 mg/kg twice daily

Initial Dose

Adults (Refractory Complex Partial Seizures): 1000 mg/day (500 mg twice daily).

Maintenance Dose

Adults (Refractory Complex Partial Seizures): 3000 mg/day (1500 mg twice daily).

Maximum Dose

Adults (Refractory Complex Partial Seizures): 3000 mg/day is recommended, though doses up to 6000 mg/day have been used. Infants (Infantile Spasms): 150 mg/kg/day.

Dose Adjustment Notes

Dose reduction is required in renal impairment; avoid abrupt discontinuation-taper when stopping; discontinue if inadequate benefit (generally within ~3 months for refractory complex partial seizures and within ~2-4 weeks for infantile spasms).

How to Take

Oral use; may be taken with or without food; swallow tablets with water. If unable to swallow tablets, use the oral-solution formulation (where available) rather than crushing/chewing tablets.

Side Effects

Common Side Effects

Somnolence/drowsiness, fatigue, dizziness, headache, weight gain, tremor, blurred vision/visual disturbance, abnormal coordination/ataxia, nausea.

Safety & Warnings

Warnings & Precautions

Key warnings/precautions: irreversible vision loss-baseline and periodic vision assessment and restricted access/REMS; discontinue if inadequate benefit; suicidal thoughts/behavior; CNS depression/somnolence; MRI abnormalities in infants; taper to discontinue; adjust dose in renal impairment; weight gain/edema and peripheral neuropathy may occur.

Age Restriction

Refractory complex partial (focal) seizures: adults (US labeling

Drug Interactions

Food Interaction

No clinically significant food restriction; may be taken with or without food.

Special Populations

Elderly

Start at lower end of dosing range; titrate slowly; monitor renal function and adjust dose accordingly due to age-related decline in renal clearance

Kidney Impairment

Dose reduction required in renal impairment: CrCl 50-80 mL/min reduce ~25%; CrCl 30-50 reduce ~50%; CrCl 10-30 reduce ~75%; CrCl <10 mL/min or dialysis: use extreme caution with substantial reduction and close monitoring.

Liver Impairment

No hepatic dose adjustment recommended.

Storage & Patient Advice

Stopping the Medicine

Do not stop abruptly; taper gradually (individualized-typically over at least 2-4 weeks when feasible) to reduce risk of increased seizures/status epilepticus.

Patient Counseling

Counsel on risk of permanent vision loss/visual field constriction: baseline eye assessment and periodic monitoring (commonly about every 3 months during therapy and after discontinuation per local program/label); report any vision changes immediately. Do not stop abruptly (seizure risk). May cause somnolence/dizziness-avoid driving/machinery until effects known; avoid alcohol/other CNS depressants. Report mood/behavior changes or suicidal ideation. Take exactly as prescribed at consistent times; dose adjustments are needed in renal impairment.

Monitoring Requirements

Vision monitoring: baseline ophthalmologic assessment (including visual field testing when feasible), then at least every 3 months during therapy and again about 3-6 months after discontinuation; monitor renal function and clinical response/adverse CNS effects.

Pharmacology

Mechanism of Action

Irreversibly inhibits GABA-transaminase (GABA-T), reducing GABA breakdown and increasing CNS GABA concentrations, thereby decreasing neuronal excitability.

Duration of Effect

Pharmacodynamic effect outlasts plasma half-life because GABA-T inhibition is irreversible; recovery depends on enzyme resynthesis over several days after discontinuation.

Half-Life

Plasma half-life is about 5-8 hours in adults; it is prolonged in renal impairment and may be longer in older adults, while pharmacodynamic effect can outlast plasma levels due to irreversible enzyme inhibition.

Bioavailability

High oral bioavailability, approximately 60-80% (often cited ~70%).

Metabolism

Not significantly metabolized; minimal hepatic metabolism and not meaningfully CYP-mediated.

Excretion

Primarily renal elimination; the majority is excreted unchanged in urine (commonly ~70% within 24 hours, with most of the dose recovered unchanged over time).

Protein Binding

Negligible protein binding (approximately 0%).

Product Information

Available Dosage Forms

Film-coated tablet; powder for oral solution (oral formulation availability may be market-specific).

Composition per Dose

Each film-coated tablet: 500mg vigabatrin

Generic Availability

Yes

OTC Alternatives

No OTC alternative

Psych Class

Antiepileptic

Controlled Substance

No

Reviewed by Al Mujtama Pharmacy Medical Review Team. Last reviewed 11-06-2026