Child: As monotherapy: Initially: 25 mg/kg bid; may adjust in increments of 25-50 mg/kg daily every 3 days, according to clinical response and tolerability. Max: 150 mg/kg daily.
Oral Refractory complex partial seizures, Resistant partial epilepsy with or without secondary generalisation
Adult: In cases where alternative treatments are inadequate or intolerable: As adjunctive therapy: Initially, 1 g daily as a single or in 2 divided doses; adjust dose in increments of 0.5 g weekly, according to clinical response and tolerability. Max: 3 g daily. Child: In cases where alternative treatments are inadequate or intolerable: As adjunctive therapy: Initially, 40 mg/kg daily as a single or in 2 divided doses. Maintenance: 10-15 kg: 0.5-1 g daily; 15-30 kg: 1-1.5 g daily; 30-50 kg: 1.5-3 g daily; >50 kg: 2-3 g daily. Dosing recommendations may vary among countries or individual products or preparations. Refer to country- or product-specific recommendations. Elderly: Initiate at the lower end of the dosing range.
Renal Impairment
Resistant partial epilepsy with or without secondary generalisation; Refractory complex partial seizures:
CrCl (mL/min)
Dosage
>10-30
Decrease dose by 75%.
>30-50
Decrease dose by 50%.
>50-80
Decrease dose by 25%.
Administration
May be taken with or without food.
Special Precautions
Patient with history of psychosis, depression or behavioural problems; myoclonic seizures. Not indicated as 1st-line agent for complex partial seizures. Not recommended in patients with pre-existing visual field defects. Avoid abrupt withdrawal. Renal impairment. Children and elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Visual field defects, risk for permanent vision loss, anaemia, CNS depression, oedema, peripheral neuropathy, suicidal ideation and behaviour, weight gain. Eye disorders: Blurred vision, diplopia, nystagmus. Gastrointestinal disorders: Abdominal pain, nausea, vomiting. General disorders and administration site conditions: Fatigue, irritability. Musculoskeletal and connective tissue disorders: Arthralgia. Nervous system disorders: Somnolence, headache, dizziness, paraesthesia, tremor. Psychiatric disorders: Agitation, aggression, nervousness, depression, paranoid reaction, insomnia, disturbance in attention and memory impairment. Skin and subcutaneous tissue disorders: Alopecia.
PO: Z (Insufficient data to conclude its safety and risk during pregnancy. Use only when benefits outweigh risks.)
Patient Counseling Information
This drug may cause drowsiness or visual field defects, if affected, do not drive or operate machinery.
Monitoring Parameters
Perform ophthalmologic examination (e.g. dilated indirect ophthalmoscopy of the retina, visual acuity, visual field) at baseline (no later than 4 weeks after initiation), periodically (every 3 months) during therapy, and 3-6 months after discontinuation of therapy. Monitor Hb, haematocrit, weight gain, oedema; signs of visual defect, neurotoxicity, peripheral neuropathy, fluid retention. Observe for clinical worsening, suicidality, or unusual changes in behaviour and excessive sedation.
May decrease ALT and AST levels. May increase level of amino acids in urine leading to false-positive test for rare genetic metabolic disorder.
Action
Description: Vigabatrin is a selective irreversible inhibitor of gamma-aminobutyric acid transaminase (GABA-T), resulting in increased levels of the major inhibitory neurotransmitter gamma-aminobutyric acid (GABA) within the brain. Duration: Variable (dependent on the rate of GABA-T resynthesis). Pharmacokinetics: Absorption: Rapidly and completely absorbed from the gastrointestinal tract. Time to peak plasma concentration: Approx 1 hour. Distribution: Widely distributed. Crosses the placenta and enters breast milk. Volume of distribution: 1.1 L/kg. Excretion: Via urine (approx 80%, as unchanged drug). Terminal elimination half-life: Approx 10.5 hours.
Chemical Structure
Vigabatrin Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 5665, Vigabatrin. https://pubchem.ncbi.nlm.nih.gov/compound/Vigabatrin. Accessed Oct. 26, 2021.
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