Vigabatrin

Vigabatrin was developed by Lundbeck Pharmaceuticals and was approved for market by the US Food and Drug Administration (FDA) in August 2009.

Vigabatrin is mainly used for the treatment of epilepsy in infants and adults, especially as a therapeutic drug for infantile spasms.

Vigabatrin is a gamma aminobutyric acid metabolism inhibitor mainly used to treat refractory partial epileptic seizures, especially suitable for refractory childhood epileptic seizures.

1.Main components

Vigabatrin

2.Adapt to the population

Vigabatrin is an adjuvant therapy for refractory complex partial epilepsy patients aged 2 years and above.

3.Medication for special populations

3.1Pregnancy

There are no adequate data on the developmental risk associated with the use of Vigabatrin in pregnant women. Limited available data from case reports and cohort studies pertaining to Vigabatrin use in pregnant women have not established a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. However, based on animal data, Vigabatrin use in pregnant women may result in fetal harm. 

3.2Lactation

Vigabatrin is excreted in human milk. The effects of Vigabatrin on the breastfed infant and on milk production are unknown. Because of the potential for serious adverse reactions from vigabatrin in nursing infants, breastfeeding is not recommended. If exposing a breastfed infant to Vigabatrin, observe for any potential adverse effects.

3.3Pediatric Use

The safety and effectiveness of Vigabatrin as adjunctive treatment of refractory complex partial seizures in pediatric patients 2 to 16 years of age have been established and is supported by three double-blind, placebo-controlled studies in patients 3 to16 years of age,  adequate and well-controlled studies in adult patients, pharmacokinetic data from patients 2 years of age and older, and additional safety information in patients 2 years of age. The dosing recommendation in this population varies according to age group and is weight-based. Adverse  reactions in this pediatric population are similar to those observed in the adult population. The safety and effectiveness of Vigabatrin as monotherapy for pediatric patients with infantile spasms (1 month to 2 years of age) have been established.

Safety and effectiveness as adjunctive treatment of refractory complex partial seizures in pediatric patients below the age of 2 and as monotherapy for the treatment of infantile spasms in pediatric patients below the age of 1 month have not been established.

Duration of therapy for infantile spasms was evaluated in a post hoc analysis of a Canadian Pediatric Epilepsy Network (CPEN) study of developmental outcomes in infantile spasms patients. This analysis suggests that a total duration of 6 months of vigabatrin therapy is adequate for the treatment of infantile spasms. However, prescribers must use their clinical judgment as to the most appropriate duration of use.

Abnormal MRI signal changes and Intramyelinic Edema (IME) in infants and young children being treated with Vigabatrin have been observed.

3.4Geriatric Use

Vigabatrin is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.  

Oral administration of a single dose of 1.5g of vigabatrin to elderly (≥65 years) patients with reduced creatinine clearance (<50 mL/min) was associated with moderate to severe sedation and confusion in 4 of 5 patients, lasting up to 5 days. The renal clearance of vigabatrin was 36% lower in healthy elderly subjects (≥65 years) than in young healthy males. Adjustment of dose or  frequency of administration should be considered. Such patients may respond to a lower maintenance dose.

Other reported clinical experience has not identified differences in responses between the elderly and younger patients. 

3.5Renal Impairment

Dose adjustment, including initiating treatment with a lower dose, is necessary in pediatric patients 2 years of age and older and adults  with mild (creatinine clearance >50 to 80 mL/min), moderate (creatinine clearance >30 to 50 mL/min) and severe (creatinine  clearance >10 to 30 mL/min) renal impairment.

4.Drug overdose

4.1Signs, Symptoms, and Laboratory Findings of Overdosage

Confirmed and/or suspected vigabatrin overdoses have been reported during clinical trials and in post marketing surveillance. No vigabatrin overdoses resulted in death. When reported, the vigabatrin dose ingested ranged from 3g to 90g, but most were between 7.5g and 30g. Nearly half the cases involved multiple drug ingestions including carbamazepine, barbiturates, benzodiazepines,  lamotrigine, valproic acid, acetaminophen, and/or chlorpheniramine.

Coma, unconsciousness, and/or drowsiness were described in the majority of cases of vigabatrin overdose. Other less commonly  reported symptoms included vertigo, psychosis, apnea or respiratory depression, bradycardia, agitation, irritability, confusion,  headache, hypotension, abnormal behavior, increased seizure activity, status epilepticus, and speech disorder. These symptoms  resolved with supportive care.

4.2Management of Overdosage

There is no specific antidote for Vigabatrin overdose. Standard measures to remove unabsorbed drug should be used, including elimination by emesis or gastric lavage. Supportive measures should be employed, including monitoring of vital signs and observation of the clinical status of the patient.  

In an in vitro study, activated charcoal did not significantly adsorb vigabatrin.

The effectiveness of hemodialysis in the treatment of Vigabatrin overdose is unknown. In isolated case reports in renal failure patients  receiving therapeutic doses of vigabatrin, hemodialysis reduced vigabatrin plasma concentrations by 40% to 60%.

5.Drug storage

Store at 20°C to 25°C (68°F to 77°F). See USP controlled room temperature.

6.Pharmacokinetics

Following oral administration, vigabatrin is essentially completely absorbed. The time to maximum concentration (Tmax) is  approximately 1 hour for children and adolescents (3 years to 16 years of age) and adults, and approximately 2.5 hours for infants (5  months to 2 years of age). There was little accumulation with multiple dosing in adult and pediatric patients. A food effect study  involving administration of vigabatrin to healthy volunteers under fasting and fed conditions indicated that the Cmax was decreased by 33%, Tmax was increased to 2 hours, and AUC was unchanged under fed conditions.

from FDA，2021.10