What are the precautions for Vigabatrin?

In clinical studies of Vigabatrin (Vigabatrin), warnings and precautions such as permanent vision loss, infant MRI abnormalities, neurotoxicity, suicidal behavior and thoughts, discontinuation of anti-epileptic drugs, anemia, lethargy and fatigue, peripheral neuropathy, weight gain, edema, etc. have occurred. Discontinue the drug and resume at a reduced dose upon recovery, or permanently discontinue Vigabatrin based on severity.

1.Permanent vision loss: Vigabatrin can cause permanent blindness. Based on adult studies, 30% or more of patients may be affected by bilateral concentric visual field constriction, ranging in severity from mild to severe. Severe cases may be characterized by tunnel vision within 10 degrees of visual fixation, which may lead to disability. In some cases, Vigabatrin can also damage the central retina and may reduce vision. Patients or caregivers are unlikely to recognize the symptoms of vision loss caused by Vigabatrin until the vision loss is severe. The possibility that vigabatrin-induced vision loss is more common, more severe, or has more serious functional consequences in infants and children than in adults cannot be excluded.

Vigabatrin-induced vision loss is unpredictable and may occur within weeks of starting treatment or earlier, or any time after starting treatment, even months or years later. In patients with refractory complex partial epilepsy, Vigabatrin should be discontinued if no substantial clinical benefit is observed within 3 months of starting treatment. If, in the prescriber's clinical judgment, evidence of treatment failure became apparent before 3 months, treatment should be discontinued at that time. In patients with infantile spasms, Vigabatrin should be discontinued if no significant clinical benefit is observed within 2 to 4 weeks. If, in the prescriber's clinical judgment, evidence of treatment failure becomes apparent before 2-4 weeks, treatment should be discontinued at this time.

2. Infant magnetic resonance imaging (MRI) abnormalities: Abnormal MRI signal changes have been observed in some infants treated with Vigabatrin, characterized by increased T2 signal with restricted diffusion in a symmetrical pattern involving the thalamus, basal ganglia, brainstem, and cerebellum. Routine MRI monitoring is not necessary for adults receiving vigabatrin as there is no evidence that vigabatrin causes MRI changes in this population.

3. Neurotoxicity: Intramyelin edema (IME) has been reported at autopsy in infants treated with vigabatrin for infantile spasms. Abnormal MRI signal changes, characterized by increased T2 signal with restricted diffusion in a symmetrical pattern involving the thalamus, basal ganglia, brainstem, and cerebellum, have also been observed in some infants treated with Vigabatrin. In animal studies, administration to female rats during gestation and lactation at doses lower than those used clinically resulted in hippocampal vacuolation and twitching in adult offspring.

4. Suicidal Behavior and Thoughts: Antiepileptic drugs (AEDs), including Vigabatrin, increase the risk of suicidal thoughts or behaviors in patients taking these drugs for any indication. Patients receiving any AED should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior. Patients, their caregivers, and families should be informed that AEDs increase the risk of suicidal thoughts and behaviors and that patients should be alerted to the emergence or worsening of signs and symptoms of depression, any unusual changes in mood or behavior, or the emergence of suicidal thoughts, behaviors, or thoughts of self-harm. Behavior of concern should be reported to the doctor immediately.

5. Discontinue anti-epileptic drugs: Like allAEDs, Vigabatrin should be withdrawn gradually. However, if discontinuation is necessary due to serious adverse events, rapid discontinuation may be considered. Patients and caregivers should be advised not to discontinue treatment with Vigabatrin suddenly. In controlled clinical studies in adults with complex partial epilepsy, Vibatrin was tapered by reducing the daily dose by 1000 mg/day weekly until discontinued. In a controlled study in pediatric patients with complex partial epilepsy, vigabatrin was tapered by reducing the daily dose by one-third each week for three weeks. In a controlled clinical study in patients with infantile spasms, Vibatrin was tapered by reducing the daily dose at a rate of 25-50 mg/kg every 3-4 days.

6. Anemia: The adverse event of anemia occurs and/or meets the criteria for potentially clinically important hematological changes (including hemoglobin, hematocrit and/or red blood cell index). In controlled and open-label epilepsy trials in adult and pediatric patients, a rare minority of patients experienced unexplained drops in hemoglobin below 8 g/dL and/or hematocrit below 24%.

7. Drowsiness and fatigue: Patients should be advised not to drive a car or operate other complex machinery until they are familiar with the effects of Vigabatrin on their ability to perform such activities.

8. Peripheral neuropathy: In these trials, initial signs of peripheral neuropathy include, in some combinations, symptoms of numbness or tingling in the toes or feet, signs of diminished vibration or position sense in the distal lower extremity, or progressive loss of reflexes starting at the ankle. Clinical studies in development programs are not designed to systematically study peripheral neuropathy and do not include nerve conduction studies, quantitative sensory testing, or skin or nerve biopsies. There is insufficient evidence to determine whether the development of these signs and symptoms is related to the duration of vigabatrin treatment, the cumulative dose, or whether the findings of peripheral neuropathy are fully reversible after cessation of vigabatrin.

9. Weight gain: Across all epilepsy trials, 0.6% of Vigabatrin patients discontinued the drug due to weight gain. The long-term effects of vigabatrin-related weight gain are unknown. Weight gain is not associated with the development of edema.

Edema: Pediatric clinical trials were not designed to assess edema, but the pooled edema-based data observed in controlled pediatric studies appear to be similar in pediatric patients taking Vigabatrin and placebo. In these studies, one Vibatrin patient and no placebo patient discontinued due to edema-related adverse events. In adults, there is no clear association between edema and adverse cardiovascular events such as hypertension or congestive heart failure. Edema is not associated with laboratory changes suggestive of worsening renal or hepatic function.