Evaluating risks for vigabatrin treatment

Trends and Costs Associated With the Diagnosis and Treatment of Infantile Spasms: A 10-Year Multicenter Retrospective Review

OBJECTIVE

Early treatment of infantile spasms (IS) may be imperative for improvement of neurodevelopmental outcomes. Existing studies have led to inconclusive recommendations with variation in treatment. Our objective was to determine the national average cost, initial diagnostic workup, treatments, and hospital length of stay for patients with IS.

METHODS

This retrospective cohort study was designed to review data of patients < 2 years from 43 non-profit institutions. Data obtained included patient demographics, length of stay, admission cost, and treatments used from 2004 to 2014. Cost data were collected and adjusted to 2014 dollars, the year data were analyzed.

RESULTS

A total of 6183 patients met study criteria (n = 3382, 55% male). Three-quarters of patients (n = 4684, 76%) had an electroencephalogram, 56.4% had brain imaging (n = 3487), and 17% (n = 1050) underwent a lumbar puncture. Medication for IS was initiated during inpatient hospital stay in two-thirds of all patients (n = 4139, 67%). Most patients were initiated on corticotropin (n = 2066, 33%) or topiramate (n = 1804, 29%). Average length of stay was 5.8 days with an average adjusted cost of $18,348. Over time there was an 86.6% increase in cost from an average $12,534.54 (2004) to $23,391.20 (2014), a significant change (p < 0.01). This correlated with an increase in average length of stay.

CONCLUSIONS

Variability exists in diagnostic workup and pharmacotherapy initiated for IS, which may lead to differences in the cost of hospital stay. Further studies may help determine contributing factors to increased cost and improve health care utilization for IS patients.

Metabolism and Functions of Amino Acids in Sense Organs

Sense organs (eyes, ears, nose, tongue, and skin) provide senses of sight, hearing, smell, taste, and touch, respectively, to aid the survival, development, learning, and adaptation of humans and other animals (including fish). Amino acids (AAs) play an important role in the growth, development, and functions of the sense organs. Recent work has identified receptor-mediated mechanisms responsible for the chemosensory transduction of five basic taste qualities (sweet, sour, bitter, umami and salty tastes). Abnormal metabolism of AAs result in a structural deformity of tissues and their dysfunction. To date, there is a large database for AA metabolism in the eye and skin under normal (e.g., developmental changes and physiological responses) and pathological (e.g., nutritional and metabolic diseases, nutrient deficiency, infections, and cancer) conditions. Important metabolites of AAs include nitric oxide and polyamines (from arginine), melanin and dopamine (from phenylalanine and tyrosine), and serotonin and melatonin (from tryptophan) in both the eye and the skin; γ-aminobutyrate (from glutamate) in the retina; and urocanic acid and histamine (from histidine) in the skin. At present, relatively little is known about the synthesis or catabolism of AAs in the ears, nose, and tongue. Future research should be directed to: (1) address this issue with regard to healthy ageing, nasal and sinus cancer, the regulation of food intake, and oral cavity health; and (2) understand how prenatal and postnatal nutrition and environmental pollution affect the growth, development and health of the sense organs, as well as their expression of genes (including epigenetics) and proteins in humans and other animals.

Efficacy and safety of vigabatrin in Japanese patients with infantile spasms: Primary short-term study and extension study

Vigabatrin was approved for the treatment of infantile spasms by the US Food and Drug Administration, but not in Japan at the time of initiating this clinical study because of concerns about irreversible peripheral visual field defects (VFDs). This study evaluated the efficacy and safety of vigabatrin for Japanese patients with infantile spasms. Of 15 patients (aged ≥4weeks and <2years) enrolled, with the exception of two patients who did not receive vigabatrin, 13 were treated with a titrated dosage of vigabatrin (50-150mg/kg/day; limited to 3000mg/day). Twelve out of 13 patients receiving vigabatrin had spasms that were treatment refractory; these patients were concurrently treated with at least one other antiepileptic drug. One patient received vigabatrin monotherapy. Eight of the 13 patients (61.5% [95% CI: 31.6-86.1%]) had a ≥50% reduction during the dose-adjustment phase compared with baseline in the frequency of spasms, with efficacy maintained through a 2-week maintenance phase. Spasms disappeared in six out of nine patients (66.7% [95% CI: 29.9-92.5%]) who transitioned to the maintenance phase and hypsarrhythmia on electroencephalography also resolved in four patients. Hypsarrhythmia was improved in another two patients. Six out of seven patients who continued treatment through Week 32 of an extension study reported ongoing efficacy for vigabatrin. The most common adverse events (AEs) were psychiatric disorders and nervous system disorders (n=8; 61.5%) that were generally mild in severity. No treatment-related peripheral VFDs were observed. No severe AEs or AEs resulting in discontinuation of vigabatrin therapy were reported. An abnormality in magnetic resonance images was observed in one patient during the extension period. Vigabatrin was deemed to be clinically effective and well tolerated in Japanese patients with infantile spasms.

VIGABATRIN TOXICITY IN INFANCY IS ASSOCIATED WITH RETINAL DEFECT IN ADOLESCENCE: A Prospective Observational Study

PURPOSE

The purpose was to determine whether vigabatrin (VGB) (Sabril)-attributed retinal toxicity defined by electroretinogram in early childhood is associated with visual system defect in adolescents after discontinuation of VGB.

METHODS

This prospective cross-sectional study included 24 children previously treated with VGB and monitored in early childhood by electroretinogram for VGB-attributed retinal defects. Ten had been diagnosed with VGB-attributed retinal defect (Group I) and 14 had no VGB-attributed retinal defect (Group II). Outcome measures were extent of monocular visual fields using Goldmann kinetic perimetry and RNFL thickness at the optic nerve head, using optical coherence tomography.

RESULTS

Of those able to complete testing (6 eyes Group I and 16 eyes Group II), Goldmann results revealed results of visual field loss in Group I and not in Group II. The optical coherence tomography results demonstrated attenuation of the RNFL in all 6 eyes of Group I participants and in only 1 eye of 10 Group II participants. Optical coherence tomography data were nonoverlapping between Group 1 and Group II eyes.

CONCLUSION

The VGB-attributed retinal toxicity identified by means of electroretinogram in infancy was associated with visual field loss and RNFL attenuation of the retinal nerve when tested in adolescence.

Reduction of retinal nerve fiber layer thickness in vigabatrin-exposed patients: A meta-analysis

OBJECTIVE

Vigabatrin (VGB) is currently served as an effective adjunctive therapy for patients with partial epilepsy worldwide. In this study, meta-analysis was conducted to comprehensively evaluate the changes in peripapillary retinal nerve fiber layer (RNFL) thickness assessed by optical coherence tomography (OCT) in epilepsy patients who were treated by VGB.

MATERIAL AND METHODS

Publications on PubMed, Wiley Online Library and the Elsevier Science databases were searched by September 2016. The statistical analysis was performed by RevMan 5.3 software.

RESULTS

Four studies were identified, and 202 eyes in VGB-exposed patients (VGB group) as well as 162 eyes in patients who never received VGB treatment (NON-VGB group) were included. The studies demonstrated that the total RNFL thickness is attenuated in VGB treated patients (weighted mean differences in μm, WMD=-15.96, 95% CI: -23.69 to -8.23, P<0.0001). RNFL thickness in 3 quadrants were significantly reduced in VGB group: superior (WMD=-18.15, 95% CI: -23.31 to -12.98, P<0.00001), inferior (WMD=-23.19, 95% CI: -32.23 to -14.15, P<0.00001) and nasal (WMD=-19.29, 95% CI: -35.57 to -3.02, P=0.02). However, the temporal RNFL thickness in these two groups showed no significant difference: temporal (WMD=-2.41, 95% CI: -6.67 to 1.85, P=0.27).

CONCLUSION

Based on the meta-analysis, RNFL thickness appears to reduce in epilepsy patients who received VGB treatment, and OCT could be a useful tool to help clinicians assessing its retinal toxicity and guiding its dosage.

Sabril® registry 5-year results: Characteristics of adult patients treated with vigabatrin

Vigabatrin (Sabril®), approved in the US in 2009, is currently indicated as adjunctive therapy for refractory complex partial seizures (rCPS) in patients ≥ 10 years old who have responded inadequately to several alternative treatments and as monotherapy for infantile spasms (IS) in patients 1 month to 2 years of age. Because of reports of vision loss following vigabatrin exposure, FDA approval required a risk evaluation mitigation strategy (REMS) program. Vigabatrin is only available in the US through Support, Help, And Resources for Epilepsy (SHARE), which includes a mandated registry. This article describes 5 years of demographic and treatment exposure data from adult patients (≥ 17 years old) in the US treated with vigabatrin and monitored in the ongoing Sabril® registry. Registry participation is mandatory for all US Sabril® prescribers and patients. A benefit-risk assessment must be documented by the physician for a patient to progress to maintenance therapy, defined as 1 month of vigabatrin treatment for patients with IS and 3 months for patients with rCPS. Ophthalmologic assessments must be documented during and after completion of therapy. As of August 26, 2014, a total of 6823 patients were enrolled in the registry, of which 1200 were adults at enrollment. Of these patients, 1031 (86%) were naïve to vigabatrin. The majority of adult patients (n=783, 65%) had previously been prescribed ≥ 4 AEDs, and 719 (60%) were receiving ≥ 3 concomitant AEDs at vigabatrin initiation. Prescribers submitted an initial ophthalmological assessment form for 863 patients; an ophthalmologic exam was not completed for 300 (35%) patients and thus, were considered exempted from vision testing. Of these patients, 128 (43%) were exempted for neurologic disabilities. Clinicians discontinued treatment in 8 patients because of visual field deficits (VFD) (5 patients naïve to vigabatrin and 3 patients previously exposed). Based on Kaplan-Meier survival estimates, it is estimated that approximately 71%, 55%, and 40% of adult patients naïve to vigabatrin would remain in the registry at 3, 6, and 12 months, respectively. These demographic data suggest that a proportion of adult patients remain on vigabatrin long-term despite the risks of adverse events and significant underlying AED resistance and neurologic disease.

Newer anti-epileptic drugs

NEED AND PURPOSE OF REVIEW

A number of newer anti-epileptic drugs have been developed in the last few years to improve the treatment outcomes in epilepsy. In this review, we discuss the use of newer anti-epileptic drugs in children.

METHODS USED FOR LOCATING, SELECTING, EXTRACTING AND SYNTHESIZING DATA

MEDLINE search (1966-2013) was performed using terms newer anti-epileptic drugs, Oxcarbazepine, vigabatrin, topiramate, zonisamide, levetiracetam, lacosamide, rufinamide, stiripentol, retigabine, eslicarbazepine, brivaracetam, ganaxolone and perampanel for reports on use in children. Review articles, practice parameters, guidelines, systematic reviews, meta-analyses, randomized controlled trials, cohort studies, and case series were included. The main data extracted included indications, efficacy and adverse effects in children.

MAIN CONCLUSIONS

Oxcarbazepine is established as effective initial monotherapy for children with partial-onset seizures. Vigabatrin is the drug of choice for infantile spasms associated with tuberous sclerosis. Lamotrigine, levetiracetam and lacosamide are good add-on drugs for patients with partial seizures. Lamotrigine may be considered as monotherapy in adolescent females with idiopathic generalized epilepsy. Levetiracetam is a good option as monotherapy for females with juvenile myoclonic epilepsy. Topiramate is a good add-on drug in patients with epileptic encephalopathies such as Lennox-Gastaut syndrome and myoclonic astatic epilepsy.

Monitoring the cognitive effects of antiepileptic pharmacotherapy--approaching the individual patient

Cognitive side effects of antiepileptic drugs are common and can negatively affect tolerability, compliance, and long-term retention of the treatment. Furthermore, adverse cognitive effects of pharmacotherapy significantly affect everyday functioning and quality of life. Consequently, preservation of cognitive functions is an important aspect of epilepsy therapy. Knowledge of the patient's neuropsychological status before and after pharmacological interventions can help to decide on the appropriate treatment and, thus, can potentially improve individual medical care. Here, we suggest that cognitive monitoring of antiepileptic pharmacotherapy--like the assessment of seizure frequency, blood serum levels, electroencephalography or structural imaging--should be carried out as a matter of routine. In contrast to subjective measures, there are only very few neuropsychological instruments explicitly validated for the assessment of cognition along with antiepileptic pharmacotherapy. This review (1.) outlines indications and requirements for individual cognitive monitoring, (2.) discusses available diagnostic tools, and (3.) discloses relevant pitfalls. Neuropsychology, as demonstrated, provides evidence-based methods for monitoring cognitive effects of individual pharmacological treatments and, therefore, serves as a valuable tool for the quality and outcome control of antiepileptic therapies.

Understanding and interpreting vision safety issues with vigabatrin therapy

Vigabatrin is an irreversible inhibitor of γ-aminobutyric acid (GABA) transaminase. It is effective as adjunctive therapy for adult patients with refractory complex partial seizures (rCPS) who have inadequately responded to several alternative treatments and as monotherapy for children aged 1 month to 2 years with infantile spasms. The well-documented safety profile of vigabatrin includes risk of retinopathy characterized by irreversible, bilateral, concentric peripheral visual field constriction. Thus, monitoring of visual function to understand the occurrence and manage the potential consequences of peripheral visual field defects (pVFDs) is now required for all patients who receive vigabatrin. However, screening for pVFDs for patients with epilepsy was conducted only after the association between vigabatrin and pVFDs was established. We examined the potential association between pVFDs and epilepsy in vigabatrin-naïve patients and attempted to identify confounding factors (e.g., concomitant medications, method of vision assessment) to more accurately delineate the prevalence of pVFDs directly associated with vigabatrin. Results of a prospective cohort study as well as several case series and case reports suggest that bilateral visual field constriction is not restricted to patients exposed to vigabatrin but has also been detected, although much less frequently, in vigabatrin-naïve patients with epilepsy, including those who received treatment with other GABAergic antiepileptic therapy. We also reviewed published data suggesting an association between vigabatrin-associated retinal toxicity and taurine deficiency, as well as the potential role of taurine in the prevention of this retinopathy.

New drugs for pediatric epilepsy

The last 2 decades have witnessed an unprecedented period of new antiepileptic drug (AED) development. Newer-generation AEDs have been developed with the intention of improving the ease of use, decreasing drug interactions, decreasing adverse side effects, and identifying drugs with unique mechanisms of action, some of which may bear relevance to potential neuroprotective activity. Drug trials have also been refined in some cases to evaluate AED efficacy in children and against distinct epilepsy syndromes. This progress provides many new treatment options for the child neurologist facing children with epilepsy but also introduces the burden of determining appropriate AED choices. Here we highlight 6 new antiepileptic medications recently approved or pending approval for use in the United States: lacosamide, rufinamide, vigabatrin, retigabine, brivaracetam, and clobazam. For each of these medications, we present information regarding the history of drug development, proposed mechanism(s) of action, pharmacokinetics and recommended dosing, evidence for clinical efficacy, tolerability, and when, available, any unique features that are relevant for the pediatric population.