Association between antiepileptic drug switching and epilepsy-related events

Association of first anti-seizure medication choice with injuries in older adults with newly diagnosed epilepsy

BACKGROUND

Epilepsy incidence increases exponentially in older adults, who are also at higher risk of adverse drug effects. Anti-seizure medications (ASM) may be associated with sedation and injuries, but discontinuation can result in seizures. We sought to determine whether there was an association between prescribing non-guideline concordant ASM and subsequent injury as this could inform care models.

METHODS

Retrospective cohort study of adults 50 years or older with newly-diagnosed epilepsy in 2015-16, sampled from the MarketScan Databases. The outcome of interest was injury within 1-year of ASM prescription (e.g., burns, falls) and the exposure of interest was ASM category (recommended vs. not recommended by clinical guidelines). Descriptive statistics characterized covariates and a multivariable Cox-regression model was built to examine the association between ASM category and subsequent injury.

RESULTS

5,931 people with newly diagnosed epilepsy were prescribed an ASM within 1-year. The three most common ASMs were: levetiracetam (62.86%), gabapentin (11.73%), and phenytoin (4.45%). Multivariable Cox-regression found that medication category was not associated with injury; however, older age (adjusted hazard ratio (AHR) 1.01/year), history of prior injury (AHR 1.77), traumatic brain injury (AHR 1.55) and ASM polypharmacy (AHR 1.32) were associated with increased hazard of injury.

CONCLUSIONS

Most older adults appear to be getting appropriate first prescriptions for epilepsy. However, a substantial proportion still receives medication that guidelines suggest avoiding. In addition, we show that ASM polypharmacy is associated with an increased hazard of injury within 1- year. Efforts to improve prescribing in older adults with epilepsy should consider how to reduce. both polypharmacy and exposure to medications that guidelines recommend avoiding.

Effects of generic exchange of solid oral dosage forms in neurological disorders: a systematic review

Background Generic drug exchange is common practice in most healthcare systems. While generics certainly contribute to economic savings, the altered drug formulation might be associated with potential therapeutic problems. Given the narrow therapeutic windows in neurologic indications, any detrimental effect on the therapy can lead to significant consequences. Aim of the review This review aims to investigate potential problems related to a switch from brand-name to generic or from generic to generic drug products in patients with neurologic diseases. Method The review was conducted following the PICO framework and the PRISMA guidelines. MEDLINE and Scopus databases were searched for articles published in English and German language between January 1, 1995 and October 17, 2018. Studies included in this review were randomized controlled studies, reviews, systematic reviews, overviews, cohort studies and case-control studies. Studies excluded were letters, comments, authors view, congress or seminar papers and studies with a focus on economic impact or costs. Results were synthesized qualitatively. The primary outcomes were pharmacokinetic parameters such as the area under the curve (AUC), the peak serum concentration (c_max) or the time at which c_max is observed (t_max). Results The search identified 67 studies with a great variety of endpoints and study designs. The leading indication was epilepsy. Two small RCTs were found on lamotrigine switch. Analysis of the other studies found no significant differences in pharmacokinetic parameters when switching to generic drugs. A more heterogeneous picture was revealed regarding hospitalizations, breakthrough seizures, failure of therapy, adherence and patient concerns. Conclusion While most reports were of poor quality, lamotrigine was the drug with the best available data. Summarizing the results of the available studies, pharmacokinetic parameters of antiepileptic drugs show low deviation. In contrast, data on clinical parameters are less consistent. Some studies found increased seizure frequencies and adverse-drug events, while others showed no complications. Adherence and patient satisfaction seemed to be impaired. In daily practice, generic exchange in epilepsy should be a carefully balanced decision, conducted with great caution. Further research is needed, especially regarding neurologic indications other than epilepsy.

Comparative effectiveness of branded vs. generic versions of antihypertensive, lipid-lowering and hypoglycemic substances: a population-wide cohort study

Generic medications offer substantial potential cost savings to health systems compared to their branded counterparts. In Europe and the US, they are only approved if they are bioequivalent to the respective originator product. Nevertheless, the lack of clinical outcomes is sometimes used as the reason for hesitancy in prescribing generics. We performed an observational retrospective study on 17 branded vs. generic pharmaceutical substances for the treatment of hypertension/heart failure, hyperlipidemia, and diabetes mellitus in a dataset of 9,413,620 insured persons, representing nearly the full population of Austria, from 2007 to 2012. We compared generic vs. branded medications using hazard ratios for all-cause death and major adverse cardiac and cardiovascular events (MACCE) as outcomes of interest. Using patient demographics, health characteristics from hospitalization records, and pharmacy records as covariates, we controlled for confounding in Cox models through inverse probability of treatment weighting (IPTW) using high-dimensional propensity scores. We observed that the unadjusted hazard ratios strongly favor generic drugs for all three pooled treatment indications (hypertension/heart failure, hyperlipidemia, diabetes mellitus), but were attenuated towards unity with increasingly larger covariate sets used for confounding control. We found that after IPTW adjustment the generic formulation was associated with significantly fewer deaths in 10 of 17 investigated drugs, and with fewer MACCE in 11 of 17 investigated drugs. This result favoring generic drugs was also present in a number of sub-analyses based on gender, prior disease status, and treatment discontinuation. E-value sensitivity analyses suggested that only strong unmeasured confounding could fully explain away the observed results. In conclusion, generic medications were at least similar, and in some cases superior, to their branded counterparts regarding mortality and major cardiovascular events.

Patterns of seizure prophylaxis after oncologic neurosurgery

BACKGROUND

Evidence supporting routine postoperative antiepileptic drug (AED) prophylaxis following oncologic neurosurgery is limited, and actual practice patterns are largely unknown beyond survey data.

OBJECTIVE

To describe patterns and predictors of postoperative AED prophylaxis following intracranial tumor surgery.

METHODS

The MarketScan Database was used to analyze pharmacy claims data and clinical characteristics in a national sample over a 5-year period.

RESULTS

Among 5895 patients in the cohort, levetiracetam was the most widely used AED for prophylaxis (78.5%) followed by phenytoin (20.5%). Prophylaxis was common but highly variable for patients who underwent open resection of supratentorial intraparenchymal tumors (62.5%, reference) or meningiomas (61.9%). In multivariate analysis, biopsies were less likely to receive prophylaxis (44.8%, OR 0.47, 95% CI 0.33-0.67), and there was near consensus against prophylaxis for infratentorial (9.7%, OR 0.07, CI 0.05-0.09) and transsphenoidal procedures (0.4%, OR 0.003, CI 0.001-0.010). Primary malignancies (52.1%, reference) and secondary metastases (42.2%) were more likely to receive prophylaxis than benign tumors (23.0%, OR 0.63, CI 0.48-0.83), as were patients discharged with home services and patients in the Northeast. There was a large spike in duration of AED use at approximately 30 days.

CONCLUSIONS

Use of seizure prophylaxis following intracranial biopsies and supratentorial resections is highly variable, consistent with a lack of guidelines or consensus. Current practice patterns do not support a clear standard of care and may be driven in part by geographic variation, availability of post-discharge services, and electronic prescribing defaults rather than evidence. Given uncertainty regarding effectiveness, indications, and appropriate duration of AED prophylaxis, well-powered trials are needed.

New-onset lesional and nonlesional epilepsy in the US population: Patient characteristics and patterns of antiepileptic drug use

PURPOSE

Describe treatment patterns in patients from the United States with new-onset epilepsy, comparing those with and without lesional epilepsy.

METHODS

In this observational study we used Truven Health MarketScan databases derived from commercial health insurance, Medicare and Medicaid claims covering at least 5 years, commencing in 2008. We identified incident epilepsy cases based on International Classification of Diseases, Ninth Revision, Clinical Modification codes indicating epilepsy or recurrent seizures, taking into account antiepileptic drug (AED) claims, consistent with International League Against Epilepsy Commission on Epidemiology recommendations. We identified patients with lesional epilepsy when associated diagnoses indicated central nervous system infection, neoplasm, traumatic brain injury, stroke, senile dementia and static encephalopathy. Lesional and nonlesional cohorts were matched 1:1 on baseline characteristics of age, sex and insurance type for group comparisons.

RESULTS

In unmatched cohorts lesional epilepsy patients (N = 15,302) were more commonly older (mean age 48.7 years) compared with nonlesional epilepsy patients (N = 15,970; mean age 18.5 years). Among lesional patients <20 years of age, the leading putative etiology was static encephalopathy, while among ages ≥20 years and older, the leading putative etiology was stroke or cerebrovascular disease. In matched cohorts (7063 patients each), those with lesional epilepsy were significantly less likely to be untreated at 1 year versus those with nonlesional epilepsy (37.2% vs 56.1%). In children and adults among matched cohorts, levetiracetam was the most common AED prescribed for initial AED therapy for the lesional (39.5%) and nonlesional (32.1%) groups. Lesional epilepsy patients on monotherapy were only slightly less likely than nonlesional epilepsy patients to be on the same AED 1 year after treatment initiation (55.6% vs 59.7%).

SIGNIFICANCE

Compared with patients with lesional epilepsy, a higher proportion of patients with nonlesional epilepsy remain untreated 1 year after diagnosis. There were differences in AED selection by epilepsy etiology; levetiracetam is the most commonly prescribed drug for both cohorts.

Generic antiepileptic drugs-Safe or harmful in patients with epilepsy?

Generic antiepileptic drugs (AED) are significantly cheaper than brand name drugs, and may reduce overall health care expenditures. Regulatory bodies in Europe and North America require bioequivalence between generic and innovator drugs with regard to area under the plasma concentration-time curve (AUC) and peak plasma concentration (C_max ); strict cutoff values have been defined. The main issue is if bioequivalence ensures therapeutic equivalence. Are switches from brand to generic, or between generic AEDs entirely safe or potentially harmful in patients with epilepsy? We summarized and evaluated the available evidence from bioequivalence, health care utilization, and clinical studies on safety of generic AEDs. In most cases, variations in AUC and C_max were negligible when comparing innovator and generic AEDs. Due to interindividual pharmacokinetic and pharmacodynamic variability, measured differences between innovator and generic drugs may be the same as differences between different lots of the same brand. Studies from several countries based on insurance data have reported an increase in health care usage after switch from brand to generic AEDs; switchback rates are significantly higher for AEDs compared to other compounds. Patients may be confused, and nonadherence may increase, when AEDs are switched between manufacturers, perhaps due to changes in medication shape and color. But clinical studies do not report changes in seizure frequency and tolerability attributable to generics. Sufficient evidence indicates that most generics are bioequivalent to innovator AEDs; they do not pose a relevant risk for patients with epilepsy. However, some patients are reluctant towards variations in color and shape of their AEDs which may result in nonadherence. We recommend administering generics when a new AED is initiated. Switches from brand to generic AEDs for cost reduction and between generics, which is rarely required, generally seem to be safe, but should be accompanied by thorough counseling of patients on low risks.

Studies on drug switchability showed heterogeneity in methodological approaches: a scoping review

BACKGROUND AND OBJECTIVE

Several drugs share the same therapeutic indication, including those undergoing patent expiration. Concerns on the interchangeability are frequent in clinical practice, challenging the evaluation of switchability through observational research. The objective of this study was to conduct a scoping review of observational studies on drug switchability to identify methodological strategies adopted to deal with bias and confounding.

METHODS

We searched PubMed, EMBASE, and Web of Science (updated January 31, 2017) to identify studies evaluating switchability in terms of effectiveness/safety outcomes or compliance. Three reviewers independently screened studies extracting all characteristics. Strategies to address confounding, particularly previous drug use and switching reasons, were considered. All findings were summarized in descriptive analyses.

RESULTS

Thirty-two studies, published in the last 10 years, met the inclusion criteria. Epilepsy, cardiovascular, and rheumatology were the most frequently represented clinical areas. Seventy-five percent of the studies reported data on effectiveness/safety outcomes. The most frequent study design was cohort (65.6%) followed by case-control (21.9%) and self-controlled (12.5%). Case-control and case-crossover studies showed homogeneous methodological strategies to deal with bias and confounding. Among cohort studies, the confounding associated with previous drug use was addressed introducing variables in multivariate model (47.3%) or selecting only adherent patients (14.3%). Around 30% of cohort studies did not report reasons for switching. In the remaining 70%, clinical parameters or previous occurrence of outcomes was measured to identify switching connected with lack of effectiveness or adverse events.

CONCLUSION

This study represents a starting point for researchers and administrators who are approaching the investigation and assessment of issues related to interchangeability of drugs.

Attention-deficit/hyperactivity disorder medication and seizures

OBJECTIVE

Individuals with attention-deficit/hyperactivity disorder (ADHD) are at increased risk of seizures, but there is uncertainty about whether ADHD medication treatment increases risk among patients with and without preexisting seizures.

METHODS

We followed a sample of 801,838 patients with ADHD who had prescribed drug claims from the Truven Health MarketScan Commercial Claims and Encounters databases to examine whether ADHD medication increases the likelihood of seizures among ADHD patients with and without a history of seizures. First, we assessed overall risk of seizures among patients with ADHD. Second, within-individual concurrent analyses assessed odds of seizure events during months when a patient with ADHD received ADHD medication compared with when the same individual did not, while adjusting for antiepileptic medications. Third, within-individual long-term analyses examined odds of seizure events in relation to the duration of months over the previous 2 years patients received medication.

RESULTS

Patients with ADHD were at higher odds for any seizure compared with non-ADHD controls (odds ratio [OR] = 2.33, 95% confidence interval [CI] = 2.24-2.42 males; OR = 2.31, 95% CI = 2.22-2.42 females). In adjusted within-individual comparisons, ADHD medication was associated with lower odds of seizures among patients with (OR = 0.71, 95% CI = 0.60-0.85) and without (OR = 0.71, 95% CI = 0.62-0.82) prior seizures. Long-term within-individual comparisons suggested no evidence of an association between medication use and seizures among individuals with (OR = 0.87, 95% CI = 0.59-1.30) and without (OR = 1.01, 95% CI = 0.80-1.28) a seizure history.

CONCLUSIONS

Results reaffirm that patients with ADHD are at higher risk of seizures. However, ADHD medication was associated with lower risk of seizures within individuals while they were dispensed medication, which is not consistent with the hypothesis that ADHD medication increases risk of seizures.

Association between switching antiepileptic drug products and healthcare utilization: A systematic review

AIMS

There is ongoing concern whether switching between different antiepileptic drug (AED) products may compromise patient care. We systematically reviewed changes in healthcare utilization following AED switch.

METHODS

We searched MEDLINE and EMBASE databases (1980-October 2016) for studies that assessed the effect of AED switching in patients with epilepsy on outpatient visits, emergency room visits, hospitalization and hospital stay duration.

RESULTS

A total of 14 articles met the inclusion criteria. All were retrospective studies. Four provided findings for specific AEDs only (lamotrigine, topiramate, phenytoin and divalproex), 9 presented pooled findings from multiple AEDs, and 1 study provided both specific (lamotrigine, topiramate, oxcarbazepine, and levetiracetam) and pooled findings. Three studies found an association between a switch of topiramate and an increase in healthcare utilization. Another three studies found that a brand-to-generic lamotrigine switch was not associated with an increased risk of emergently treated events (ambulance use, ER visits or hospitalization). The outcomes of the pooled AED switch studies were inconsistent; 5 studies reported an increased healthcare utilization while 5 studies did not.

CONCLUSION

Studies that have examined the association between an AED switch and a change in healthcare utilization report conflicting findings. Factors that may explain these inconsistent outcomes include inter-study differences in the type of analysis undertaken (pooled vs individual AED data), the covariates used for data adjustment, and the type of switch examined. Future medical claim database studies employing a prospective design are encouraged to address these and other factors in order to enhance inter-study comparability and extrapolation of findings.

Comparative effectiveness of generic versus brand-name antiepileptic medications

OBJECTIVE

The objective of this study was to compare treatment persistence and rates of seizure-related events in patients who initiate antiepileptic drug (AED) therapy with a generic versus a brand-name product.

METHODS

We used linked electronic medical and pharmacy claims data to identify Medicare beneficiaries who initiated one of five AEDs (clonazepam, gabapentin, oxcarbazepine, phenytoin, zonisamide). We matched initiators of generic versus brand-name versions of these drugs using a propensity score that accounted for demographic, clinical, and health service utilization variables. We used a Cox proportional hazards model to compare rates of seizure-related emergency room (ER) visit or hospitalization (primary outcome) and ER visit for bone fracture or head injury (secondary outcome) between the matched generic and brand-name initiators. We also compared treatment persistence, measured as time to first 14-day treatment gap, between generic and brand-name initiators.

RESULTS

We identified 19,760 AED initiators who met study eligibility criteria; 18,306 (93%) initiated a generic AED. In the matched cohort, we observed 47 seizure-related hospitalizations and ER visits among brand-name initiators and 31 events among generic initiators, corresponding to a hazard ratio of 0.53 (95% confidence interval, 0.30 to 0.96). Similar results were observed for the secondary clinical endpoint and across sensitivity analyses. Mean time to first treatment gap was 124.2 days (standard deviation [sd], 125.8) for brand-name initiators and 137.9 (sd, 148.6) for generic initiators.

SIGNIFICANCE

Patients who initiated generic AEDs had fewer adverse seizure-related clinical outcomes and longer continuous treatment periods before experiencing a gap than those who initiated brand-name versions.

Factors associated with seizure recurrence in epilepsy patients treated with antiepileptic monotherapy: A retrospective observational cohort study using US administrative insurance claims

BACKGROUND

Few studies examine predictors of seizures in medically treated patients with epilepsy receiving antiepileptic monotherapy using a large patient population.

OBJECTIVE

Our objective was to identify clinical, medication, and demographic factors associated with seizure recurrence in medically treated patients with epilepsy receiving one of four antiepileptic monotherapy regimens: lamotrigine, levetiracetam, oxcarbazepine, or topiramate.

STUDY DESIGN

A retrospective cohort study was conducted using Innovus Invision™ Data Mart paid medical and prescription US commercial insurance claims data from January 2007 to September 2010.

METHODS

Patients aged 18-64 years with a primary or secondary diagnosis of epilepsy and one or more prescription claim for an antiepileptic drug (AED) pre-index were included. The primary outcome was incidence of a seizure or seizure-related event, defined as an emergency room visit, ambulance service use, or inpatient hospitalization medical claim with a primary or secondary diagnosis of epilepsy during the 1-year follow-up. The factors included AED adherence, somatic comorbidity (measured via Charlson Comorbidity Index), mental health comorbidity, pre-index seizure, type of epilepsy diagnosis, presence of AED-interacting medications and any bioequivalent AED switch. The covariates included age, gender, and geographic region of residence.

RESULTS

A total of 5.3 % (166/3,140) of patients on AED monotherapy had experienced a seizure or a seizure-related event requiring urgent care at 1-year follow-up. The multivariate analysis of the combined cohort showed that pre-index seizures/seizure-related events (odds ratio [OR] 4.23; 95 % confidence interval [CI] 2.77-6.46), any mental health comorbidity (OR 3.50; 95 % CI 2.14-5.70), and Charlson Comorbidity Index ≥1 (OR 2.91; 95 % CI 1.98-4.28) were significantly associated with post-index seizures/seizure-related events. Patients residing in Northeastern USA had a higher likelihood of a post-index seizure (OR 1.90; 95 % CI 1.17-3.08) than patients residing in the Southern region of the USA. Bioequivalent AED switch, type of epilepsy diagnosis, AED adherence, and presence of AED-interacting medications were not associated with seizure recurrence in the combined cohort analysis (p > 0.05).

CONCLUSIONS

Epilepsy patients with comorbid conditions (both mental and somatic diseases) and prior seizures were more likely to experience seizures at 1-year follow-up. Non-adherent patients and patients with bioequivalent AED switches appeared to show no increased likelihood of seizure at follow-up. Clinicians may consider these findings before starting or transitioning to an AED monotherapy.

Topiramate use does not reduce flares of inflammatory bowel disease

BACKGROUND

Additional medications are needed for inflammatory bowel disease (IBD) as existing therapies are incompletely effective and can be costly and toxic. Preclinical studies suggest that topiramate (an anticonvulsant) may have disease-modifying properties in IBD, but its efficacy in humans is unknown.

AIM

To evaluate whether topiramate use is associated with clinical benefit in IBD patients.

METHODS

We conducted a retrospective cohort study using administrative claims data from the MarketScan databases. Persons with IBD were identified between 2000 and 2010. New users of topiramate were compared with users of other anticonvulsant and anti-migraine medications. The primary outcome was a new prescription for an oral steroid (≥14 days). Secondary outcomes included initiation of biologic agents, abdominal surgery, and hospitalization. Cox proportional hazard modeling was used to adjust for potential confounders.

RESULTS

We identified 773 new users of topiramate and 958 users of comparator drugs. After adjusting for potential confounders, topiramate use was not associated with the primary outcome of steroid prescriptions [hazard ratio (HR) 1.14, 95 % confidence interval (CI) 0.74, 1.73]. Results did not differ significantly by IBD subtype. There was no difference between topiramate users and users of comparator drugs with respect to post-exposure initiation of biologic agents (HR 0.93, 95 % CI 0.39, 2.19), abdominal surgery (HR 1.04, 95 % CI 0.17, 6.41), or hospitalization (HR 0.86, 95 % CI 0.62, 1.19).

CONCLUSION

In this large U.S. administrative claims study, topiramate use was not associated with markers of IBD flares. These results cast doubt on whether topiramate may be an effective adjunct to current IBD therapy.

Is switching from brand name to generic formulations of phenobarbital associated with loss of antiepileptic efficacy?: a pharmacokinetic study with two oral formulations (Luminal(®) vet, Phenoleptil(®)) in dogs

Background

In human medicine, adverse outcomes associated with switching between bioequivalent brand name and generic antiepileptic drug products is a subject of concern among clinicians. In veterinary medicine, epilepsy in dogs is usually treated with phenobarbital, either with the standard brand name formulation Luminal® or the veterinary products Luminal® vet and the generic formulation Phenoleptil®. Luminal® and Luminal® vet are identical 100 mg tablet formulations, while Phenoleptil® is available in the form of 12.5 and 50 mg tablets. Following approval of Phenoleptil® for treatment of canine epilepsy, it was repeatedly reported by clinicians and dog owners that switching from Luminal® (human tablets) to Phenoleptil® in epileptic dogs, which were controlled by treatment with Luminal®, induced recurrence of seizures. In the present study, we compared bioavailability of phenobarbital after single dose administration of Luminal® vet vs. Phenoleptil® with a crossover design in 8 healthy Beagle dogs. Both drugs were administered at a dose of 100 mg/dog, resulting in 8 mg/kg phenobarbital on average.

Results

Peak plasma concentrations (C_max) following Luminal® vet vs. Phenoleptil® were about the same in most dogs (10.9 ± 0.92 vs. 10.5 ± 0.77 μg/ml), and only one dog showed noticeable lower concentrations after Phenoleptil® vs. Luminal® vet. Elimination half-life was about 50 h (50.3 ± 3.1 vs. 52.9 ± 2.8 h) without differences between the formulations. The relative bioavailability of the two products (Phenoleptil® vs. Luminal® vet.) was 0.98 ± 0.031, indicating that both formulations resulted in about the same bioavailability.

Conclusions

Overall, the two formulations did not differ significantly with respect to pharmacokinetic parameters when mean group parameters were compared. Thus, the reasons for the anecdotal reports, if true, that switching from the brand to the generic formulation of phenobarbital may lead to recurrence of seizures are obviously not related to a generally lower bioavailability of the generic formulation, although single dogs may exhibit lower plasma levels after the generic formulation that could be clinically meaningful.

Bioequivalent antiepileptic drug switching and the risk of seizure-related events

BACKGROUND

Older antiepileptic drugs (AEDs) are known to have a narrow therapeutic index. As a consequence, switching between bioequivalent AEDs remains controversial in the management of epilepsy. We investigated the association between A-rated switching of each class of currently available AED and emergent treatment for a seizure-related event.

METHODS

We used a case-control method and claims data from the 2010 to 2011 Truven Health MarketScan(®) Commercial Claims Database to estimate the risk of seizure following a medication switch. Cases and controls with an epilepsy diagnosis were identified by emergency/inpatient or outpatient visit claims, respectively. Cases and controls (N=9110) were matched 1:1 by age, epilepsy diagnosis category and seizure medication. The exposure was defined as a switch between A-rated AEDs during the 90 days prior to index date. Conditional logistic regression was used to estimate the association, adjusting for gender, baseline Deyo-Charlson Comorbidity Index (0, 1, 2, or 3+), region (Northeast, Central, South, and West), and total AED medications.

RESULTS

A switch between A-rated AEDs occurred in 1053 (23.2%) cases and 827 (18.1%) matched controls. The unadjusted and adjusted odds ratios of a seizure-related event for switching were 1.38 (95% CI: 1.25-1.52) and 1.27 (95% CI: 1.14-1.41), respectively. The independent risk of an event also increased with each category increase in the Charlson score (CCI=1: 1.17, 95% CI: 1.02-1.33; CCI=2: 1.33, 95% CI: 1.09-1.62; CCI=3+: 1.99, 95% CI: 1.64-2.41). Older AEDs had infrequent switches compared to newer agents and were not associated with events.

DISCUSSION

We found a modest association between AED switching and seizure-related events. Our analysis suggests that the behavior of switching alone may lead to seizure-related events regardless of the medication or type of switch. Other disease or environmental characteristics may contribute to this association. Based on these and other findings, health care professionals and patients should be cautious about switching bioequivalent AEDs.

Economic differences in direct and indirect costs between people with epilepsy and without epilepsy

OBJECTIVE

To provide generalizable estimates of economic burden in epilepsy and nonepilepsy populations and a comprehensive accounting for employment-based lost productivity associated with epilepsy in current US health care systems as compared with other chronic diseases.

RESEARCH DESIGN

We use the nationally representative data source (Medical Expenditure Panel Survey) from 1998 to 2009 to create a retrospective cohort of people diagnosed with epilepsy by a health professional and a comparison cohort of people with no epilepsy.

MEASURES

Health care utilization and direct costs for all components of treatment, including prescription medications, wages, employment, educational attainment, family income, and lost productivity were outcomes.

RESULTS

We observed economic disparities associated with epilepsy in the United States despite high rates of modern treatments (89% on anticonvulsant therapies). Only 42% of the people with epilepsy over age 18 reported employment compared with 70% of people with no epilepsy; among those, people with epilepsy reported missing an average of 12 days of work because of illness or injury as compared with 4 days in the nonepilepsy cohort. Holding other variables constant, people with epilepsy had a loss of productivity of $9504 in 2011 dollars compared with people with no epilepsy. In comparison, diabetes was associated with annual average lost productivity valued at $3358 and depression at $3182.

CONCLUSIONS

Lost wage-based productivity associated with epilepsy was nearly equal to combined wage losses associated with diabetes, depression, anxiety, and asthma together. To evaluate societal burden of illness, results illustrate the importance of indirect costs in addition to treated prevalence and direct medical costs.

Generic antiepileptic drug prescribing: a cross-sectional study

The use of generic antiepileptic drugs (AEDs) in patients with epilepsy is controversial. The purpose of this study is to identify patient characteristics associated with increased odds of receiving a generic AED product. A large commercial database was used to identify patients with a primary diagnosis of epilepsy who were prescribed an AED during a three-month window. Data analysis found that those ≥65 years old had 15.7% greater odds of receiving a generic AED (OR = 1.157; 95% CI = 1.056-1.268). Patients with Medicaid were found to have 2.44 times the odds of having had a generic AED prescription (OR = 2.44; CI = 2.168-2.754). Patients residing in the Northeast had 12.6% decreased odds of receiving a generic AED (OR = 0.874; C I= 0.821-0.931). These patient characteristics could signify certain health care disparities and may represent potential confounders to future observational studies.

Generic substitution of lamotrigine among medicaid patients with diverse indications: a cohort-crossover study

BACKGROUND

Controversy exists about the safety of substituting generic antiepileptic drugs (AEDs). Lamotrigine, the prototypical newer AED, is often used for psychiatric and neurological conditions other than epilepsy. The safety of generic substitution of lamotrigine in diverse populations of AED users is unclear.

OBJECTIVE

The objective of this study was to evaluate potential associations between generic substitution of lamotrigine and adverse consequences in a population of diverse users of this drug.

STUDY DESIGN

This study was a retrospective cohort-crossover design using state Medicaid claims data from July 2006 through June 2009.

METHODS

Subjects were included in the cohort if they converted from brand to generic lamotrigine and had 2 years of lamotrigine use prior to conversion. The frequency of emergency department (ED) visits, hospitalizations and condition-specific ED visits or hospitalizations were recorded in the 60 days immediately following the conversion to generic lamotrigine, then compared with the incidence of the same events during a randomly selected time period indexed to one of the patient's past refills of branded lamotrigine. Multivariate conditional logistic regression was used to quantify the association between generic conversion and health services utilization while controlling for changes in lamotrigine dose and concurrent drug use.

RESULTS

Of the 616 unique subjects included in this analysis, epilepsy was the most common diagnosis (41%), followed by bipolar disorder (32%), pain (30%) and migraine (18%). Conversion to generic lamotrigine was not associated with a statistically significant increase in the odds of an ED visit (adjusted odds ratio [AOR] = 1.35; 95% confidence interval [CI] 0.92, 1.97), hospitalization (AOR = 1.21; 95% CI 0.60, 2.50) or condition-specific encounter (AOR 1.75; 95 CI 0.87, 3.51).

CONCLUSIONS

A statistically significant increase in ED visits, hospitalizations or condition-specific encounters was not observed following the switch from brand to generic lamotrigine, although a type II error cannot be ruled out.

Host factors affecting antiepileptic drug delivery-pharmacokinetic variability

Antiepileptic drugs (AEDs) are the mainstay in the treatment of epilepsy, one of the most common serious chronic neurological disorders. AEDs display extensive pharmacological variability between and within patients, and a major determinant of differences in response to treatment is pharmacokinetic variability. Host factors affecting AED delivery may be defined as the pharmacokinetic characteristics that determine the AED delivery to the site of action, the epileptic focus. Individual differences may occur in absorption, distribution, metabolism and excretion. These differences can be determined by genetic factors including gender and ethnicity, but the pharmacokinetics of AEDs can also be affected by age, specific physiological states in life, such as pregnancy, or pathological conditions including hepatic and renal insufficiency. Pharmacokinetic interactions with other drugs are another important source of variability in response to AEDs. Pharmacokinetic characteristics of the presently available AEDs are discussed in this review as well as their clinical implications.

Clinical outcomes associated with brand-to-generic phenytoin interchange

BACKGROUND

Concerns that antiepileptic brand-to-generic interchange results in disruption of seizure control are widespread. However, little within-patient evidence exists examining such interchanges.

OBJECTIVE

To compare within-patient seizure control before and after the interchange of a branded to a single-source generic phenytoin among patients with seizures in a managed care organization.

METHODS

This was a pre-post, self-controlled, retrospective study. Adults with a history of seizure who used Dilantin Kapseals 100 mg extended phenytoin sodium, USP, capsules and whose therapy was interchanged to Taro Pharmaceuticals' AB-rated generic extended phenytoin sodium capsules, USP, 100 mg between July 2007 and May 2008 were included. Study outcomes included the comparisons of the proportions of patients with at least emergency department (ED) visit/inpatient hospitalization and medical office visit/nonoffice consultation for acute seizure in the 6 months before and after interchange. Outcomes were confirmed with manual chart reviews and adjusted for potential confounding medication use.

RESULTS

A total of 222 patients were included in the study. Patients were primarily middle-aged (mean 56 years), equally mixed by sex (47% female); most had nonintractable seizures. The majority of patients (~70%) were on phenytoin as monotherapy and had equivalent rates of purchases for potentially confounding medications in both pre- and postinterchange time periods (all p > 0.05). Low serum concentrations were detected more often in the postinterchange study period (adjusted p < 0.001). Despite this, there were low proportions of patients with confirmed seizure events that resulted in an ED visit/inpatient hospitalization in both pre- and postinterchange periods (both 6.3%, adjusted p = 0.937). The proportion of patients with confirmed seizure events diagnosed at a medical office visit was not significantly different between the preinterchange and postinterchange periods (12.2% vs 11.3%, adjusted p = 0.545).

CONCLUSIONS

No increased proportion of seizures was observed within patients when branded phenytoin was interchanged to an AB-rated, single-source, generic equivalent. More rigorous studies should be conducted to more thoroughly evaluate patient tolerability and drug efficacy when antiepileptic drugs are interchanged from brand to generic formulations.

Crossover studies with survival outcomes

Crossover designs are well known to have major advantages when comparing the effect of two treatments which do not interact. With a right-censored survival endpoint, however, this design is quickly abandoned in favour of the more costly parallel design. Motivated by human immunodeficiency virus (HIV) prevention studies which lacked power, we evaluate what may be gained in this setting and compare parallel with crossover designs. In a heterogeneous population, we find and explain a substantial increase in power for the crossover study using a non-parametric logrank test. With frailties in a proportional hazards model, crossover designs equally lead to substantially smaller variance for the subject-specific hazard ratio (HR), while the population-averaged HR sees negligible gain. Its efficiency benefit is recovered when the population-averaged HR is reconstructed from estimated subject-specific hazard rates. We derive the time point for treatment crossover that optimizes efficiency and end with the analysis of two recent HIV prevention trials. We find that a Cellulose sulphate trial could have hardly gained efficiency from a crossover design, while a Nonoxynol-9 trial stood to gain substantial power. We conclude that there is a role for effective crossover designs in important classes of survival problems.

Exploring community pharmacists' views on generic medicines: a nationwide study from Malaysia

OBJECTIVE

To evaluate the Malaysian community pharmacists' views on generic medicines.

SETTING

A sample of 1419 Malaysian community pharmacies with resident pharmacists.

METHOD

A cross-sectional nationwide survey using a self-completed mailing questionnaire.

MAIN OUTCOME MEASURE

Pharmacists' views on generic medicines including issues surrounding efficacy, safety, quality and bioequivalence.

RESULTS

Responses were received from 219 pharmacies (response rate 15.4%). Only 50.2% of the surveyed pharmacists agreed that all products that are approved as generic equivalents can be considered therapeutically equivalent with the innovator medicines. Around 76% of respondents indicated that generic substitution of narrow therapeutic index medicines is inappropriate. The majority of the pharmacists understood that a generic medicine must contain the same amount of active ingredient (84.5%) and must be in the same dosage form as the innovator brand (71.7%). About 21% of respondents though that generic medicines are of inferior quality compared to innovator medicines. Most of the pharmacists (61.6%) disagreed that generic medicines produce more side-effects than innovator brand. Pharmacists graduated from Malaysian universities, twinning program and overseas universities were not differed significantly in their views on generic medicines. Additionally, the respondents appeared to have difficulty in ascertaining the bioequivalent status of the marketed generic products in Malaysia.

CONCLUSION

The Malaysian pharmacists' have lack of information and/or trust in the generic manufacturing and/or approval system in Malaysia. This issue should be addressed by pharmacy educators and relevant government agencies.

Refilling and switching of antiepileptic drugs and seizure-related events

We sought to estimate the risk of seizure-related events associated with refilling prescriptions for antiepileptic drugs (AEDs) and to estimate the effect of switching between brand-name and generic drugs or between two generic versions of the same drug. We conducted a case-crossover study using health-care databases from British Columbia, Canada, among AED users who had an emergency room visit or hospitalization for seizure (index seizure-related event), defined using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9) codes 345.xx (epilepsy and recurrent seizures) and 780.3x (convulsions), between 1997 and 2005. AED prescription refilling itself was associated with 2.3-fold elevated odds of seizure-related events when the refill occurred within 21 days before the index event (odds ratio (OR) 2.31; 95% confidence interval (CI) 1.56-3.44). The OR was 2.75 (95% CI 0.88-8.64) for refills that involved switching, yielding a refill-adjusted OR for switching of 1.19 (95% CI 0.35-3.99). Refilling the same AED prescription was associated with an elevated risk of seizure-related events whether or not the refill involved switching from a brand-name to a generic product.

Economic burden associated with the use of generic antiepileptic drugs in the United States

This study quantifies the economic burden associated with generic-versus-branded use of antiepileptic drugs (AEDs) in the United States. Adult patients with epilepsy receiving carbamazepine, gabapentin, phenytoin, primidone, or zonisamide were selected from the PharMetrics database. By use of an open-cohort design, patients were classified into mutually exclusive periods of generic-versus-branded AED use. Annualized cost differences (CDs) between periods were estimated using multivariate regressions. Results were stratified into stable versus unstable epilepsy and newer-generation versus older-generation AEDs. A total of 33,625 patients (52% male, mean age=51 years) were observed. Periods of generic AED treatment were associated with higher medical service costs (adjusted CD [95% CI]=$3186 [$2359; $4012]), stable pharmacy costs ($69 [$-34; $171]), and greater total costs ($3254 [$2403; $4105]) versus brand use. Epilepsy-related costs represented 30% of incremental costs. Similar findings were observed for patients with stable and unstable epilepsy and users of newer-generation and older-generation AEDs. Significantly higher health care costs were observed during generic AED use across seizure control and AED subgroups.

Seizure outcomes following the use of generic versus brand-name antiepileptic drugs: a systematic review and meta-analysis

The automatic substitution of bioequivalent generics for brand-name antiepileptic drugs (AEDs) has been linked by anecdotal reports to loss of seizure control. To evaluate studies comparing brand-name and generic AEDs, and determine whether evidence exists of superiority of the brand-name version in maintaining seizure control. English-language human studies identified in searches of MEDLINE, EMBASE and International Pharmaceutical Abstracts (1984 to 2009). Randomized controlled trials (RCTs) and observational studies comparing seizure events or seizure-related outcomes between one brand-name AED and at least one alternative version produced by a distinct manufacturer. We identified 16 articles (9 RCTs, 1 prospective nonrandomized trial, 6 observational studies). We assessed characteristics of the studies and, for RCTs, extracted counts for patients whose seizures were characterized as 'controlled' and 'uncontrolled'. Seven RCTs were included in the meta-analysis. The aggregate odds ratio (n = 204) was 1.1 (95% CI 0.9, 1.2), indicating no difference in the odds of uncontrolled seizure for patients on generic medications compared with patients on brand-name medications. In contrast, the observational studies identified trends in drug or health services utilization that the authors attributed to changes in seizure control. Although most RCTs were short-term evaluations, the available evidence does not suggest an association between loss of seizure control and generic substitution of at least three types of AEDs. The observational study data may be explained by factors such as undue concern from patients or physicians about the effectiveness of generic AEDs after a recent switch. In the absence of better data, physicians may want to consider more intensive monitoring of high-risk patients taking AEDs when any switch occurs.

Direct medical costs for patients seeking emergency care for losses of epilepsy control in a U.S. managed care setting

The objective of this retrospective claims database study was to compare the costs of care from a U.S. payer perspective before and after epilepsy treatment in emergent care settings and, secondarily, to describe the frequency of toxic effects and physical injuries occurring on the date of the emergent care. Nine and four-tenths percent of patients receiving emergent care for epilepsy (114/1213) had an injury or adverse antiepileptic drug effect on the same date. The majority of incidents were superficial injuries and contusions (28%), fractures (21%), open wounds or injury to blood vessels (19%), intracranial injury (10%), and/or medication toxicity (10%). Both non-epilepsy-related (US$12,745.56) and epilepsy-related (US$2013.62) direct medical costs of care pre-index were significantly different from those post-index (US$15,274.95 and US$7087.53, respectively). The cost of care for possible reestablishment of epilepsy control and treatment of co-occurring injuries is significant when compared with that for the period prior to seizure.