Acute epilepsy exacerbations in patients switched between A-rated anti-epileptic drugs

Widespread skeptic attitudes among people with epilepsy toward generic antiseizure drugs - A Swedish survey study

PURPOSE

To explore associations between the characteristics of people with epilepsy (PWE) and their attitudes toward generic substitution of antiseizure drugs (ASDs) in epilepsy.

METHODS

This was a cross-sectional survey study directed at adults with epilepsy using selected brand drugs: Keppra®, Lamictal®, Lyrica® or Topimax®. Symptoms of anxiety and depression, sense of self-efficacy, and beliefs about medicines were assessed. Caregivers were asked to answer for persons with intellectual or communicative difficulties.

RESULTS

The total response rate was 41% (n = 178). Almost half (46%) of subjects stated that they would oppose generic substitution (Gen-NEG) if suggested by their neurologist, while 71% would worry about adverse effects and/or increased seizure frequency after a putative switch. Age ≥50 increased the odds of being Gen-NEG (adjusted OR: 2.20, 95% CI: 1.18-4.11). Negative associations with both Gen-NEG and worriers were found for education level of high-school diploma or above, employment/studies, and prior experience of generic ASD switch. The proportion of worriers was much higher among caregivers (21/22) compared to subjects with epilepsy (106/156).

CONCLUSION

High proportions of PWE express concerns regarding generic substitution of ASDs. The elderly and caregivers seem to express particular concerns. Identifying ways to diminish negative outcomes and worries in connection with a switch is an important future field of research in order to ensure high quality, cost-effective health care for the most vulnerable people in our societies.

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.

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.

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.

Switching generic antiepileptic drug manufacturer not linked to seizures: A case-crossover study

OBJECTIVE

With more antiepileptic drugs (AED) becoming available in generic form, we estimated the risk of seizure-related events associated with refilling generic AEDs and the effect of switching between different manufacturers of the same generic drug.

METHODS

We designed a population-based case-crossover study using the Medicaid Analytic eXtract and a US commercial health insurance database. We identified 83,001 generic AED users who experienced a seizure-related hospital admission or emergency room visit between 2000 and 2013 and assessed whether they received a refill of the same AED from the same manufacturer or a different manufacturer. Patients served as their own controls and conditional logistic regression was used to compare exposure to a refill during the hazard period, defined as days 2-36 preceding the seizure-related event, to exposure during the control period, defined as days 51-85 preceding the seizure-related event.

RESULTS

Generic AED refilling was associated with an 8% increase in the odds of seizure-related events (odds ratio [OR] 1.08; 95% confidence interval [CI] 1.06-1.11). The OR following a switch to a different manufacturer of the same AED was 1.09 (95% CI 1.03-1.15); however, after adjusting for the process of refilling, there was no association between switching and seizure-related hospital visits (OR 1.00; 95% CI 0.94-1.07).

CONCLUSIONS

Among patients on a generic AED, refilling the same AED was associated with an elevated risk of seizure-related event; however, there was no additional risk from switching during that refill to a different manufacturer. Generic AEDs available to US patients, with Food and Drug Administration-validated bioequivalence, appear to be safe clinical choices.

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.

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.

Rational use of generic psychotropic drugs

For economic reasons, the generic substitution of branded medications is common and welcome. These replacements are based on the concept of bioequivalence, which is considered equal to therapeutic equivalence. Regulatory standards for bioequivalence require the 90 % confidence intervals of group averages of pharmacokinetic measures of a generic and the original drug to overlap within ±20 %. However, therapeutic equivalence has been challenged for several psychotropic agents by retrospective studies and case reports. To evaluate the degree of bioequivalence and therapeutic equivalence of branded and generic psychotropic drugs, we performed an electronic search (from database inception until 24 May 2012 and without language restrictions) in PubMed/MEDLINE, Cochrane Library, and Web of Science. Search terms were "(generic) AND (psychotropic OR psychoactive OR antipsychotic OR antiepileptic OR antidepressant OR stimulant OR benzodiazepine)" or the respective individual substances. We included clinical studies, regardless of design, comparing branded with generic psychotropic drug formulations, identifying 35 such studies. We also included case reports/series reporting on outcomes after a switch between brand and generic psychotropics, identifying 145 clinical cases. Bioequivalence studies in healthy controls or animals, in-vitro studies, and health economics studies without medical information were excluded. An overview of the few randomized controlled studies supports that US FDA regulations assure clinically adequate drug delivery in the majority of patients switched from brand to generic. However, with a growing number of competing generic products for one substance, and growing economic pressure to substitute with the currently cheapest generic, frequent generic-generic switches, often unbeknownst to prescribing clinicians, raise concerns, particularly for antiepileptics/mood stabilizers. Generic-generic switches may vary by more than ±20 % from each other in individual patients since the pharmacokinetic properties of each generic may differ from the innovator drug in opposing directions. Ideally, therapeutic equivalence studies in addition to pharmacokinetic equivalence studies would be performed for each generic, reflecting the full variability of clinical responses due to changes of pharmacokinetic properties related to age, sex, ethnicity, genetic factors, and body mass index. This is particularly relevant, as bioequivalence studies are based on single-dose studies in healthy controls who are likely not representative of the patients who are prescribed the psychotropic medications. Additionally, individual case reports suggest potential clinical effects during brand-generic switches. Knowledge and consideration of intra-individual variations can help guide the clinical management during brand-generic or generic-generic switch periods. To optimize outcomes, clinicians need to consider that when using generic psychotropic medications, a change in the patient's clinical status can be related to psychological, interactional, physiological, and pharmacological factors that may or may not be related to the change to a generic drug. In addition, throughout all treatment periods, clinicians need to be aware of the currently dispensed product (i.e., branded or exact generic formulation), particularly when evaluating clinical changes in efficacy, tolerability, and adherence. If clinical problems occur, the first response should be an assessment of adherence and a careful dose adjustments of the generic drug rather than an immediate switch back to the originator.

Generic substitution of antiepileptic drugs: What's a clinician to do?

Generic substitution of antiepileptic drugs remains a controversial area without a clear consensus to guide clinicians. The US Food and Drug Administration (FDA) requires rigorous testing of generic products and states that all approved products are interchangeable. FDA studies involve single doses in normal subjects so may not represent the performance of generic products in people with epilepsy. Physician surveys, case reports, and retrospective pharmacy database analyses suggest that antiepileptic drug generic substitution is associated with more health problems and high switchback rates, but these studies have insufficient detail on seizure control and blood levels. Several ongoing prospective randomized trials with rigorous pharmacokinetic methods aim to provide more data for decision-making.

Near real-time adverse drug reaction surveillance within population-based health networks: methodology considerations for data accrual

PURPOSE

This study describes practical considerations for implementation of near real-time medical product safety surveillance in a distributed health data network.

METHODS

We conducted pilot active safety surveillance comparing generic divalproex sodium to historical branded product at four health plans from April to October 2009. Outcomes reported are all-cause emergency room visits and fractures. One retrospective data extract was completed (January 2002-June 2008), followed by seven prospective monthly extracts (January 2008-November 2009). To evaluate delays in claims processing, we used three analytic approaches: near real-time sequential analysis, sequential analysis with 1.5 month delay, and nonsequential (using final retrospective data). Sequential analyses used the maximized sequential probability ratio test. Procedural and logistical barriers to active surveillance were documented.

RESULTS

We identified 6586 new users of generic divalproex sodium and 43,960 new users of the branded product. Quality control methods identified 16 extract errors, which were corrected. Near real-time extracts captured 87.5% of emergency room visits and 50.0% of fractures, which improved to 98.3% and 68.7% respectively with 1.5 month delay. We did not identify signals for either outcome regardless of extract timeframe, and slight differences in the test statistic and relative risk estimates were found.

CONCLUSIONS

Near real-time sequential safety surveillance is feasible, but several barriers warrant attention. Data quality review of each data extract was necessary. Although signal detection was not affected by delay in analysis, when using a historical control group differential accrual between exposure and outcomes may theoretically bias near real-time risk estimates towards the null, causing failure to detect a signal.

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.

A high-stakes decision: Generic substitution of antiepileptic drugs

In recent years, generic versions of several antiepileptic drugs have been approved and released to the US market. This article reviews some of the concerns associated with generic substitution of antiepileptic drugs.

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.

Efficacy and safety of innovator versus generic drugs in patients with epilepsy: a systematic review

Generic antiepileptic drugs achieve blood concentrations similar to those of innovator drugs in healthy volunteers, but their comparative effectiveness has not been well evaluated. Thus, we assessed the efficacy, tolerability, and safety of innovator versus generic antiepileptic drugs. We searched the MEDLINE database, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Web of Science for studies that evaluated innovator and generic antiepileptic drugs in patients with epilepsy and reported data on prespecified outcomes. We extracted data on study design, interventions, quality criteria, study population, baseline characteristics, and outcomes. Compared with initiation of innovator antiepileptic drugs, initiation of generic antiepileptic drugs did not significantly alter seizure occurrence (relative risk [RR] 0.87, 95% confidence interval [CI] 0.64-1.18; strength of evidence: low) or frequency (standardized mean difference 0.03, 95% CI -0.08-0.14; strength of evidence: low), withdrawals due to lack of efficacy (RR 1.02, 95% CI 0.41-2.54; strength of evidence: low) or adverse events (RR 0.79, 95% CI 0.28-2.20; strength of evidence: low), pharmacokinetic concentrations (maximum, minimum, or area under the curve [strength of evidence: low]), or a myriad of adverse events (strength of evidence: low or insufficient) in clinical trials. In qualitatively evaluated observational studies, switching between forms of antiepileptic drug (innovator to generic, generic to generic) may increase the risk of hospitalization (strength of evidence: low), hospital stay duration (strength of evidence: low), and a composite end point of medical service utilization (strength of evidence: insufficient) but may not increase outpatient service utilization (strength of evidence: low). Data are limited predominantly to carbamazepine, phenytoin, and valproic acid. Clinical trials are limited by small sample size, short-term nature, and lack of specification of A-rated generic products (generics that the United States Food and Drug Administration has deemed bioequivalent to the innovator drug). Observational trials lack full accounting for confounders and have inherent limitations. With a low strength of evidence, it appears that initiating an innovator or generic antiepileptic drug will provide similar efficacy, tolerability, and safety but that switching from one form to the other may be associated with more hospitalizations and longer hospital stays.

Clinical and pharmacy utilization outcomes with brand to generic antiepileptic switches in patients with epilepsy

PURPOSE

To determine if switching from select branded to generic equivalent antiepileptic drugs (AEDs) in patients with epilepsy is associated with adverse outcomes.

METHODS

A retrospective cohort study using a large health insurance plan claims database comparing patients with epilepsy who switched from brand to generic equivalent phenytoin, lamotrigine, or divalproex after 6 months (switch cohorts) to matched patients who remained on the brand (nonswitch cohorts). Primary outcomes measured include the incidence rate ratio (IRR) of discontinuation of the index AED; change in dose of index AED or addition of another AED; and the event rate ratio (ERR) of the composite of all-cause emergency department (ED) visits or hospitalizations.

KEY FINDINGS

Lamotrigine and divalproex showed no differences in AED utilization changes between the switchers and nonswitchers [IRR for lamotrigine 1.00, 95% confidence interval (CI) 0.84-1.19; IRR for divalproex 1.02, 95% CI, 0.88-1.42]. Compared with nonswitchers, the phenytoin switch cohort had greater incidence of AED utilization changes (IRR 1.85, 95% CI 1.50-2.29). The switch versus nonswitch cohorts did not demonstrate differences in ED visits or hospitalizations for the studied AEDs (ERR for phenytoin 0.96, 95% CI 0.80-1.16; ERR for lamotrigine 0.97, 95% CI 0.80-1.17; ERR for divalproex 0.83, 95% CI 0.66-1.06).

SIGNIFICANCE

Brand to generic switching of phenytoin was not associated with more clinical events but was associated with increased index drug discontinuations, dose changes, or therapy augmentations. Lamotrigine or divalproex brand to generic switching was not associated with increased incidence of events or utilization changes compared with patients remaining on the branded product. Changes in AED utilization may be more sensitive than ED visits and hospitalizations for detecting adverse outcomes.

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.

Are generic medications safe and effective?

Because multiple branded, alternative, and generic medications contain the same active ingredient, controversies sometimes arise regarding generic substitution. For patients, physicians, and nurses, the critical issue is whether generic medications are safe and effective. This article addresses the issue with regard to several anti-depressant, anticonvulsant, and antipsychotic medications. There is no consistent evidence that generic substitutes are less safe or effective than brand-name equivalents. Uncontrolled reports are subject to many confounding factors and biases. Relapses temporally associated with medication switches could be due to the change but are difficult to distinguish from the natural history of the treated condition. Adverse effects temporally associated with medication switches could also be attributable to the change, but they might also be explained as a type of "nocebo" effect. Randomized controlled blinded studies are necessary to evaluate causality; however, such studies typically have not supported uncontrolled reports that the safety or effectiveness of brand-name and generic drugs differ. It is still clinically prudent to monitor a patient whose medication has been switched.