Case-control analysis of ambulance, emergency room, or inpatient hospital events for epilepsy and antiepileptic drug formulation changes

Prescribing generic antiepileptic drugs: Issues and concerns for nurse practitioners

PURPOSE

To educate prescribing clinicians about bioequivalent standards for therapeutic equivalence of brand and generic antiepileptic drugs (AEDs) as more generic drugs come to market, and to increase awareness of practice and safety issues surrounding the use of these drugs for people with seizures.

DATA SOURCES

Information was gathered from a search of the scientific literature as well as the author's clinical experience.

CONCLUSIONS

Controversy exists regarding the therapeutic equivalence of brand and generic AEDs, even when bioequivalent standards are satisfied. Generic AEDs have been associated with breakthrough seizures and adverse events that may outweigh cost savings encouraged by third-party payors. Further research is needed comparing brand to generic drugs in a rigorous manner in order to make a consensus statement regarding the safety and equivalency of generic AEDs for all patient populations.

IMPLICATIONS FOR PRACTICE

Generic AEDs may be safely prescribed in certain situations if clinicians are aware of ethical, legal, and practice issues surrounding their use. Sufficient time should be spent educating patients, caregivers, and pharmacists about implications of a switch made without the knowledge of the patient and/or prescriber.

Generic products of antiepileptic drugs: a perspective on bioequivalence and interchangeability

Most antiepileptic drugs (AEDs) are currently available as generic products, yet neurologists and patients are reluctant to switch to generics. Generic AEDs are regarded as bioequivalent to brand AEDs after meeting the average bioequivalence criteria; consequently, they are considered to be interchangeable with their respective brands without loss of efficacy and safety. According to the U.S. Food and Drug Administration (FDA) the present bioequivalence requirements are already so rigorous and constrained that there is little possibility that generics that meet regulatory bioequivalence criteria could lead to therapeutic problems. So is there a scientific rationale for the concerns about switching patients with epilepsy to bioequivalent generics? Herein we discuss the assessment of bioequivalence and propose a scaled-average bioequivalence approach where scaling of bioequivalence is carried out based on brand lot-to-lot variance as an alternative to the conventional bioequivalence test as a means to determine whether switching patients to generic formulations, or vice versa, is a safe and effective therapeutic option. Meeting the proposed scaled-average bioequivalence requirements will ensure that when an individual patient is switched, he or she has fluctuations in plasma levels similar to those from lot-to-lot of the brand reference levels and thus should make these generic products safely switchable without change in efficacy and safety outcomes.

Economic impact of switching from valsartan to other angiotensin receptor blockers in patients with hypertension

BACKGROUND

The approaching availability of lower-cost generic angiotensin receptor blockers (ARBs) may affect formulary policies for patients maintained on the ARB valsartan.

OBJECTIVE

Estimate the economic impact of switching from valsartan (including valsartan-based single-pill combinations) to other ARBs without apparent medical reasons.

RESEARCH DESIGN AND METHODS

Patients with essential hypertension and at least 6 months of continuous valsartan treatment free of hospitalization, cardiovascular events, renal events or ARB-associated adverse events were identified from the MarketScan administrative claims database from January 1, 2004 to March 31, 2008. Those who subsequently switched to a different ARB with at least a 5% copayment decrease (switchers) were matched to those who did not switch (maintainers) according to propensity score quintiles and selected baseline characteristics. Refills were not required after the index fill for the switched-to ARB or maintained valsartan. Matched switchers and maintainers were compared in terms of medication discontinuation, healthcare resource use and costs during the 6 months following the index fill.

RESULTS

A total of 99,926 valsartan maintainers and 2150 switchers (with a mean copayment decrease of $16.5 per month) were identified and matched. After matching, switching from versus maintaining valsartan was associated with an 8% higher risk of medication discontinuation (p < 0.008), 19.1 additional outpatient visits/100 patients (p = 0.002) and 9.3 additional hypertension-related inpatient days/100 patients (p = 0.030). Concurrently, switching from versus maintaining valsartan was associated with higher total medical costs by $748/patient (p < 0.001), driven largely by higher costs for hypertension-related medical services by $492/patient (p = 0.004).

LIMITATIONS

Exact reasons for switching were not available and the study assessed only the short-term impacts of switching.

CONCLUSIONS

Hypertension patients maintained on valsartan who switched to a different ARB with a lower copayment experienced substantial increases in medication discontinuation, healthcare resource use and costs compared to those who maintained valsartan treatment.

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

BACKGROUND

Concerns have been raised over the use of different manufacturers' versions of A-rated antiepileptic drug (AED) formulations in epilepsy patients.

OBJECTIVE

To estimate the association between acute epilepsy exacerbations and switching between different A-rated AEDs.

METHODS

A nested case-control study was conducted using pharmacy and medical claims data from January 1, 2005 through December 31, 2007. 18-65-year-olds who had an epilepsy diagnosis and received AED therapy during 2005 were eligible for study. Cases were defined as individuals with a documented exacerbation of epilepsy in the form of a 2006 or 2007 inpatient or emergency room claim for epilepsy. Controls were from the same population and matched on baseline epilepsy diagnosis and follow-up time since January 1, 2006. The exposure was a switch between A-rated AEDs in the 90 days prior to the matching date. Conditional logistic regression was used to estimate the odds of an epilepsy exacerbation after a switch controlling for important covariates.

RESULTS

A total of 34 216 individuals were eligible for study, of whom 2949 cases were matched to 8847 controls. The unadjusted odds ratio (OR) between a switch and an epilepsy exacerbation was 1.51 (95% CI: 1.29-1.76). After adjusting for potential confounders, the odds ratio was 1.08 (95% CI: 0.91-1.29). Treatment with three or more AEDs or a change in outpatient diagnosis from baseline resulted in ORs of 2.96 (95% CI: 2.48-3.49) and 2.53 (95% CI: 2.28-2.82), respectively.

CONCLUSIONS

After addressing potential confounders, no evidence that A-rated switching was associated with increased acute exacerbations of epilepsy was found. Study limitations include potentially incomplete identification of seizures, no information on indication for medication use, and limited information on duration and severity of disease. This study provides additional insight into the relationship between A-rated AED switching and acute exacerbations of epilepsy.

Understanding therapeutic equivalence in epilepsy

The issues surrounding generic drug substitution in patients with epilepsy are complex. The substitution of one formulation of an antiepileptic drug (AED) for another is controversial. Well-reasoned and defensible cases can be made both for and against such substitution. Although regulatory agencies require that generic and proprietary drugs have similar pharmacokinetic bioequivalence data, their therapeutic efficacy may not necessarily be identical. The paroxysmal nature of epilepsy, the narrow therapeutic index of some AEDs, the need to individualize therapy to achieve seizure control, and the negative consequences of uncontrolled epilepsy distinguishes epilepsy from other clinical conditions. Epilepsy management with AEDs requires careful dose titration and consistent drug exposure at the optimal level for each patient, which can be altered if a different formulation of the AED is substituted. Unexpected variability in plasma concentrations could occur when a patient who has been receiving one formulation of an AED (generic or brand) receives an alternate formulation. Thus, no substitutions should be made for people with epilepsy without the knowledge and approval of the prescribing physician. Patients should be consulted about the substitution, with all risks and benefits carefully explained.

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.

Association between antiepileptic drug switching and epilepsy-related events

Switching between bioequivalent antiepileptic drugs (AEDs) in patients with epilepsy remains a concern because of possible untoward effects owing to a narrow therapeutic range. We investigated the association between switching A-rated AEDs and epilepsy-related events. We conducted a case-control study using claims from the MarketScan database. Cases were defined by an emergently treated epilepsy-related event with the primary diagnosis of epilepsy. Controls had an epilepsy outpatient office visit. Eighty-four of 757 (11.1%) cases and 147 of 2271 (6.5%) controls experienced an A-rated switch. The odds of an epilepsy-related event were 1.78-fold higher for switchers (95% CI 1.35 to 2.36) and, when adjusted for gender and total number of AED prescriptions filled, 1.57-fold higher (95% CI=1.17-2.10). Switching between A-rated formulations of AEDs is associated with an increased risk of emergently treated epilepsy-related events. These findings suggest that care should be taken when considering a switch between A-rated AEDs in patients with epilepsy.

Bioequivalence of antiepileptic drugs: how close is close enough?

During the past few years, the use and substitution of generic antiepileptic drug products has been increasing both in the United States as well as globally. Although these less expensive products may represent an important alternative for many patients, there may be reasons for concern. Despite well-controlled regulatory studies, concerns persist regarding potential therapeutic inequivalence in some patients with epilepsy. These concerns have prompted some in the US neurology community as well as patient advocacy groups to question the current regulatory requirements for both establishing bioequivalence as well as product substitution. In addition, recent data have questioned the actual cost savings associated with generic substitution in this unique patient population. This article reviews current regulatory requirements and pharmacokinetic, biopharmaceutical, and clinical outcome issues that clinicians, pharmacists, and policymakers should consider regarding generic substitution of these complicated agents.

Substitution of anticonvulsant drugs

Changing from branded drugs to generic alternatives, or between different generic formulations, is common practice aiming at reducing health care costs. It has been suggested that antiepileptic drugs (AEDs) should be exempt from substitution because of the potential negative consequences of adverse events and breakthrough seizures. Controlled data are lacking on the risk of substitution. However, retrospective data from large medical claims databases suggest that switching might be associated with increased use of AED and non-AED medications, and health care resources (including hospitalization). In addition, some anecdotal evidence from patients and health care providers' surveys suggest a potentially negative impact of substitution. Well-controlled data are needed to assess the real risk associated with substitution, allowing health care professionals involved in the care of patients with epilepsy to make informed decisions. This paper reviews currently available literature, based on which the authors suggest that the decision to substitute should be made on an individual basis by the physician and an informed patient. Unendorsed or undisclosed substitution at the pharmacy level should be discouraged.