Loss of seizure control associated with generic substitution of carbamazepine

Therapeutic Basis of Generic Substitution of Antiseizure Medications

More than thirty antiseizure medications (ASMs) are available for treating epilepsy. ASMs differ in their potency and efficacy in controlling seizures by acting on diverse targets in the brain, often with variable pharmacokinetics. Moreover, nearly 30% of people with epilepsy have drug-resistant or intractable seizures. Generic substitution of ASMs is a complex issue. It is thought that frequent generic substitution in people with epilepsy may cause problems because the U.S. Food and Drug Administration (FDA) rules allow too much variability across products. The standard bioequivalence range (80% to 125%) appears too broad for many ASMs, especially those exhibiting little separation between therapeutic and toxic levels. Hence, sub-therapeutic concentration may lead to therapeutic failure with seizure recurrence, which could be life threatening. A supra-therapeutic level could result in adverse effects or compliance issues. There are reported issues with generic substitutions of phenytoin, topiramate, levetiracetam, carbamazepine, and lamotrigine. There is discussion in the epilepsy community about additional guidelines, including designation of generic ASMs as Narrow Therapeutic Index (NTI) drugs and how patient education plays a role in generic substitution. Overall, based on the published evidence on specific generic ASMs, FDA bioequivalence standards are not the cause of problems with generic ASM substitution. Rather, it is imperative that physicians and pharmacists provide adequate patient education on what to expect when switching to generic ASMs, including changes in medication shape and color. Another suggestion would be to consider that all ASMs be considered for inclusion in NTI class to prevent the clinical outcome issues associated with generic ASM switching. SIGNIFICANCE STATEMENT: There are critical aspects to consider when switching from a brand name antiseizure medication (ASM) when a generic becomes available or switching between generics. Generic ASMs are interchanged with little consideration of differences in therapeutic equivalence and other clinical factors. This article describes key issues on generic substitution of ASMs and highlights critical pharmacotherapeutic issues associated with generic ASMs.

General Trends in Prices and Prescription Patterns of Anticonvulsants in Germany between 2000 and 2017: Analysis of National and Cohort-Based Data

OBJECTIVE

Our aim was to explore trends in price evolution and prescription volumes of anticonvulsants (AEDs, antiepileptic drugs) in Germany between 2000 and 2017.

METHOD

This study used data from annual reports on mean prescription frequency and prices of defined daily doses (DDD) of AEDs in Germany to analyze nationwide trends. Interrupted time series (ITS) analysis was employed to test for significant effects of several statutory healthcare reforms in Germany on AED price evolution. These data were compared to cohort-based prescription patterns of four German cohort studies from 2003, 2008, 2013, and 2016 that included a total of 1368 patients with focal and generalized epilepsies.

RESULTS

Analysis of national prescription data between 2000 and 2017 showed that mean prices per DDD of third-generation AEDs decreased by 65% and mean prices of second-generation AEDs decreased by 36%, whereas mean prices of first-generation AEDs increased by 133%. Simultaneously, mean prescription frequency of third- generation AEDs increased by 2494%, while there was a substantial decrease in the use of first- (- 55%) and second- (- 16%) generation AEDs. ITS analysis revealed that in particular the introduction of mandatory rebates on drugs in 2003 affected prices of frequently used newer AEDs. These findings are consistent with data from cohort studies of epilepsy patients showing a general decrease of prices for frequently used AEDs in monotherapy by 62% and in combination therapies by 68%. The analysis suggests that overall expenses for AEDs remained stable despite an increase in the prescription of "newer" and "non-enzyme-inducing" AEDs for epilepsy patients.

CONCLUSION

Between 2000 and 2017, a distinct decline in AED prices can be observed that seems predominately caused by a governmentally obtained price decline of third- and second-generation drugs. These observations seem to be the result of a German statutory cost containment policy applied across all health-care sectors. The increasing use of third-generation AEDs to the disadvantage of "old" and "enzyme-inducing" AEDs reflects the preferences of physicians and patients with epilepsy and follows national treatment guidelines.

Switching medication products during the treatment of psychiatric illness

BACKGROUND

The common practice of switching between branded (reference) medications and their corresponding generic products, between generic products, or even from a generic product to a branded medication during the treatment of central nervous system (CNS) disorders may compromise efficacy and/or tolerability.

METHODS

We assessed the published literature from March 1, 2010 through June 30, 2017 via PubMed using the MeSH term 'generics, drugs' alone and in combination with class-specific terms (e.g., 'anticonvulsants', 'mood stabilisers'), for studies detailing outcomes following product switches.

RESULTS

Although some studies comparing the initiation of reference versus generic drugs suggest equivalence between products, several studies detailing a switch between reference and generic products describe reductions in efficacy, reduced medication adherence and persistence, and increased overall health care resource utilization and costs associated with generic substitution.

CONCLUSION

When product switches are considered, they should only proceed with the full knowledge of both patient and provider.

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.

Drug dispensing practices at pharmacies in Bengaluru: A cross-sectional study

OBJECTIVES

Pharmacists are one of the crucial focal points for health care in the community. They have tremendous outreach to the public as pharmacies are often the first-port-of-call. With the increase of ready-to-use drugs, the main health-related activity of a pharmacist today is to assure the quality of dispensing, a key element to promote rational medicine use.

MATERIALS AND METHODS

A cross-sectional study of 200 pharmacies, 100 each in various residential (R) and commercial (C) areas of Bengaluru, was conducted using a prevalidated questionnaire administered to the chief pharmacist or the person-in-charge by the investigators.

RESULTS

Dispensing without prescription at pharmacies was 45% of the total dispensing encounters and significantly higher (χ² = 15.2, P < 0.001, df = 1) in pharmacies of residential areas (46.64%) as compared to commercial areas (43.64%). Analgesics were the most commonly dispensed drugs (90%) without prescription. Only 31% insisted on dispensing full course of antibiotics prescribed and 19% checked for completeness of prescription before dispensing. Although 97% of the pharmacies had a refrigerator, 31% of these did not have power back-up. Only about 50% of the pharmacists were aware of Schedule H.

CONCLUSION

This study shows a high proportion of dispensing encounters without prescription, a higher rate of older prescription refills, many irregularities in medication counseling and unsatisfactory storage practices. It also revealed that about half of the pharmacists were unaware of Schedule H and majority of them about current regulations. Hence, regulatory enforcement and educational campaigns are a prerequisite to improve dispenser's knowledge and dispensing practices.

Potential problems and recommendations regarding substitution of generic antiepileptic drugs: a systematic review of literature

Despite the availability of generic antiepileptic drugs (AEDs), still patients and neurologists hesitate to make a switch due to assorted reasons. The objectives of this review were to evaluate the risks associated with the generic substitution of AEDs. In this context, we also summarized the recommendations of various international societies to treat epileptic patients. We used a number of electronic databases to identify the relevant published studies which demonstrated the potential problems and recommendations regarding generic substitution of AEDs. Of 204 articles found initially, 153 were selected for additional review. Subsequently, 68 articles were finally selected. This review concluded that potential problems linked with the generic substitution of AEDs could be bioequivalence issues, failure of drug therapy, emergence of adverse events and increase in the frequency of seizures. The reasons could be the pharmacokinetics properties of AEDs and unique characteristics of some epilepsy patients. Consequently, the generic substitution of AEDs affects the successful treatment and quality of life of the patients. Various guidelines recommend the well-controlled epileptic patients to avoid switching from brand-to-generic products, generic-to-brand products or generic to some other generic products.

Safety of long-term bisphosphonate therapy for the management of osteoporosis

Drugs in the bisphosphonate class are the most commonly prescribed therapeutic agents for the treatment of osteoporosis. Prospective, randomized, placebo-controlled clinical trials have demonstrated efficacy in reducing fracture risk, with favourable safety profiles, in women with postmenopausal osteoporosis. However, long-term use in clinical practice has been associated with reports of undesirable events not previously recognized. These have included gastrointestinal intolerance, osteonecrosis of the jaw, atypical femur fractures, oesophageal cancer, atrial fibrillation and chronic musculoskeletal pain. Physicians must be alert to newly recognized safety concerns, understand the level of evidence supporting them and be able to effectively communicate the balance of expected benefit and potential risk to patients. Usually, post-marketing adverse events are first presented as case reports or observational studies with variable levels of supporting evidence for plausibility, pathophysiology and causality. Widespread coverage in the news media, which can be alarming to patients and their physicians, may not present a balanced view of the proven benefits, the uncertain risks of therapy and the relative magnitude of these events. There may be confusion about the risks associated with bisphosphonate use for the treatment of osteoporosis versus treatment of other conditions, such as cancer, which typically involves a very different patient population and different doses or frequency of drug administration. Often reports of possible adverse events do not provide information on the number of patients exposed to the drug in proportion to the reported adverse event, or do not describe the incidence of the adverse event in a comparator population not exposed to the drug. Gastrointestinal intolerance with oral bisphosphonates, and hypocalcaemia, acute phase reactions and renal toxicity with intravenous bisphosphonates are characterized by biological plausibility and demonstration of causality. Safety concerns with uncertain biological plausibility and unproven causality include osteonecrosis of the jaw, atypical femur fractures, oesophageal cancer and ocular inflammation. Suspected concerns that are unlikely to be causally related include atrial fibrillation and hepatotoxicity. When making the decision to use a bisphosphonate for the treatment of osteoporosis, the balance between benefit and potential risks according to clinical circumstances of each patient should be considered.

Switching from brand-name to generic psychotropic medications: a literature review

Generic medications do not undergo the rigorous approval process required of original medications. Their effectiveness and safety is expected to be equal to that of their more expensive counterparts. However, several case reports and studies describe clinical deterioration and decreased tolerability with generic substitution. Pubmed was searched from January 1, 1974 to March 1, 2010. The MeSH term "generic, drugs" was combined with "anticonvulsants," "mood stabilizers," "lithium," "antidepressants," "antipsychotics," "anxiolytics," and "benzodiazepines." Additional articles were obtained by searching the bibliographies of relevant references. Articles in English, French, or Spanish were considered if they discussed clinical equivalence of generic and brand-name medications, generic substitution, or issues about effectiveness, tolerability, compliance, or economics encountered with generics. Clinical deterioration, adverse effects, and changes in pharmacokinetics are described with generic substitution of several anticonvulsants/mood stabilizers (carbamazepine, valproate, lamotrigine, gabapentin, topiramate, lithium), antidepressants (amitriptyline, nortriptyline, desipramine, fluoxetine, paroxetine, citalopram, sertraline, venlafaxine, mirtazapine, bupropion), antipsychotics (risperidone, clozapine), and anxiolytics (clonazepam, alprazolam). Generics do not always lead to the anticipated monetary savings and also raise compliance issues. Although the review is limited by publication bias and heterogeneity of the studies in the literature, we believe there is enough concern to advise generic switching on an individual basis with close monitoring throughout the transition. Health professionals should be aware of the stakes around generic substitution especially when health economics promote universal use of generics.

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.

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.

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.

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.

The use of generic medication in epilepsy: a review of potential issues and challenges

Changing from brand name to generic antiepileptic drugs (AEDs) is increasingly being advocated by the authorities, principally for budgetary reasons. However, caution should be exercised since AEDs may have a narrow therapeutic margin, the regimen with AEDs may be complex, the consequences of uncontrolled seizures may be severe, and risk of side effects is relatively high, particularly when seizures are difficult to control. This article focuses on the possible problems that can arise from the substitution of AEDs formulations, such as loss of seizure control and emergence of new side effects. We would advise that patients stay on the same formulation of the first AED, whether a brand name or generic AED. Switching AED formulations should always be done with the necessary caution and under the physician's supervision. Closer follow-up during the transitional period is necessary, and dosage adjustment may be required. The patient should be given full and correct advice about risks involved in switching AED formulations.

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

PURPOSE

Although antiepileptic drugs (AEDs) with multisource generic alternatives are becoming more prevalent, no case-control studies have been published examining multisource medication use and epilepsy-related outcomes. This study evaluated the association between inpatient/emergency epilepsy care and the occurrence of a recent switch in AED formulation.

METHODS

A case-control analysis was conducted utilizing the Ingenix LabRx Database. Eligible patients were 12-64 years of age, received >or=145 days of AEDs in the preindex period, had continuous eligibility for 6 months preindex, and no prior inpatient/emergency care. Cases received care between 7/1/2006 and 12/31/2006 in an ambulance, emergency room, or inpatient hospital with a primary epilepsy diagnosis. Controls had a primary epilepsy diagnosis in a physician's office during the same period. The index date was the earliest occurrence of care in each respective setting. Cases and controls were matched 1:3 by epilepsy diagnosis and age. Odds of a switch between "A-rated" AEDs within 6 months prior to index were calculated.

RESULTS

Cases (n = 416) had 81% greater odds of having had an A-rated AED formulation switch [odds ratio (OR) = 1.81; 95% confidence interval (CI) = 1.25 to 2.63] relative to controls (n = 1248). There were no significant differences between groups regarding demographics or diagnosis. Significant differences were found with regard to medical coverage type (case Medicaid = 4.6%, control Medicaid = 1.8%, p = 0.002). Post hoc analysis results excluding Medicaid recipients remained significant and concordant with the original analysis.

DISCUSSION

This analysis found an association between patients receiving epilepsy care in an emergency or inpatient setting and the recent occurrence of AED formulation switching involving A-rated generics.

Identification of adverse reactions that can occur on substitution of generic for branded lamotrigine in patients with epilepsy

OBJECTIVE

The aim of this study was to characterize outcomes in patients with epilepsy who experienced adverse reactions on switching from branded to generic lamotrigine and who were subsequently switched back to the branded formulation.

METHODS

This case-series analysis used data from patients identified through a survey of Ontario pharmacists, where Health Canada adverse-reaction forms submitted to pharmacists by physicians were retrieved, and from a physician chart audit and survey. Data from male and female patients with epilepsy who experienced an adverse reaction on switching from branded to generic lamotrigine and thus were switched back to the branded formulation were included.

RESULTS

The pharmacists' survey indicated that 11 of 14 retrieved adverse-reaction forms described patients with epilepsy who experienced loss of seizure control when generic lamotrigine was substituted for branded drug. Seizure control was regained in 8/10 (80%) patients with reported outcomes when they were switched back to the branded drug. Based on data from the physician survey response rate, 130/544 [24%1], 5/95 (5%) reported filing a Health Canada adverse-reaction form requesting that a patient be dispensed branded lamotrigine rather than the generic formulation. Six physicians provided data on 9 patients who experienced adverse reactions on a brand-to-generic switch, 8 of which were due to loss of seizure control. Seizure control was regained in all but 1 case on a switch back to the branded drug.

CONCLUSIONS

The results of this small case-series investigation suggest that some patients may experience loss of seizure control when generic lamotrigine is substituted for the branded formulation. The degree of risk was not assessable based on available data, which are merely suggestive because of the observational nature of the study.

Utilisation des médicaments génériques des anti-épileptiques en France : résultats d’une enquête auprès des neurologues et revue de la littérature

INTRODUCTION

The use of generic substitution for antiepileptic drugs is more and more frequent but remains controversial.

PURPOSE AND METHODS

This survey aimed to assess physicians' feelings towards effectiveness, tolerability and clinical impact of generic substitution of antiepileptic drugs on their patients. A questionnaire was sent to all French private neurologists and hospital specialists in epilepsy. Their responses were recorded from December 2005 to March 2006.

RESULTS

A total of 312 neurologists responded. A few prescribed generic antiepileptic drugs; but a few as well indicated not to switch their prescription. Most of them felt discomfort by generic substitution. One third reported breakthrough seizures or new adverse events after generic substitution and 70p.cent extra phone consultation.

DISCUSSION

Neurologists' reluctance with prescribing generic AEDs may be explained by several different facts: no controlled study about the safety and efficacy of generic AEDs as compared with brand name drugs, substitutions by pharmacists without their agreement, lack of medical information about generic AEDs, symbolic dimension of the treatment, and, most of all, the fear of breakthrough seizures in patients good controlled.

CONCLUSION

A prospective controlled evaluation of the safety and efficacy of generic substitution in epilepsy needs to be performed.

Compulsory Generic Switching of Antiepileptic Drugs: High Switchback Rates to Branded Compounds Compared with Other Drug Classes

PURPOSE

Compulsory generic substitution of antiepileptic drugs (AEDs) may lead to adverse effects in epilepsy patients because of seizure recurrence or increased toxicity. The study objectives were (a) to quantify and compare the switchback rates from generic to brand-name AEDs versus non-AEDs, and (b) to assess clinical implications of switching from branded Lamictal to generic lamotrigine (LTG) and whether signals exist suggesting outcome worsening.

METHODS

By using a public-payer pharmacy-claims database from Ontario, Canada, switchback rates from generic to branded AEDs [Lamictal, Frisium (clobazam; CLB), and Depakene (VPA; divalproex)] were calculated and compared with non-AED long-term therapies, antihyperlipidemics and antidepressants, in January 2002 through March 2006. We then assessed pharmacy utilization and AED dosage among LTG patients switching back to branded Lamictal compared with those staying on generic formulation.

RESULTS

The 1,354 patients (403 monotherapy, 951 polytherapy) were prescribed generic LTG, of whom 12.9% switched back to Lamictal (11.7% monotherapy, 13.4% polytherapy). Switchback rates of other AEDs were approximately 20% for CLB and VPA. The switchback rates for AEDs were substantially higher than for non-AEDs (1.5-2.9%). Significant increases in LTG doses were observed after generic substitution for those who did not switch back (6.2%; p<0.0001). The average number of codispensed AEDs and non-AED drugs significantly increased (p<0.0001) after LTG generic entry, especially in the generic group.

CONCLUSIONS

These results reflect poor acceptance of switching AEDs to generic compounds. They may also indicate increased toxicity and/or loss of seizure control associated with generic AED use.

Recommendations of the Italian League Against Epilepsy Working Group on Generic Products of Antiepileptic Drugs

The availability of generic products of antiepileptic drugs (AEDs) has been increasing in recent years. In view of the importance of the issue, the Italian League against Epilepsy (LICE) set up an ad hoc working group whose task was to assess available evidence on the efficacy and safety of generic AEDs in the treatment of epilepsy and to produce recommendations on their use. A careful review of the literature revealed no adequately powered randomized controlled trials that assessed the risk/benefit ratio of generic substitution. Although there have been reports of loss or worsened seizure control, or appearance of adverse events, following the switch from brand products to generics, a critical assessment of the evidence generally does not allow us to establish a cause-effect relationship between the switch and a change in clinical status. Overall, the working group concluded that generic AEDs meeting current regulatory criteria for bioequivalence represent a valuable choice in the management of epilepsy by allowing a substantial reduction of treatment costs, particularly in patients initiating monotherapy or adjunctive treatment and in those with persistent seizures. The working group considered that in patients who achieved seizure freedom a modest change in plasma drug levels, which may occasionally occur even after substitution of products that meet bioequivalence criteria, could in rare cases lead to seizure breakthrough. Therefore, generic substitution is not recommended in patients who achieved seizure remission. Switches between a particular generic and another generic should also be preferably avoided. Finally, sustained-release AED formulations should not be used interchangeably with immediate-release brand or generic products. Patients need to be informed about the stringent criteria that currently govern the approval of generic products and about the implications of the use of generic AEDs, and their opinion should be taken into consideration at the time of prescribing.

Patients’ attitudes towards and experiences of generic drug substitution in Norway

OBJECTIVE

The aim of the study was to assess patients' attitudes towards and experiences of generic substitution 3 years after generic substitution of prescription medicines was permitted in Norway.

METHODS

Prescriptions from 2,128 consecutive patients in a Norwegian pharmacy were retrospectively reviewed to identify all patients (n=274) receiving eight or more different prescription drugs on the fifth level in the Anatomical Therapeutic Chemical (ATC) classification system during the last 6 months. An age-adjusted control group (n=269) of patients receiving three to seven different prescription drugs was randomly selected. Of the 543 patients, 386 were eligible for inclusion. Both groups received a mailed questionnaire addressing their experiences with and attitudes towards generic substitution.

RESULTS

The overall response rate was 73% (281/386) and the average age of the respondents was 66 years old. The study found that patients who reported to have received information from their physician or the pharmacy about generic substitution were more likely to have switched (P<0.001). About half (138/281) of the patients had experienced a generic switch, and a higher proportion of the polypharmacy patients had their medication substituted compared to the control patients (P<0.001). Altogether 50 (36%) of the patients who had experienced a switch, reported one or more negative experiences connected to the substitution, and 29 of these (21%) reported an overall negative experience after the change. The experiences of the patients were not related to age, gender, or number of medications or information about generics from either the pharmacy or the physician. About 41% of the patients would not switch if they had no personal economic incentives.

CONCLUSIONS

About 1/3 of the patients who had their medication substituted reported negative experiences. Generic drug substitution for a number of patients is not considered an equal alternative to branded drugs, and these patients may need additional information and support. The lack of correlation between patient experiences and age, gender, and medical regimen complexity is interesting and should be investigated further.

Are there potential problems with generic substitution of antiepileptic drugs?

In response to increasing cost pressures, healthcare systems are encouraging the use of generic medicines. This review explores potential problems with generic substitution of antiepileptic drugs (AEDs). A broad search strategy identified approximately 70 relevant articles. Potential problems with generic substitution included: The limited evidence (mainly case reports with some pharmacokinetic studies) appears to support these concerns for older AEDs. As a result, restrictions on use of specific generic AEDs are in place in some countries and recommended by some lay epilepsy organisations. As more AEDs lose patent protection, it is important to examine the question of whether generic substitution may pose problems for patients with epilepsy, and whether there should be safeguards to ensure that both physician and patient are informed when generic substitution occurs.

Patient and physician reactions to generic antiepileptic substitution in the treatment of epilepsy

BACKGROUND

The clinical and economic consequences of generic antiepileptic drug (AED) substitution are not yet fully understood. This article provides a broad perspective of generic AED substitution in five countries.

METHODS

Two cross-sectional telephone-based surveys (patient and physician) were undertaken in Canada, the United Kingdom, France, Germany, and Spain. A total of 1409 interviews, 974 patients and 435 physicians, were completed.

RESULTS

Across all countries studied, patients and physicians alike have elevated concerns about the safety and efficacy of generic AEDs as compared with drugs for acute care.

CONCLUSION

There is an opposition to generic substitution by both patients and physicians, especially with concern over increased breakthrough seizure risk. Further evidence is required to understand how costs and effects of generic AED substitution affect patient welfare.

Patterns of care, outcomes, and direct health plan costs of antiepileptic therapy: a pharmacoeconomic analysis of the available carbamazepine formulations

BACKGROUND

Although generic formulations of immediate-release carbamazepine (IR-CBZ) are available, extended-release delivery systems may offer important advantages, including the convenience of less-frequent administration and smaller peak-to-trough serum carbamazepine (CBZ) fluctuations.

OBJECTIVE

The aim of this study was to compare the patterns of pharmacotherapy, rates of adverse events, and the utilization costs among patients treated with the available CBZ formulations (ie, generic and branded IR-CBZ, and extended-release CBZ (ER-CBZ) capsules [Carbatrol, Shire US Inc., Wayne, Pennsylvania] and tablets [Tegretol-XR, Novartis Pharmaccuticals Corporation, East Hanover, New Jersey]).

METHODS

Data were retrieved from the PharMetrics patient-centric database (which contains integrated claims data for almost 36 million unique patients from 61 US health plans) for patients who were diagnosed with epilepsy and initiated CBZ between July 1999 and June 2001. Patient demographic and clinical characteristics, adverse events, discontinuations, CBZ therapy switches, and utilization and costs for related care subsequent to treatment initiation were recorded. Annual rates of adverse events and discontinuations were calculated, and the risks of these events were compared across treatment groups.

RESULTS

Data were gathered for 1737 patients. The branded CBZ group was demographically and clinically different than the other groups (ie, migraine and cerebral palsy prevalence) and therefore was excluded from event-risk analyses. Results of the proportional hazards regression analysis indicated that Tegretol-XR patients were more likely to experience common central nervous system (CNS)-related adverse events relative to Carbatrol (hazard ratio, 1.67; P = 0.043). A lower percentage of subjects switched off ER-CBZ relative to IR-CBZ (Carbatrol, 5.2%; Tegretol-XR, 5.7%; generic IR-CBZ, 13.0%; branded IR-CBZ, 16.7%). Differences in mean payments for epilepsy-related health care services at 1 year among Carbatrol, Tegretol-XR, and branded or generic CBZ did not reach statistical significance.

CONCLUSIONS

Among the available CBZ formulations, Carbatrol was associated with a lower incidence of common CNS adverse events. ER-CBZ formulations were also associated with reduced likelihood of therapy discontinuation or switching CBZ medications, relative to patients taking generic IR-CBZ, in this retrospective data analysis.

Prescribing antiepileptic drugs: should patients be switched on the basis of cost?

To assess the costs of switching from one antiepileptic drug (AED) to another, all associated direct and indirect costs, not only drug acquisition costs, must be considered. The perspective of the healthcare system evaluated in cost-effectiveness analysis is of crucial importance. Multiple clinical factors can influence clinical decisions regarding switching AEDs. The economic cost of poorly controlled epilepsy is enormous and the most cost-effective intervention is an AED that provides total seizure control. Cost-minimisation studies have evaluated costs associated with various medications. If only efficacy and adverse events were considered, then the 'older' AEDs were generally more cost effective than the 'newer' AEDs. Most studies only examine very specific clinical situations and are not suitable for establishing general clinical recommendations. The pharmacoeconomics of AED choice is highly country specific. While switching to generic formulations is, in general, cost effective, some changes may be detrimental and more costly than remaining on the trade name preparation. For example, as a result of differences in bioavailability and possible loss of seizure control, changing patients to generic phenytoin and carbamazepine can be problematic. Fosphenytoin may only be cost effective in certain clinical situations compared with intravenous phenytoin. Seizure control should not be sacrificed on the basis of costs alone, as the major endpoint in treating epilepsy with AEDs is seizure control without adverse effects. Switching AEDs in clinical practice still depends on the individual clinical situation and choosing AED therapy solely on the basis of initial acquisition costs is unlikely to be cost effective in the long-term care of patients with epilepsy.

The bioequivalence and therapeutic efficacy of generic versus brand-name psychoactive drugs

BACKGROUND

For the purposes of drug approval, the interchangeability of a generic drug and the corresponding brand-name drug is based on the criterion of "essential similarity," which requires that the generic drug have the same amount and type of active principle, the same route of administration, and the same therapeutic effectiveness as the original drug, as demonstrated by a bioequivalence study. However, bioequivalence and therapeutic effectiveness are not necessarily the same.

OBJECTIVE

This review summarizes available data comparing the bioequivalence and therapeutic efficacy of brand-name psychoactive drugs with those of the corresponding generic products.

METHODS

Relevant information was identified through searches of MEDLINE, Current Contents/Clinical Medicine, and EMBASE for English-language articles and English abstracts of articles in other languages published between 1975 and the present. The search terms used were generic drug, branded drug, safety, toxicity, adverse events, clinical efficacy, bioequivalence, bioavailability, psychoactive drugs, and excipients.

RESULTS

Few publications compared the bioequivalence and efficacy of brand-name and generic psychoactive drugs. Those that were identified revealed differences in the efficacy and tolerability of brand-name and generic psychoactive drugs that had not been noted in the original bioequivalence studies. Specifically, l study found that plasma levels of phenytoin were 31% lower after a switch from a brand-name to a generic product. Several controlled studies of carbamazepine showed a recurrence of convulsions after the shift to a generic formulation. After a sudden recurrence of seizures when generic valproic acid was substituted for the brand-name product, an investigation by the US Food and Drug Administration found a difference in bioavailability between the 2 formulations. Statistically significant differences in pharmacokinetic variables have been reported in favor of brand-name versus generic diazepam (P < 0.001). Finally, a case report involving paroxetine mesylate cast doubt on the tolerability and efficacy of the generic formulation.

CONCLUSION

The essential-similarity requirement should be extended to include more rigorous analyses of tolerability and efficacy in actual patients as well as in healthy subjects.

A practical approach for evaluating population and individual bioequivalence

Pharmacokinetic measurements provided by subjects to each of two formulations of a drug have a joint distribution that can be characterized by parameters reflecting scale and correlation as well as location. The bioavailability of the formulations can be expressed in terms of the means of the marginal distributions, their means and variances, or the marginal means and variances and the joint correlation. These expressions correspond, respectively, to 'average', 'population', and 'individual' bioequivalence when the joint distribution of the measurements is bivariate normal. Current proposals for assessing the degree of bioequivalence of two formulations are based on statistics that are composites of variance components and squares of expected mean differences from a mixed linear model. There are technical and practical issues associated with these proposals, particularly that they require more complicated designs than the familiar 2x2 cross-over. This paper describes an alternative approach that can be applied with standard 2x2 cross-over designs, and that provides evaluations of population and individual bioequivalence that should be adequate for all practical clinical purposes. The approach is based on easily computed correlation and regression coefficients whose statistical properties under normality are well known and for which non-parametric and robust alternatives exist when normality cannot be assumed. The approach yields conclusions consistent with those obtained by the current proposals when applied to data sets supplied by the FDA. In the cases where the conclusions do not match, the new approach appears to be more consistent with the data.

Pharmacokinetic comparison of Sinemet and Atamet (generic carbidopa/levodopa): a single-dose study

We compared the pharmacokinetic and motor responses of Sinemet and Atamet (generic carbidopa/levodopa) in patients with Parkinson's disease. Thirty Parkinson's disease patients (10 previously untreated, 10 with early disease, and 10 with motor fluctuations/dyskinesia) participated in a single-dose double-blind study. Following administration of an equivalent oral dose of Sinemet and Atamet on two separate days, we compared the peak plasma concentration, time to peak plasma concentration, area under the curve, total motor score, tapping score, and walking time. The mean time to peak plasma concentrations was 49 min with Sinemet and 47 min with Atamet, the mean peak plasma concentration was 1,273 ng/ml with Sinemet and 1,153 ng/ml with Atamet, and the mean area under the curve was 2,295 micrograms/ml/h with Sinemet and 2,330 micrograms/ml/h with Atamet. Similarly, there was no significant difference between total motor score, tapping score, or walking time. In this single-dose study, there were no significant differences in pharmacokinetic and motor responses between Sinemet and Atamet.