Refilling and switching of antiepileptic drugs and seizure-related events

Considerations over a Case of Suspected Therapeutic Failure in Pediatric Patients after Switching Valproate Manufacturers

Introduction: Product switching followed by suspected adverse events are common and unsettling for antiepileptic drugs. The objective of this case study was to describe the investigation performed after report of suspected therapeutic failure in pediatric patients following a switch to a different valproate manufacturer and identify strategies concerning medication management for improving therapeutic outcomes. Case description: It was reported that different pediatric patients' condition changed (agitation/ seizures) after refilling the same drug prescription (sodium valproate syrup) from a different manufacturer. Medical staff reported a suspected therapeutic failure and some units of the product batch associated with the problem were seized by the local Post-marketing Surveillance Service for investigation of potential quality deviations. The seized units were evaluated by the State's Surveillance Laboratory, nevertheless, drug potency was found to be 98.7%. Conclusion: We consider that the reported event could be associated with aspects of medication use, i.e. potential dose measurement deviations resulting from remaining of residual liquid in the cup or eventual delay at prescription refilling process and consequential - even though brief - pharmacotherapy discontinuity. Patient education and counseling by pharmacists are essential for preventing drug-related problems and enhancing positive outcomes of pharmacotherapy.

Manufacturer switch of anti-seizure drugs may not increase the risk of seizure recurrence in Children: A nationwide study of prescription data in Germany

OBJECTIVE

Several publications on the exchangeability of antiepileptic drugs in clinical settings revealed an increased risk for seizure recurrence after changing the manufacturer of anti-seizure drugs (ASD) in adults, possibly due to a decline of adherence. It is unclear whether this holds true in children and adolescents.

METHODS

Patient data of children and adolescents (<18 years) were collected anonymously from 236 German pediatricians and pediatric neurologists between January 2011 and December 2018 using the IMS® Disease Analyzer database (IQVIA, Frankfurt, Germany). Patients with epilepsy were included if at least 2 prescriptions within 360 days and 1 within 180 days prior to the index date were available. The cohort was separated into a seizure group and seizure-free controls. Both groups were matched 1:1 according to age, gender, insurance status, and treating pediatrician. The risk for seizure recurrence after a manufacturer switch of the same ASD at the last prescription before the index date was analyzed using a multivariate regression model.

RESULTS

A total of 678 children and adolescents with epilepsy were included (each group: n = 339; age: 9.6 ± 4.4 years). Comparing both groups, the risk for seizures recurrence was not increased after a manufacturer switch had occurred. Albeit changes during the last prescription before the index date had occurred more often in the seizure-free group, neither change of branded and generic products nor substances reached significance. Only change of ASD strength showed a significantly reduced odds ratio for seizures (OR 0.40, 95% CI 0.24-0.65, p < 0.001).

SIGNIFICANCE

In contrast to the available evidence in adults, changing the manufacturer did not appear to increase the risk for seizure recurrence in previously seizure-free children and adolescents with epilepsy.

Assessment of Variation in State Regulation of Generic Drug and Interchangeable Biologic Substitutions

IMPORTANCE

Brand-name drugs, including biologics, have been the primary source of increasing prescription drug spending in the US. Each state has drug product selection laws that regulate whether and how pharmacists can substitute prescriptions for brand-name drugs with more affordable equivalents, either small-molecule generic drugs or interchangeable biologics, but the details of these laws can vary.

OBJECTIVE

To examine the variation in state drug product selection laws with regard to factors that may affect which version of a drug is dispensed.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional analysis was performed, using a legal database, to obtain information on state laws of all states plus Washington, DC, as they existed on September 1, 2019.

EXPOSURES

Whether substitution was mandatory or permissive, patient consent was needed prior to substitution, patient notification of substitution was required independent of the drug's packaging, and/or pharmacists were protected from special risk of liability for substitution.

MAIN OUTCOMES AND MEASURES

For small-molecule and biologic drugs, descriptive statistics were generated for the 4 exposure variables. In addition, for small-molecule drugs, a generic substitution score with a maximum of 1 point was assigned for each exposure variable (range, 0-4 points), with higher scores indicating regulatory requirements limiting substitution.

RESULTS

This cross-sectional analysis of the generic drug substitution regulations in the 50 US states and Washington, DC, found that for small-molecule drugs, 19 states required pharmacists to perform generic substitution; 7 states and Washington, DC, required patient consent; 31 states and Washington, DC, mandated patient notification independent of the drug's packaging, and 24 states did not explicitly protect pharmacists from greater liability. Nine states and Washington, DC, had a generic substitution score for small-molecule drugs of 3 or higher, and 45 states had more stringent requirements for interchangeable biologic substitution, most commonly mandatory physician notification.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that there is a need for optimizing state drug product selection laws to promote generic and interchangeable biologic substitution, which may help improve medication adherence and reduce drug spending.

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.

Evaluation of Switching Patterns in FDA's Sentinel System: A New Tool to Assess Generic Drugs

INTRODUCTION

Nearly 90% of drugs dispensed in the US are generic products.

OBJECTIVE

The aim of this study was to develop and implement a tool for analyzing manufacturer-level drug utilization and switching patterns within the US Food and Drug Administration's Sentinel system.

METHODS

A descriptive tool was designed to analyze data in the Sentinel common data model and was tested with two case studies-metoprolol extended release (ER) and lamotrigine ER-using claims data from four Sentinel data partners. We plotted initiators of each brand and generic product over time. For metoprolol ER, we evaluated rates of switching from generics around the time of manufacturing issues. For lamotrigine ER, we examined rates of switching back to the brand among those who switched from brand to generic.

RESULTS

We identified 1,651,285 initiators of metoprolol ER products between July 2008 and September 2015. We observed a large decrease in monthly metoprolol ER initiators (from 25,465 in December 2008 to 13,128 in February 2009), corresponding to recalls by generic manufacturers. We observed simultaneous increases in utilization of the authorized generic and brand products. We identified 4266 initiators of lamotrigine ER with an epilepsy diagnosis between January 2012 and September 2015. Among those who switched from brand to generic, the cumulative incidence of switching back was close to 20% at 2 years. Switchback rates were higher for the first available generic products.

CONCLUSIONS

This developed tool was able to elucidate novel utilization and switching patterns in two case studies. Such information can be used to support surveillance of generic drugs and biosimilars.

A Survey of Patients' Perceptions of Pill Appearance and Responses to Changes in Appearance for Four Chronic Disease Medications

BACKGROUND

Generic versions of a drug can vary in appearance, which can impact adherence.

OBJECTIVE

To assess the preferences, perceptions, and responses of patients who experienced a change in the appearance of a generic medication.

DESIGN

Cross-sectional survey of patients from a large commercial health plan.

PARTICIPANTS

Adults receiving generic versions of lisinopril, fluoxetine, lamotrigine, or simvastatin who experienced a change in the color or shape of their pills between March 2014 and November 2015.

MAIN MEASURES

Likert-scale responses to questions concerning perceptions of generic drug safety and effectiveness, reliance on and preferences for pill appearance, and responses to pill appearance changes. Multivariable logistic regression-modeled predictors of seeking advice and adjusting use following a pill appearance change.

KEY RESULTS

Of 814 respondents (response rate = 41%), 72% relied on pill appearance to ensure they took the correct medication. A similar percentage wanted their pills to remain the same color (72%), shape (71%), and size (75%) upon refill, but 58% would not have paid a $1 premium on a $5 co-pay to ensure such consistency. Most respondents (86%) wanted their pharmacists to notify them about pill appearance changes, but only 37% recalled such notification; 21% thought they received the wrong medication, and 8% adjusted medication use. Younger respondents (18-33 vs. 50-57 years) were more likely to seek advice (odds ratio [OR] = 1.91; 95% confidence interval [CI],1.02-3.59), and respondents with lower household income (< $30,000 vs. > $100,000) were more likely to adjust medication use (OR = 3.40; 95% CI,1.09-10.67).

CONCLUSIONS

Requiring uniform pill appearance may help increase adherence but presents challenges. Standardized pharmacy notification and education policies may be a more feasible short-term solution.

Non-pharmacological Effects in Switching Medication: The Nocebo Effect in Switching from Originator to Biosimilar Agent

The nocebo effect is defined as the incitement or the worsening of symptoms induced by any negative attitude from non-pharmacological therapeutic intervention, sham, or active therapies. When a patient anticipates a negative effect associated with an intervention, medication or change in medication, they may then experience either an increase in this effect or experience it de novo. Although less is known about the nocebo effect compared with the placebo effect, widespread interest in the nocebo effect observed with statin therapy and a literature review highlighting the nocebo effect across at least ten different disease areas strongly suggests this is a common phenomenon. This effect has also recently been shown to play a role when introducing a medication or changing an established medication, for example, when switching patients from a reference biologic to a biosimilar. Given the important role biosimilars play in providing cost-effective alternatives to reference biologics, increasing physician treatment options and patient access to effective biologic treatment, it is important that we understand this phenomenon and aim to reduce this effect when possible. In this paper, we propose three key strategies to help mitigate the nocebo effect in clinical practice when switching patients from reference biologic to biosimilar: positive framing, increasing patient and healthcare professionals' understanding of biosimilars and utilising a managed switching programme.

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.

Generic Versions of Narrow Therapeutic Index Drugs: A National Survey of Pharmacists' Substitution Beliefs and Practices

Small changes in bioavailability of narrow therapeutic index (NTI) drugs can alter clinical outcomes, raising concern over generic NTI substitution. We surveyed pharmacists to identify their perceptions of generic NTI drugs, their frequency of performing generic NTI substitution, and predictors of this behavior. Of 710 respondents (33% response rate), 87% perceived generic NTI drugs as effective as their brand-name versions and 94% as safe. Whereas 82% almost always performed generic NTI substitution for initial prescriptions, only 60% did for refills. Pharmacists in non-chain settings (odds ratio (OR) = 2.37; 95% confidence interval (CI) = 1.40-4.02), in practice longer (per year OR = 1.04; 95% CI = 1.02-1.06), in states with affirmative patient consent laws (OR = 1.88; 95% CI = 1.06-3.32), and in states with NTI-specific substitution requirements (OR = 1.95; 95% CI = 1.16-3.26) were more likely not to substitute initial prescriptions. Education of non-chain and veteran pharmacists and elimination of affirmative patient consent and NTI-specific substitution requirements could increase generic NTI substitution.

Safety of switching from brand-name to generic levetiracetam in patients with epilepsy

Purpose

The approach to the use of generic antiepileptic drugs has recently evolved from major concern to general acceptance, but the evidence related specifically to the safety of switching from brand-name to generic levetiracetam (LEV) is scarce. The aim of the study was to assess the risk of increased frequency of seizures or other adverse events after replacement of a brand-name LEV with a generic one.

Patients and methods

This retrospective analysis included 159 patients treated with LEV in a tertiary outpatient epilepsy clinic. We included all patients diagnosed with epilepsy who were treated with LEV as at March 1, 2013. Most patients were forced to switch to the generic LEV because of the sudden rise in cost of the branded LEV. We recorded data on age, sex, age at onset of epilepsy, type of epilepsy, and its treatment. We analyzed data from one visit before potential switching and from two visits after the potential switching. The interval between visits was typically 3 months. We registered an increase in the frequency of seizures and in the occurrence of adverse events.

Results

Among 151 subjects who switched to generic LEV after March 1, 2013, increased frequency of seizures was noted in 9 patients (6%) during the first follow-up visit. Patients with increased frequency of seizures did not differ from other patients regarding sex, age, age at the onset of epilepsy, and the median dose of LEV before switching or the median duration of treatment with LEV before switching. Two patients returned to brand-name LEV. Adverse events were noted in six other patients (4%) and included somnolence, irritability, or dizziness.

Conclusion

Switching from brand-name to generic LEV is generally safe.

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.

Potentially disruptive life events: what are the immediate impacts on chronic disease management? A case-crossover analysis

OBJECTIVE

To explore the association between unexpected potentially disruptive life events in a patient or family member that may challenge an individual's ability to take medications as prescribed and the discontinuation of evidence-based medications for common, chronic conditions. Understanding the relationship between medication adherence and life stressors, especially those that can be identified using administrative data, may help identify patients at risk of non-adherence.

DESIGN

Observational self-controlled case-crossover design.

SETTING

Individuals in a nationally representative US commercial health insurance database.

PARTICIPANTS

Adult individuals who initiated an oral hypoglycaemic, antihypertensive and/or statin and subsequently stopped the medication for ≥90 days.

MAIN OUTCOME MEASURE

Potentially disruptive life events among patients and their family members measured in the 30 days just before the medication was discontinued ('hazard period') compared with the 30 days before this period ('control period'). These events included personal injury, hospitalisation, emergency room visits, changes in insurance coverage, acute stress or acute anxiety.

RESULTS

Among the 326 519 patients meeting study criteria who discontinued their chronic disease medications, 88 896 (27.2%) experienced at least one potentially disruptive life event. Newly experiencing an injury (OR: 1.26, 95% CI 1.12 to 1.42), an emergency room visit (OR: 1.19, 95% CI 1.13 to 1.26) and acute stress (OR: 1.19, 95% CI 1.08 to 1.31) were associated with discontinuation. Life events among patients' family members did not appear to be associated with medication discontinuation or occurred less frequently just prior to discontinuation.

CONCLUSIONS

Potentially disruptive life events among individuals identified using routinely collected claims data are associated with discontinuation of chronic disease medications. Awareness of these events may help providers or payers identify patients at risk of non-adherence to maximise patient outcomes.

A comparison of the intrasubject variation in drug exposure between generic and brand-name drugs: a retrospective analysis of replicate design trials

AIMS

The aim of the present study was to investigate whether differences in total and peak drug exposure upon generic substitution are due to differences between formulations or to intrasubject pharmacokinetic variability of the active substance.

METHODS

The study was designed as a retrospective reanalysis of existing studies. Nine replicate design bioequivalence studies representing six drug classes - i.e. for alendronate, atorvastatin, cyclosporin, ebastine, exemestane, mycophenolate mofetil, and ropinirole - were retrieved from the Dutch Medicines Regulatory Authority.

RESULTS

In most studies, the intrasubject variability in total and peak drug exposure was comparable for the brand-name [in the range 0.01-0.24 for area under the concentration-time curve (AUCt ) and 0.02-0.29 for peak plasma concentration (Cmax ) on a log scale] and generic (0.01-0.23 for AUCt and 0.08-0.33 for Cmax ) drugs, and was comparable with the intrasubject variability upon switching between those drugs (0.01-0.23 for AUCt and 0.06-0.33 for Cmax ). The variance related to subject-by-formulation interaction could be considered negligible (-0.069 to 0.047 for AUCt and -0.091 to 0.02 for Cmax ).

CONCLUSION

In the investigated studies, the variation in total and peak exposure seen when a patient is switched from a brand-name to a generic drug is comparable with that seen following repeated administration of the brand-name drug in the patient. Only the intrasubject variability seems to play a crucial and decisive role in the variation in drug exposure seen; no additional formulation-dependent variation in exposure is observed upon switching. Thus, our data support that, for the medicines that were included in the present investigation, from a clinical pharmacological perspective, the benefit-risk balance of a generic drug is comparable with that of the brand-name drug.

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.

The impact on health outcomes and healthcare utilisation of switching to generic medicines consequent to reference pricing: the case of lamotrigine in New Zealand

BACKGROUND

Many countries have implemented generic reference pricing and substitution as methods of containing pharmaceutical expenditure. However, resistance to switching between medicines is apparent, especially in the case of anti-epileptic medicines.

OBJECTIVES

This study sought to exploit a nation-wide policy intervention on generic reference pricing in New Zealand to evaluate the health outcomes of patients switching from originator to generic lamotrigine, an anti-epileptic medicine.

METHODS

A retrospective study using the national health collections and prescription records was conducted comparing patients who switched from originator brand to generic lamotrigine with patients who remained on the originator brand. Primary outcome measures included switch behaviour, changes in utilisation of healthcare services at emergency departments, hospitalisations and use of specialist services, and mortality.

RESULTS

Approximately one-quarter of all patients using the originator brand of lamotrigine switched to generic lamotrigine, half of whom made the switch within 60 days of the policy implementation. Multiple switches (three or more) between generic and brand products were evident for around 10% of switchers. Switch-back rates of 3% were apparent within 30 days post-switch. No difference in heath outcome measures was associated with switching from originator lamotrigine to a generic equivalent and hence no increased costs could be found for switchers.

CONCLUSIONS

Switching from brand to generic lamotrigine is largely devoid of adverse health outcomes; however, creating an incentive to ensure a greater proportion of patients switch to generic lamotrigine is required to achieve maximal financial savings from a policy of generic reference pricing.

From antiretroviral originator to generic drugs: bioequivalence and pharmacovigilance

Antiretroviral drugs have been available in generic form in developing countries, which has expanded access to treatment; they have also become available in developed countries more recently.

OBJECTIVES

The validation of generic drugs (GD) compared to originator drugs (OD) is mandatory to ensure that using generics will lead to a decreased cost of treatment.

RESULTS

The results were obtained by analyzing published data as well as European Medicines Agency recommendations.

METHOD

The GD should have the same qualitative and quantitative active principle formula, the same pharmaceutical forms, and the same criteria in terms of quality, effectiveness, and safety. This equivalence is based on bioequivalence rules: comparison of the concentration/time curves (AUC); Cmax and Tmax (90%), for which the confidence intervals in the range of 80-125% should be included. Naturally, that does not mean that the concentrations can vary from 80 to 125%: this would indicate unacceptable deviations. Conforming to these criteria allows substituting an OD by a GD. Adverse effects should not be different from those observed for the OD. Adverse effects observed when the GD is used must be notified, as is the case for the OD. Accountability is established according to 4 essential pieces of information: a prescriber, a patient, a drug, and an adverse effect. It is sometimes difficult to identify the provider of the GD that has been delivered.

CONCLUSION

The level of safety concerning effectiveness and tolerance required is identical for OD and GD, in Europe. Analyzing confirmed adverse effects and therapeutic failures is the only way to identify differences that could question a GD's effectiveness.

Generic products of antiepileptic drugs: a perspective on bioequivalence, bioavailability, and formulation switches using Monte Carlo simulations

INTRODUCTION

Generic products of antiepileptic drugs (AEDs) are currently a controversial topic as neurologists and patients are reluctant to switch from brand products to generics and to switch between generics.

OBJECTIVE

The aim of this study was to provide enlightenment on issues of bioequivalence (BE) and interchangeability of AED products.

METHODS

Monte Carlo simulations of the classic 2 × 2 BE studies were performed to study the effect of sample size, within-subject variability, and the true difference in pharmacokinetic values of the products under comparison on BE acceptance of generic AED products. Simulations were extended to study the comparative performance of two generic AED products against the same innovative product. The simulated results are compared with literature data on AEDs.

RESULTS

The question with regard to bioavailability (BA) is whether two formulations are different, while for BE the question is whether two formulations are sufficiently similar in terms of extent and rate of absorption. Therefore, the criteria for BA and BE and the statistical analysis involved in their analysis are different. Two generic formulations that meet regulatory approval requirements for generics by being bioequivalent to the same innovative AED may not be bioequivalent to one another and therefore should not be regarded as equal or as therapeutically equivalent products. A switch from a standard or an immediate-release formulation to a modified-release product, which comprises extended-release or delayed-release formulations, should not be regarded as a switch between generics, but rather as a switch between different formulation types.

DISCUSSION

Switches between bioequivalent generic AED products could potentially lead to larger changes in plasma levels and exposure than the brand-to-generic switch. The simulation work verified the clinical findings that not all generic AED products bioequivalent to the same innovative product are bioequivalent to one another.

CONCLUSIONS

Two generic formulations that meet regulatory approval requirements for generics, by being bioequivalent to the innovative AED, may not be bioequivalent to one another. Additional BE criteria are needed for a formulation switch, particularly in epilepsy, where a breakthrough seizure may change a patient's status from seizure-free to refractory.

Generic drugs for hypertension: are they really equivalent?

Many antihypertensive drugs are now available in generic formulations at fractions of the cost of their branded counterparts. In the United States, marketing approval for generic medications is usually granted by the Food and Drug Administration on the basis of two simple studies involving dissolution rates and bioavailability in 24 - 36 healthy people, without data regarding antihypertensive efficacy, safety, or long-term outcomes. This process leaves many true disciples of "Evidence-Based Medicine" in a quandary: prescribe only brand-name medications that have been demonstrated in clinical trials to both lower blood pressure and prevent cardiovascular events, or instead recommend lower-priced generic agents that are usually supported by no such data. This review summarizes the current evidence that generic antihypertensive drugs are likely to be safe and effective, may increase the probability of medication availability and adherence for many patients, but, by law, must have a different physical appearance than the original product.

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 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.

[Special considerations in generic substitution of immunosuppressive drugs in transplantation]

Long-term success in solid organ transplantation strongly depends on the optimal use of maintenance immunosuppressive treatment. Cyclosporin and tacrolimus are the most frequently administered immunosuppressants and they are designed to narrow therapeutic index drugs. The substitution of the branded formulation by their generic counterparts may lead to economic benefit only if equivalent clinical outcomes can be achieved. There is no published evidence to date on the guarantee of their long-term therapeutic equivalence and cases of therapeutic failures have been reported due to inadvertent drug conversion. The disadvantageous clinical consequences of a non medical, mechanistic forced switch from the original to generic formulation of tacrolimus and the estimated loss of the payer's presumed savings are presented in a kidney transplant recipient population. Special problems related to pediatric patients, drug interactions with concurrent medications and the burden of additional therapeutic drug monitoring and follow up visits are also discussed. The authors are convinced that the implementation of the European Society of Organ Transplantation guidelines on generic substitution may provide a safe way for patients and healthcare payers.

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

BACKGROUND

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

OBJECTIVE

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

STUDY DESIGN

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Host factors affecting antiepileptic drug delivery-pharmacokinetic variability

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

Clinical outcomes associated with brand-to-generic phenytoin interchange

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Deficiencies of the FDA in evaluating generic formulations: addressing narrow therapeutic index drugs

Generic drugs represent a significant portion of the medical arsenal in treating disease. As copies of originator drugs, these drugs have been permitted abbreviated approval under the Hatch-Waxman Act. Yet with the current cost focus upon generic formulations, potential safety issues with generics have arisen. Although there is an established criterion of "bioequivalence" that generic formulations must demonstrate, narrow-therapeutic index drugs for sensitive clinical circumstances such as epilepsy, antiplatelet therapies, and mental health treatments may require different regulatory treatment than other generic drugs. Further, in these circumstances, differences in generic formulations may lead to adverse clinical outcomes due to less stringent bioequivalence tolerances. Yet there is no mandate for comparison between different generic formulations. Countries outside the United States advocate for narrowing tolerance ranges for these high risk health situations and the drugs for their treatment. We argue in this paper that additional patient safety matters must be taken into account for narrow therapeutic disease drugs, and regulatory bodies should emphasize greater tightness in bioequivalence before these narrow-therapeutic drug generic formulations are approved.

Generic Substitution of Antiepileptic Drugs: A Systematic Review of Prospective and Retrospective Studies

Objective:

To systematically review the literature on generic antiepileptic drugs (AEDs), evaluate the efficacy and safety of generic AED substitution, and perform pharmacokinetic (PK) analysis using the American Academy of Neurology (AAN) scheme to classify evidence.

Data Sources:

PubMed and Cumulative Index to Nursing and Allied Health Literature searches from January 1, 1980, to October 15, 2010, were performed using the search terms anticonvulsant, antiepileptic drug, carbamazepine, divalproex, ethosuximide, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, phénobarbital, Phenytoin, primidone, topiramate, valproate, valproic acid, and zonisamide; bioavailability, bioequivalence, bioequivalency, bioequivalent, and substitution; and generic.

Study Selection and Data Extraction:

Retrospective and prospective controlled studies of generic substitution of AEDs were included in the review. Non-English-language articles and uncontrolled clinical studies were excluded, Published articles were categorized using the AAN criteria for systematic reviews.

Data Synthesis:

We identified 156 articles. Of these, 20 met our inclusion criteria; 7 were retrospective studies, 6 were prospective studies in patients with epilepsy, and 7 were prospective studies in healthy subjects. All articles were rated Class I to Class III, using AAN criteria. The retrospective studies were categorized as Class III and showed a significant relationship between generic substitution and increased use of health care resources because of seizures or AED toxicity. Prospective studies were categorized as Class I, II, and III. Prospective studies in patients showed no differences between brand and generic drugs in PK parameters of bioequivalence. Three prospective studies in healthy subjects reported significant differences in maximum drug concentrations. Comparison of brand and generic drugs revealed no significant difference in seizure frequency; however, some prospective studies showed significant differences in PK parameters, primarily those not used for bioequivalence determinations.

Conclusions:

There is inconsistency between retrospective and prospective studies of generic AED substitution. The highest levels of evidence indicate that there should not be a problem with generic substitution, although some patients are more prone to problems with the generic products. Some evidence suggests that switches between multiple generic AED products in certain individuals may be problematic.