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Elmer S, Reddy DS. Therapeutic Basis of Generic Substitution of Antiseizure Medications. J Pharmacol Exp Ther 2022; 381:188-196. [PMID: 35241634 PMCID: PMC9132097 DOI: 10.1124/jpet.121.000994] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 02/25/2022] [Indexed: 11/22/2022] Open
Abstract
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.
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Affiliation(s)
- Sarah Elmer
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, Texas
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Frade VP, Paiva MJND, Martins I, Castro WVD, Belo VS, Baldoni AO, Lima PDF, Sanches C. Interchangeability among carbamazepine formulations: the impact over epilepsy patients. BRAZ J PHARM SCI 2022. [DOI: 10.1590/s2175-97902022e19594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Giometto S, Baglietto L, Conte M, Vannacci A, Tuccori M, Mugelli A, Gini R, Lucenteforte E. Use of antiseizure medications and safety of branded versus generic formulations: A comparative study on Tuscan administrative databases. Epilepsy Behav 2021; 117:107876. [PMID: 33714929 DOI: 10.1016/j.yebeh.2021.107876] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/14/2021] [Accepted: 02/18/2021] [Indexed: 11/19/2022]
Abstract
PURPOSE To assess patterns of use of antiseizure medications (ASMs) and to compare the safety of generic versus branded formulations in terms of admission to hospital or to emergency department (ED). METHODS We conducted a drug utilization study with a propensity score-matched design using the administrative databases of the Italian Tuscany region. New users of ASMs during 2015 with no history of neoplasia were considered and their first prescription was classified as: available only as branded (only-B-ASM); branded with generic available (B-ASM); and generic (G-ASM). Patients with G-ASM first prescription were matched with four patients with B-ASM prescription. Participants were followed up for one year or until the date of death or diagnosis of neoplasia. Cox regression models were fitted to estimate the risk of admission to hospital or ED. RESULTS We identified 36,601 ASM new-users, including 2094 (6.4%) with only-B-ASM as first prescription, 24,588 (74.9%) with B-ASM, and 5788 (17.6%) with G-ASM. We found no differences in the risk of admission to hospital or ED (Hazard Ratio (HR), 0.92; 95% Confidence Interval (CI), 0.85-1.02) among users of generic ASMs compared to those using branded ASMs. CONCLUSIONS In our study population, generic ASMs were used less than branded ones. The similarity in the safety of branded and generic formulations suggests that generic ASMs could be the preferred formulation in current clinical practice resulting in a substantial decrease in the cost of treatment.
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Affiliation(s)
- Sabrina Giometto
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy.
| | - Laura Baglietto
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy.
| | - Marco Conte
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
| | - Alfredo Vannacci
- Department of Neurosciences, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Florence, Italy.
| | - Marco Tuccori
- Unit of Pharmacology and Pharmacovigilance, Department of Clinical and Experimental Medicine, University Hospital of Pisa, Pisa, Italy
| | - Alessandro Mugelli
- Department of Neurosciences, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Florence, Italy.
| | - Rosa Gini
- Agenzia regionale di sanità della Toscana, Florence, Italy.
| | - Ersilia Lucenteforte
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy.
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Effects of generic exchange of solid oral dosage forms in neurological disorders: a systematic review. Int J Clin Pharm 2020; 42:393-417. [PMID: 32274633 DOI: 10.1007/s11096-020-01023-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 03/30/2020] [Indexed: 10/24/2022]
Abstract
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 (cmax) or the time at which cmax is observed (tmax). 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.
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Kim H, Fang L, Yu J, Meng Z, Trame MN, Schmidt S, Lesko LJ, Zhao L. Is Bioequivalence Established Based on the Reference-Scaled Average Bioequivalence Approach Relevant to Chronic Administration of Phenytoin? Perspectives Based on Population Pharmacokinetic Modeling and Simulations. J Clin Pharmacol 2019; 59:1061-1069. [PMID: 30716169 DOI: 10.1002/jcph.1380] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 01/04/2019] [Indexed: 01/14/2023]
Abstract
Phenytoin demonstrates time-dependent and nonlinear pharmacokinetics (PK) within the therapeutic range of 10 to 20 μg/mL. There are discussions on the relevance of bioequivalence (BE) demonstrated in a single-dose BE study in healthy subjects to exposure under chronic use conditions in patients, particularly given that phenytoin has a narrow therapeutic index. The objective of this study was to quantitatively evaluate the appropriateness of single-dose PK BE through simulations for the phenytoin extended-capsule products. A previously published population PK model was updated to account for the interoccasion variability using the dense PK data of the reference listed drug (Dilantin) from 5 single-dose, fully replicated BE studies (n = 124). BE studies with alternative designs were simulated using the developed PK model and subsequently analyzed accordingly: Scenario 1, multiple-dose, 2-period, crossover BE studies with an average BE approach; Scenario 2, single-dose, 4-period, fully replicated BE studies with a reference-scaled average BE approach as recommended in the product-specific guidance. In both scenarios, hypothetical phenytoin capsules with different formulation-related PK parameters, such as relative bioavailability and absorption rates, were included in the simulations. The results showed that the both scenarios provided the same results with respect to BE conclusions.
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Affiliation(s)
- Hyewon Kim
- Office of Research and Standards, Office of Generic Drugs, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Lanyan Fang
- Office of Research and Standards, Office of Generic Drugs, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Jingyu Yu
- Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Zhaoyu Meng
- Center for Pharmacometrics and Systems Pharmacology, Department of Pharmaceutics, College of Pharmacy, University of Florida, Orlando, FL, USA
| | - Mirjam N Trame
- Center for Pharmacometrics and Systems Pharmacology, Department of Pharmaceutics, College of Pharmacy, University of Florida, Orlando, FL, USA
| | - Stephan Schmidt
- Center for Pharmacometrics and Systems Pharmacology, Department of Pharmaceutics, College of Pharmacy, University of Florida, Orlando, FL, USA
| | - Lawrence J Lesko
- Center for Pharmacometrics and Systems Pharmacology, Department of Pharmaceutics, College of Pharmacy, University of Florida, Orlando, FL, USA
| | - Liang Zhao
- Office of Research and Standards, Office of Generic Drugs, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
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Trimboli M, Russo E, Mumoli L, Tripepi G, Fortunato F, Mastroianni G, Abate F, De Sarro G, Gambardella A, Labate A. Brand-to-generic levetiracetam switching: a 4-year prospective observational real-life study. Eur J Neurol 2018; 25:666-671. [DOI: 10.1111/ene.13568] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 12/27/2017] [Indexed: 11/29/2022]
Affiliation(s)
- M. Trimboli
- Department of Medical Sciences; Institute of Neurology; University Magna Graecia; Catanzaro Italy
| | - E. Russo
- Science of Health Department; School of Medicine; University Magna Graecia; Catanzaro Italy
| | - L. Mumoli
- Department of Medical Sciences; Institute of Neurology; University Magna Graecia; Catanzaro Italy
| | - G. Tripepi
- Institute of Clinical Physiology; Research Unit of Reggio Calabria; National Research Council (IFC-CNR); Reggio Calabria Italy
| | - F. Fortunato
- Department of Medical Sciences; Institute of Neurology; University Magna Graecia; Catanzaro Italy
| | - G. Mastroianni
- Department of Medical Sciences; Institute of Neurology; University Magna Graecia; Catanzaro Italy
| | - F. Abate
- Department of Medical Sciences; Institute of Neurology; University Magna Graecia; Catanzaro Italy
| | - G. De Sarro
- Science of Health Department; School of Medicine; University Magna Graecia; Catanzaro Italy
| | - A. Gambardella
- Department of Medical Sciences; Institute of Neurology; University Magna Graecia; Catanzaro Italy
| | - A. Labate
- Department of Medical Sciences; Institute of Neurology; University Magna Graecia; Catanzaro Italy
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Kwan P, Palmini A. Association between switching antiepileptic drug products and healthcare utilization: A systematic review. Epilepsy Behav 2017. [PMID: 28641169 DOI: 10.1016/j.yebeh.2017.05.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
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.
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Affiliation(s)
- Patrick Kwan
- Department of Medicine, The University of Melbourne, Parkville, Victoria, Australia; Department of Neurology, Royal Melbourne Hospital, Parkville, Victoria, Australia.
| | - André Palmini
- Faculty of Medicine, Neurology Service & Porto Alegre Epilepsy Surgery Program, Hospital São Lucas, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, Brazil.
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Intrapatient variation in antiepileptic drug plasma concentration after generic substitution vs stable brand-name drug regimens. Epilepsy Res 2016; 122:79-83. [PMID: 26987080 DOI: 10.1016/j.eplepsyres.2016.02.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 01/21/2016] [Accepted: 02/28/2016] [Indexed: 11/20/2022]
Abstract
Generic substitution of antiepileptic drugs (AEDs) is still a matter of controversy and concern among clinicians and patients. We aimed to assess intrasubject variation in plasma concentrations of lamotrigine (LTG), levetiracetam (LEV) and topiramate (TPM) after generic substitution compared with a stable brand-name drug regimen in a population of patients with epilepsy. A retrospective analysis was performed on prospectively collected and stored data from our therapeutic drug monitoring (TDM) database for the years 2009-2014. The main outcome variable was the proportion of patients who, after switching from branded to generic formulations, showed a greater than ±20% change in AED plasma concentrations compared to the proportion of control patients showing a change in AED plasma concentrations of the same extent while receiving stable branded formulations over repeated TDM tests. Fifty patients on LTG, 27 on LEV and 16 on TPM showing at least one TDM test while receiving generic products fulfilled the inclusion/exclusion criteria for the analysis and were compared with 200 control patients for LTG, 120 for LEV and 80 for TPM. The proportion of patients showing an intrasubject change greater than ±20% in AED plasma concentrations was similar in the brand name vs generic group compared with the control one for LTG (22% vs 33%) and LEV (44% vs 38%), while it was higher in the control group for TPM (41% vs 6%, p<0.01). These are the first data in the literature about the within-patient variation in steady-state plasma concentrations of a series of stable treatments with brand-name AEDs in a real clinical setting. In conclusion, a significant interday variability in intrapatient LTG, LEV and TPM plasma concentrations can be observed even in patients stabilized with the same brand name product over time. This suggests that any change in plasma AED concentration and possible related clinical effects after generic substitution may be not necessarily related to the switch. Our results should be confirmed by large, prospective, blinded, randomized controlled studies in people with epilepsy.
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