title: Generic-to-generic lamotrigine switches in people with epilepsy: the randomised controlled EQUIGEN trial.
abstract: BACKGROUND
  Patients and clinicians share concerns that generic drug substitution might lead to loss of efficacy or emergence of adverse events. In this trial, we assessed US Food and Drug Administration (FDA) bioequivalence standards by studying the effects of switching between two disparate generic immediate-release lamotrigine products in patients with epilepsy.
  
  
  METHODS
  The Equivalence among Generic Antiepileptic Drugs (EQUIGEN) chronic-dose study was a randomised, double-blind, crossover study that enrolled adults (aged ≥18 years) with epilepsy from six epilepsy centres at academic institutions across the USA who were receiving immediate-release lamotrigine dosed at 100 mg, 200 mg, 300 mg, or 400 mg twice daily. Eligible patients were randomly allocated (1:1) to one of two treatment sequences (sequence 1 or sequence 2), comprising four study periods of 14 days each. During each 14-day treatment period, patients received balanced doses of an oral generic lamotrigine product every 12 h (200-800 mg total, identical to lamotrigine dose prior to study enrolment); after each 14-day period, patients were crossed over to receive the other generic product. Computer-based randomisation was done using random permuted blocks of size two or four for each site to prevent sequence predictability. Both patients and study personnel were masked to the generic products selected, their predicted exposure (ie, "high" vs "low"), and their group allocation. The primary outcome of this trial was bioequivalence between the generic products, which was assessed at the end of the study through a comparison of maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) for each product in the analysis population (all patients who completed all four treatment periods). Bioequivalence was established if the 90% CIs of the ratios of these two parameters for the two products were within equivalence limits (80-125%) in the analysis population. This study is registered with ClinicalTrials.gov\, number NCT01713777.
  
  
  RESULTS
  Between April 25, 2013, and Aug 12, 2014, 35 eligible patients were enrolled and randomly assigned to treatment sequence 1 (n=15) or treatment sequence 2 (n=20). 33 patients completed all four treatment periods and were included in the primary outcome analysis. The 90% CIs of the ratios of both Cmax and AUC were within equivalence limits (AUC 90% CI 98-103, Cmax 90% CI 99-105), showing that lamotrigine exposures were equivalent between the generic products. No significant changes in seizure frequency or adverse events were recorded. No deaths, study-related serious adverse events, or changes in clinical laboratory values or vital signs occurred during this study.
  
  
  CONCLUSIONS
  Disparate generic lamotrigine products in patients with epilepsy showed bioequivalence with no detectable difference in clinical effects, confirming that US Food and Drug Administration bioequivalence standards are appropriate.
  
  
  BACKGROUND
  American Epilepsy Society, Epilepsy Foundation, and US Food and Drug Administration.
authors.affiliation: University of Cincinnati Medical Center, Cincinnati, OH, USA. Electronic address: privitmd@ucmail.uc.edu.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Privitera
authors.affiliation: College of Pharmacy and Health Sciences, Drake University, Des Moines, IA, USA.
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Welty
authors.affiliation: University of Wisconsin-Madison School of Pharmacy and Department of Neurology, Madison, WI, USA.
authors.forename: Barry E
authors.initials: BE
authors.lastname: Gidal
authors.affiliation: Department of Biostatistics, The University of Kansas Medical Center, Kansas City, KS, USA.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Diaz
authors.affiliation: Department of Biostatistics, The University of Kansas Medical Center, Kansas City, KS, USA.
authors.forename: Ron
authors.initials: R
authors.lastname: Krebill
authors.affiliation: Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: Jerzy P
authors.initials: JP
authors.lastname: Szaflarski
authors.affiliation: Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Dworetzky
authors.affiliation: Department of Neurology; University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Pollard
authors.affiliation: Zeeh Pharmaceutical Experiment Station, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Edmund J
authors.initials: EJ
authors.lastname: Elder
authors.affiliation: Office of Research and Standards, Office of Generic Drugs, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Wenlei
authors.initials: W
authors.lastname: Jiang
authors.affiliation: Office of Research and Standards, Office of Generic Drugs, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Department of Neurology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
authors.forename: Michel
authors.initials: M
authors.lastname: Berg
mesh_terms: D000328:Adult; D000927:Anticonvulsants / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D057915:Drug Substitution / Q000009:adverse effects / Q000592:standards*; D016568:Drugs, Generic / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology*; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D006801:Humans; D000077213:Lamotrigine; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D013810:Therapeutic Equivalency; D014227:Triazines / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology*; D014481:United States; D014486:United States Food and Drug Administration / Q000592:standards*
chemical_list: D000927:Anticonvulsants; D016568:Drugs, Generic; D014227:Triazines; D000077213:Lamotrigine