A Trial of Generic Substitution of Antiepileptic Drugs

Summary

Background. Anecdotal reports and uncontrolled studies have described an association between generic substitution of antiepileptic drugs (AEDs) and adverse events, including loss of seizure control. Although these results are likely to be influenced by methodological bias, they have led to a strong opposition, among physicians and patients, to the use of generic products in epilepsy. Objectives. The primary objective is to assess potential risks associated with substitution of the currently taken AED product with an equivalent product, using as endpoint changes in serum drug levels at steady-state after substitution compared with baseline. Secondary objectives will be the assessment of inter-subject variability in serum drug concentration on an unchanged treatment schedule, and evaluation of potential short-term changes in seizure control and adverse events rate. Methods. The study will use an experimental randomized open-label non-inferiority design. The population will consist of 200 adults stabilized on chronic treatment with carbamazepine, valproic acid, topiramate, oxcarbazepine, levetiracetam or lamotrigine and admitted to hospital for diagnostic evaluation or other indications, with no expected treatment changes during the subsequent 5 to 6 days. Patients will be randomized to two groups. One group will continue to receive the AED products used before enrollment (brand or generic), whereas the other group will be switched to an alternative equivalent product. Dosing schedules of the AEDs being tested as well as comedications will be unaltered throughout the 6- to 7day period of the study. Serum AED levels (mean of two values obtained at peak and trough, respectively in the evening and the next morning) will be measured on day 1 (baseline) and 5 days post-randomization (6 days for patients receiving AEDs with half-lives above 12 h). The primary outcome endpoint will be the proportion of patients who, post-randomization, show a greater than 25% change in serum drug concentration compared with baseline. Secondary endpoints will include comparison of distributions of rough serum concentration changes between groups, other pharmacokinetic parameters, time to first seizure, total number of seizures, and adverse events.

Timeline

Start

2012-05

Primary completion

2015-05

Completion

2015-05

Publications

• Background Andermann F, Duh MS, Gosselin A, Paradis PE. Compulsory generic switching of antiepileptic drugs: high switchback rates to branded compounds compared with other drug classes. Epilepsia. 2007 Mar;48(3):464-9. doi: 10.1111/j.1528-1167.2007.01007.x.
• Background Baker GA, Jacoby A, Buck D, Stalgis C, Monnet D. Quality of life of people with epilepsy: a European study. Epilepsia. 1997 Mar;38(3):353-62. doi: 10.1111/j.1528-1157.1997.tb01128.x.
• Background Bartoli A, Marchiselli R, Gatti G. A rapid and specific assay for the determination of lamotrigine in human plasma by normal-phase HPLC. Ther Drug Monit. 1997 Feb;19(1):100-7. doi: 10.1097/00007691-199702000-00020.
• Background Berg MJ, Gross RA, Tomaszewski KJ, Zingaro WM, Haskins LS. Generic substitution in the treatment of epilepsy: case evidence of breakthrough seizures. Neurology. 2008 Aug 12;71(7):525-30. doi: 10.1212/01.wnl.0000319958.37502.8e.
• Background Berg MJ, Gross RA, Haskins LS, Zingaro WM, Tomaszewski KJ. Generic substitution in the treatment of epilepsy: patient and physician perceptions. Epilepsy Behav. 2008 Nov;13(4):693-9. doi: 10.1016/j.yebeh.2008.06.001. Epub 2008 Sep 10.
• Background Bialer M, Midha KK. Generic products of antiepileptic drugs: a perspective on bioequivalence and interchangeability. Epilepsia. 2010 Jun;51(6):941-50. doi: 10.1111/j.1528-1167.2010.02573.x. Epub 2010 Apr 8.
• Background Kramer G, Biraben A, Carreno M, Guekht A, de Haan GJ, Jedrzejczak J, Josephs D, van Rijckevorsel K, Zaccara G. Current approaches to the use of generic antiepileptic drugs. Epilepsy Behav. 2007 Aug;11(1):46-52. doi: 10.1016/j.yebeh.2007.03.014. Epub 2007 May 29.
• Background Labiner DM, Paradis PE, Manjunath R, Duh MS, Lafeuille MH, Latremouille-Viau D, Lefebvre P, Helmers SL. Generic antiepileptic drugs and associated medical resource utilization in the United States. Neurology. 2010 May 18;74(20):1566-74. doi: 10.1212/WNL.0b013e3181df091b. Epub 2010 Apr 14.
• Background Kesselheim AS, Stedman MR, Bubrick EJ, Gagne JJ, Misono AS, Lee JL, Brookhart MA, Avorn J, Shrank WH. Seizure outcomes following the use of generic versus brand-name antiepileptic drugs: a systematic review and meta-analysis. Drugs. 2010 Mar 26;70(5):605-21. doi: 10.2165/10898530-000000000-00000.
• Background Perucca E, Albani F, Capovilla G, Bernardina BD, Michelucci R, Zaccara G. Recommendations of the Italian League against Epilepsy working group on generic products of antiepileptic drugs. Epilepsia. 2006;47 Suppl 5:16-20. doi: 10.1111/j.1528-1167.2006.00871.x.
• Background Privitera MD. Generic antiepileptic drugs: current controversies and future directions. Epilepsy Curr. 2008 Sep-Oct;8(5):113-7. doi: 10.1111/j.1535-7511.2008.00261.x.
• Background Zachry WM 3rd, Doan QD, Clewell JD, Smith BJ. Case-control analysis of ambulance, emergency room, or inpatient hospital events for epilepsy and antiepileptic drug formulation changes. Epilepsia. 2009 Mar;50(3):493-500. doi: 10.1111/j.1528-1167.2008.01703.x. Epub 2008 Jun 26.
• Background Wilner AN. Therapeutic equivalency of generic antiepileptic drugs: results of a survey. Epilepsy Behav. 2004 Dec;5(6):995-8. doi: 10.1016/j.yebeh.2004.05.011.

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