Compulsory generic switching of antiepileptic drugs: high switchback rates to branded compounds compared with other drug classes.
OBJECTIVE
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.
Andermann
Frederick
F
Montreal Neurological Institute and Hospital, McGill University, Montréal, Québec, Canada. andermannf@qc.aibn.com
Duh
Mei Sheng
MS
Gosselin
Antoine
A
Paradis
Pierre Emmanuel
PE
D000293:Adolescent; D000328:Adult; D000927:Anticonvulsants / Q000493:pharmacokinetics / Q000627:therapeutic use*; D002648:Child; D015331:Cohort Studies; D003362:Cost-Benefit Analysis; D016527:Drug Costs; D011307:Drug Prescriptions / Q000191:economics / Q000592:standards / Q000706:statistics & numerical data*; D004359:Drug Therapy, Combination; D016568:Drugs, Generic / Q000493:pharmacokinetics / Q000627:therapeutic use*; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D006801:Humans; D007356:Insurance, Pharmaceutical Services / Q000331:legislation & jurisprudence / Q000706:statistics & numerical data; D053208:Kaplan-Meier Estimate; D000077213:Lamotrigine; D008297:Male; D009864:Ontario; D010342:Patient Acceptance of Health Care; D013810:Therapeutic Equivalency; D016896:Treatment Outcome; D014227:Triazines / Q000627:therapeutic use
D000927:Anticonvulsants; D016568:Drugs, Generic; D014227:Triazines; D000077213:Lamotrigine