Abstracts

Switching patients from older branded antiepileptic drugs (AEDs) to generic versions can increase the risk of breakthrough seizures and side-effects.¹ Less is known about the consequences of substituting newer AEDs for generic compounds.¹ Given the unique challenges in epilepsy treatment and the common concomitant use of narrow therapeutic index epilepsy medications generic substitution for brand-name AEDs may sacrifice efficacy, tolerability, and safety.² Though generic drugs are considered bioequivalent to brand names, clinically relevant differences in drug absorption and availability can occur and produce loss of seizure control or toxicity.² In the current investigation, outcomes associated with substituting one of the first newer AED to become generically available in Canada were assessed for signals warranting further investigation., The impact of generic lamotrigine in epilepsy patients was assessed using reports of lamotrigine-linked adverse reactions filed to Health Canada[apos]s Adverse Drug Reaction Monitoring Program (CADRMP), a survey of pharmacists, and a physician chart audit. It was hypothesized that utilization of generic lamotrigine may be associated with a change in lamotrigine-associated adverse reactions. To test this, lamotrigine-related adverse reactions reported to the CADRMP over identical periods before (baseline period) and after (study period) generic lamotrigine became available were compared., Reports of lamotrigine-associated adverse reactions to CADRMP rose from 30 during the baseline period to 56 in the study period. Over the latter period 29 of the 56 reports (52%) were linked to generic lamotrigine (versus 23% over the baseline period), 14 of which involved lack of seizure control. Loss of seizure control was the primary reason patients were switched back to Lamictal^[reg] in the pharmacists[apos] survey (11/14 patients) and the physicians chart audit (8/9 patients). Seizure control was regained for the majority of patients following a return to branded lamotrigine., These initial reports of loss of seizure control in some patients following brand-to-generic Lamotrigine switching, build upon existing similar experiences with older AEDs. The results of this study suggest that (i) seizure control can be compromised when switching from Lamictal^[reg] to generic lamotrigine, and (ii) lamotrigine-associated adverse reactions increased after generic lamotrigine was prescribed. These data stress the vital role physicians play in educating their patients as to the potential risks and benefits of AED generic substitution.

¹ Crawford P, Hall WW, Chappell B, et al. Generic prescribing for epilepsy. Is it safe? [italic]Seizure[/italic] 1996;:1-5.
² Guberman A, Corman C. Generic substitution for brand name antiepileptic drugs: a survey. [italic]Can J Neurol Sci[/italic] 2000;:37-43., (Supported by a grant from GlaxoSmithKline Inc.)