Abstracts

Older antiepileptic drugs (AEDs) are associated with an increased potential for drug interactions when compared with newer AEDs (topiramate, lamotrigine, gabapentin, levetiracetam, etc.). However, the frequency with which patients are susceptible to drug-drug interactions in clinical practice is not known. This study compared the frequency of potential clinically relevant drug interactions for newer and older AEDs., In this retrospective, observational study, administrative claims obtained from a state Medicaid program were screened to identify records meeting the following criteria: 1) an AED prescription claim during the enrollment period (September 1, 2003 [ndash] September 30, 2004), defined as the index prescription, for either a newer or older agent; 2) an [italic]International Classification of Disease, Ninth Revision, Clinical Modification[/italic] code for epilepsy; 3) continuous enrollment 12 months after the index prescription. The potential for drug-drug interactions was quantified by the percentage of episodes, regardless of their duration, in which AED exposure coincided with exposure to another non-AED known to have a clinically relevant interaction with the AED.[1]
[1] Perucca E. Clinically relevant drug interactions with antiepileptic drugs. [italic]Br J Clin Pharmacol[/italic]. 2005;61(3):246-255., A total of 756 patients met the inclusion criteria. The average patient age was 34 (SD [plusmn]22) years; 53% (n=400) were female. In this patient population, there were 1,444 exposures to AEDs; 34.9% (n=504) were exposures to new AEDs, and 65.1% (n=940) were exposures to old AEDs. Of the new AED exposures, 2.6% (n=13) coincided with another medication known to have a clinically relevant drug interaction as compared with 55.8% (n=525) of old AED exposures.
[1] Perucca E. Clinically relevant drug interactions with antiepileptic drugs. [italic]Br J Clin Pharmacol[/italic]. 2005;61(3):246-255., This study is the first to document the extent of co-exposure of AEDs with other drugs known to cause drug interaction. Older AEDs are associated with a greater likelihood of a potential clinically relevant drug interaction than a newer AED in this state Medicaid population. Future research documenting the clinical outcomes of these interactions and analysis adjusting for exposure time of each AED is warranted., (Supported by Ortho-McNeil Janssen Scientific Affairs, LLC.)