Abstracts

Rationale: Approximately 6% to 10% of elderly nursing home residents have a diagnosis of epilepsy.1 These patients take multiple comedications which have the potential for drug interactions.2 Comedications that can interact with the hepatic metabolism of AEDs are antidepressants, antipsychotics, proton pump inhibitors, statins, calcium channel blockers (CCB), clopidogrel, and warfarin. This study aimed to explore the medications taken by patients with epilepsy in nursing homes to evaluate the frequency of potential drug interactions between the comedications and antiepileptic drugs (AED). Methods: A prospective trial was conducted among 121 elderly nursing home patients to study the use of drugs classified as AEDs. This study was approved by the University of Minnesota s Institutional Review Board. Nursing home residents who were 60 years or older and who were taking one of the four AEDs (phenytoin, levetiracetam, lamotrigine, gabapentin) were identified from 2007 to 2013. Only those with a diagnosis of epilepsy were included in this presentation. All comedications, except vitamins and nutritional supplements, were explored in this study. The order records at the nursing homes were reviewed and drugs prescribed were entered into the study database. The total number of drugs used by each patient was compiled, and frequencies of use by drug class were calculated.Results: Of 121 patients, 37 had a diagnosis of epilepsy. In these, phenytoin was used in 21 (56.8%) patients, levetiracetam in 13 (35.1%), gabapentin in 2 (5.4%), and lamotrigine in 1 (2.7%) patient. The average number of comedications was 14 per patient. Comedications which interact were used as follows: antidepressants by 22 (59.5 %) patients, atypical antipsychotics by 8 (21.6%), proton pump inhibitors by 18 (48.6%), statins by 12 (32.4%), CCBs by 5 (13.5%), clopidogrel by 5 (13.5%), and warfarin by 5 (13.5%) patients. Other common comedications that do not interact with the hepatic metabolism of AEDs were antihypertensive drugs other than CCBs (22; 59.5%) and aspirin (22; 59.5%). Overall, out of total 37 patients, at least 21 (56.8%) patients had one or more comedications that can interact with the hepatic metabolism of phenytoin or lamotrigine. Conclusions: The most commonly used AED was phenytoin which is metabolized by cytochrome P450 2C9 and 2C19. Its frequency of use was similar to the 60% of all AEDs reported during the 1990s.1 The riskiest interaction is a combination of phenytoin and warfarin but the effectiveness of the others, especially the statins, may be reduced. Lamotrigine is glucuronidated and may have a significant interaction with sertraline. References: 1) Garrard J, Harms S, Hardie N, Eberly LE, Nitz N, Bland P, Gross CR, Leppik IE. Antiepileptic drug use in nursing home admissions. Annals of Neurology 2003:54:75-85. 2) Cloyd JC, Lackner TE, Leppik IE. Antiepileptic drugs in the elderly: pharmacoepidemiology and pharmacokinetics. Arch Fam Med 1994;3:589-598. Funded by NIH NIA 1R01AG026390