Assessment of potential drug interactions in patients with epilepsy: impact of age and sex.

OBJECTIVES: To understand and quantify the exposure to concomitant medications other than antiepileptic drugs (AEDs) within an age-diverse group of men and women with epilepsy and explore the likelihood of relevant drug interactions as a result.

METHODS: The PharMetrics medical and pharmaceutical claims database was used to extract data for commercially insured adult patients with a diagnosis of epilepsy and treated with any AED during the period from July 1, 2001, to December 31, 2004. Data were analyzed for concomitant non-AEDs used after initiating AEDs in six age groups, spanning the ages 18 to 85+ years, in both men and women.

RESULTS: Use of concomitant medications occurred in every age group and increased with age for both men and women (mean number of non-AEDs ranging from 2.41 to 7.67 in males aged 18-34 and 85+ years and from 4.04 to 7.05 in females aged 18-34 and 85+ years; p < 0.001 for age trend). beta-Hydroxy-beta-methylglutaryl-coenzyme A reductase inhibitors (statins), calcium channel blockers (CCBs), and selective serotonin reuptake inhibitors (SSRIs) were the most commonly used non-AED medications with the potential for adverse drug interactions. SSRIs use was substantial in all age groups and greater than for statins or CCBs in patients aged 18-54 years. Use of antipsychotics, tricyclic antidepressants, and warfarin was also noted in more than 10% of patients across different age groups.

CONCLUSIONS: Polypharmacy with non-antiepileptic drug (AED) medications is common in both men and women, and is not a situation unique to only elderly patients with epilepsy. In particular, use of potentially interacting, enzyme inducing AEDs was common. These findings suggest that clinicians must be mindful of potential AED-non-AED drug interactions, in patients of all age groups.