Pharmacokinetic Factors to Consider in the Selection of Antiseizure Drugs for Older Patients with Epilepsy

The incidence of epilepsy is highest in the older adult age group. Seizures in older adults can be more difficult to diagnose because their presentation is often subtle and can easily be mistaken for other conditions. Fortunately, new-onset epilepsy in the older adult is often pharmaco-responsive, with as many as 80-85% of patients achieving remission, often with monotherapy at modest doses. Many physiological and pathological changes occur with aging that can alter the pharmacokinetics of antiseizure drugs (ASDs). For the majority of the old- and new-generation ASDs, a decrease in dose may be needed to maintain concentrations equivalent to those found in young adults. The risk of drug interactions with ASDs is substantial, as polypharmacy is common. The first-generation ASDs (carbamazepine, phenytoin, phenobarbital, and valproic acid) have the potential to interact with many drugs, but many newer ASDs either do not have significant interactions or are selective inhibitors and inducers of specific hepatic enzymes. The differences in adverse effects between younger and older adults are not just due to dosing and pharmacokinetics. Older adults are more susceptible to the gait, balance, and cognitive effects of ASDs. Overall, the improved tolerability and decreased drug interaction potential of the newer-generation ASDs, such as lamotrigine and levetiracetam, have demonstrated their superiority in the treatment of seizures in older adults and, as such, are clearly favored for new-onset epilepsy in older adults.