U of M College of Pharmacy Study Finds Common Epilepsy Drug Lasts Longer and May Require Fewer Doses in Elderly Patients Than Previously Assumed

Finding could reduce medication administration costs in nursing homes

MINNEAPOLIS / ST. PAUL (July 7, 2008) — A new University of Minnesota College of Pharmacy study found that phenytoin (PHT), an anti-seizure medication widely prescribed to treat epilepsy in elderly patients, may require fewer daily doses than previously reported.

The study, published in the current issue of the journal Neurology, followed 63 adults with epilepsy (45 of whom were 65 years or older) to determine if age and sex affected how PHT worked in the body. Previous studies have indicated aging is associated with many factors that can affect how PHT is absorbed, distributed, and metabolized in the body. The research showed that the time it takes the body to eliminate half of a dose of PHT is longer in older patients.

“Determining what effects age has on how PHT works will help us to more safely and effectively treat all patients with epilepsy,” said James Cloyd, Pharm.D., professor, Lawrence C. Weaver Endowed Chair -- Orphan Drug Development, and principal investigator of the study. “We found that age and sex do not have a significant effect on PHT elimination, but PHT half life is much longer in both adults and elderly than previously assumed.”

According to Cloyd, the longer half life allows most adults to take PHT once daily, in contrast to the typical recommendation that the drug be taken two to three times daily.

“Once daily dosing can improve medication compliance and, in nursing homes, reduce medication administration costs,” Cloyd said.

Study participants received a single injection of a stable-labeled (non-radioactive) isotope of PHT followed by their usual oral PHT dose. Blood samples were then collected and analyzed. PHT concentrations of both the labeled and the regular PHT were followed for up to eight days after the dose.

Cloyd cautions that this study’s participants were relatively healthy and did not reflect older patients who are less healthy or take multiple medications. He recommended further studies of PHT in more complicated patients, such as the frail elderly with medical problems.

The study, funded by a grant from the National Institutes of Health’s National Institute of Neurological Disorders and Stroke, was conducted by researchers at the University of Minnesota’s College of Pharmacy and Medical School, MINCEP Epilepsy Care, and the University of Miami.

The College of Pharmacy, the only school of pharmacy in Minnesota, offers its program on the Twin Cities and Duluth campuses. Founded in 1892, the College of Pharmacy educates pharmacists and scientists and engages in research and practice to improve the health of the people of Minnesota and society. The college is part of the Academic Health Center, which is home to the University of Minnesota’s six health professional schools and colleges as well as several health-related centers and institutes. Learn more at www.pharmacy.umn.edu.

Contact: Amy Leslie, College of Pharmacy, 612-624-7654
Sara E. Buss, Academic Health Center, 612-626-7037