Background: Phenytoin (PHT) dosing regimens are often determined based on experience in those aged <65 years rather than in those aged ≥65 years. Objective: The goal of this study was to determine the impact of sex, age, receipt of concomitant inhibitors or inducers of PHT metabolism, and albumin levels on doses and total serum concentrations of PHT in elderly nursing home residents. Methods: Consulting pharmacists to nursing homes located throughout the United States collected data from June 1998 to December 2000. The mean daily dose per person and mean total serum PHT concentration were tested for statistical differences by sex, age group (65-74, 75-84, and ≥85 years), coadministration of PHT inhibitors or inducers, and albumin levels. Results: Data were collected from 387 residents (259 women, 128 men) of 112 nursing homes in 19 states who received PHT and for whom PHT concentrations were available. The mean (SD) age of the study population was 79.4 (7.8) years; women constituted 67.0% of the study population. The mean (SD) total daily dose and total PHT concentration were 4.9 (1.8) mg/kg and 11.7 (6.4) mg/L, respectively. In general, women received higher mean (SD) daily doses of PHT compared with men (5.1 [1.8] vs 4.6 [1.6] mg/kg, respectively; P = 0.017) to achieve similar total serum concentrations (11.6 [6.4] and 12.0 [6.6] mg/L). PHT doses and serum concentrations were similar between age groups. There were no differences in daily doses (mg/kg or mg/d) or total serum concentrations of PHT based on concomitant use of inhibitors or inducers of PHT metabolism or on albumin levels. Conclusions: In this study in elderly nursing home residents, women received higher doses of PHT than men to achieve similar total serum PHT concentrations. There were no differences in doses or total serum PHT concentrations by age group, use of concomitant inducers or inhibitors of PHT metabolism, or albumin levels.
Bibliographical noteFunding Information:
This work was supported by NIH NINDS P50-NS16308. The authors thank PharMerica pharmacists for aiding in the abstraction of data and Beverly Enterprises, Inc., for allowing the participation of their nursing homes.
- Nursing home