Nancy A. Hardie

Variability of total phenytoin serum concentrations within elderly nursing home residents.

Background: Approximately 6% of all elderly nursing home residents receive phenytoin. Phenytoin concentrations are often measured to guide therapy. Objective: To evaluate the intraresident variability among multiple measurements of total phenytoin serum concentrations in nursing home residents. Methods: This was an observational study of 56 elderly (≥65 years) nursing home residents from 32 nursing homes who had at least 3 phenytoin concentrations measured while on the same dose of phenytoin for at least 4 weeks and who were not taking any interfering concomitant medications. These were a subset of 387 elderly nursing home residents from 112 nursing homes across the United States who had total phenytoin concentration measurements between June 1998 and December 2000. Results: The mean age was 80.1 years (range, 65 to 100 years) and 58.9% were women. The mean daily dose of phenytoin per resident was 4.9 ± 1.5 mg/kg. Total phenytoin concentrations within an elderly nursing home resident varied as much as two- to threefold, even though there was no change in dose. The person with the smallest variability had a minimum concentration of 10.0 μg/mL and a maximum of 10.4 μg/mL. The person with the largest variability had a minimum concentration of 9.7 μg/mL and a maximum of 28.8 μg/mL. Conclusions: There is considerable variability in the total phenytoin concentrations in the elderly nursing home resident and measurement of a single total phenytoin concentration should not be used to guide treatment.

Antiepileptic drug use in nursing home admissions

Although 1 of 10 nursing home residents is taking an antiepileptic drug (AED), no study to our knowledge has determined whether most residents are already receiving AED treatment when they are admitted or are given these drugs afterward. That differentiation was the focus of this study. The study group consisted of 10,318 residents, 65 years and older, admitted to 510 nursing homes located throughout the United States during the first quarter of 1999. AED prevalence at admission was 7.7%; three fifths had an epilepsy/seizure indication. In a multivariate analysis, factors associated with AED use at admission included epilepsy/seizure, bipolar depression, age group, and cognitive performance. In the follow‐up cohort (N = 9,516), postadmission initiation of AEDs was 2.7%; one fifth had an epilepsy/seizure indication. In the multivariate analysis, factors associated with postadmission AED initiation included epilepsy/seizure indication, bipolar depression, age group, peripheral vascular disease, and cognitive performance. This rate of AED postadmission initiation within the first 3 months of admission was much higher than expected, suggesting that new symptoms may develop after admission. Results also show that the rate of AED use in nursing homes is not static. Ann Neurol 2003;54:000–000

Valproic acid doses, concentrations, and clearances in elderly nursing home residents

VPA daily dose and total VPA concentrations for 146 elderly (> or =65 years) nursing home residents collected from June 1998 to December 2000 in homes located throughout the United States are presented. Average age was 78.5+/-8.0 years old. The mean VPA daily dose was 16.2+/-11.2mg/kg and mean total VPA concentration was 48.5+/-24.8 mg/L. The majority (56.2%) of the VPA residents are being maintained at total VPA levels <50mg/L. Mean daily dose (19.4+/-11.4, 16.3+/-12.1, and 11.3+/-7.6 mg/kg/day; p=0.003) and total VPA concentration (56.4+/-25.8, 47.7+/-22.6, and 38.7+/-23.1mg/kg/day; p=0.003) decreased by age groups (65-74, 75-84, and > or =85 years). Daily dose and total VPA concentration were not different in residents receiving inhibitory or inducing co-medications, between men and women, or by albumin level. Total VPA clearance was similar between men and women, among age groups, or according to inducing or inhibiting co-medications.

Prevalence of Appropriate and Problematic Antiepileptic Combination Therapy in Older People in the Nursing Home

Objectives: To determine the prevalence of mono‐ and poly‐antiepileptic drug (AED) therapy in a cohort of nursing home (NH) residents and to describe specific AED combinations used, as well as demographic, clinical, and functional factors associated with poly‐AED therapy and the most common AED combination.

Population pharmacokinetics of valproic acid concentrations in elderly nursing home residents.

The objective of this study was to identify factors that affect valproic acid (VPA) apparent clearance (CL/F) in elderly nursing home residents. Inclusion criteria included residency in a nursing home for at least 2 months, aged 65 years or older, a stable dosing regimen of VPA for at least 4 weeks, VPA concentration, and complete dosing information. CL/F was analyzed by a nonlinear mixed effects model. A one-compartment model with first-order absorption and elimination was used. Both volume and absorption rate constant were fixed (14 L and 1 hr−1, respectively). Covariates were tested by forward inclusion and backward elimination. Interindividual variability in clearance was estimated using an exponential error model and expressed as a coefficient of variation. Residual error was estimated using a combined additive and constant coefficient of variation error model. The study consisted of 405 observations from 146 (52 men, 94 women) elderly nursing home residents. CL/F was not affected by age or weight. The population CL/F was 0.843 L/hr. CL/F was 1) 27% lower in female residents; 2) 41% greater when the resident was on concomitant metabolic inducers carbamazepine or phenytoin cotherapy; and 3) 25% greater when the syrup formulation was used. Variability in CL/F was 32.9%. Coefficient of variation and standard deviation of the residual error were 18.2% and 10.6 mg/L, respectively. The increased CL/F in patients taking VPA syrup may be the result of a decreased bioavailability (F) rather than an increased CL that could be associated with pathology requiring use of the syrup rather than an inherent property of the drug formulation. The results from this study may be useful for individualizing dose regimens in the nursing home population based on patient-specific factors.

Phenytoin use in elderly nursing home residents.

BACKGROUND Phenytoin (PHT) dosing regimens are often determined based on experience in those aged <65 years rather than in those aged >or=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 (6-74, 75-84, and >or=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.

Carbamazepine dose–concentration relationship in elderly nursing home residents

PURPOSE To describe the dose-concentration relationships of carbamazepine (CBZ) in elderly nursing home residents and the effect of sex, age, and type of co-medications. RESULTS This is a cross-sectional study of elderly (> or = 65 years) nursing home residents across the United States (N=92). Data collection was from 1 June 1998 to 31 December 2000. The mean CBZ dose was 9.2+/-5.4 mg/(kg day(-1)) (+/-Standard Deviation) and serum concentration was 5.9+/-2.2mg/L. The daily dose was significantly lower in the oldest-old age group (> or = 85 years, mean 476.9 mg/day (95% confidence interval CI) 326.5-627.3) as compared to the dose in the young-old (65-74 years, mean 724.4 mg/day (CI) 603.4-845.4) (p=0.016). Adjusted for body weight, doses were similar on a mg/(kg day(-1)) basis. The majority of observed CBZ serum concentrations were at the lower end (67.4%) or below (20.7%) the suggested therapeutic range for younger adult outpatients. CONCLUSIONS Total daily CBZ doses and patient weight decreased with age. The average dose for elderly nursing home residents was approximately 9 mg/(kg day(-1)). Carbamazepine serum concentrations were lower than those used for younger adults, suggesting that these patients may be more sensitive to CBZ.

The Validity of Epilepsy or Seizure Documentation in Nursing Homes

Recent studies have reported that epilepsy and seizures are common in nursing homes. Prevalence has been reported to range from 5 to 9% and antiepileptic drug (AED) use is even more common. Most of these studies have relied on various forms of nursing home records, but the validity of this source data, while assumed, has not been verified. This study evaluated the degree of agreement between the Minimum Data Set (MDS), both paper and electronic versions, and actual medical records available at the nursing home. Records of 144 residents were evaluated; agreement between paper and electronic versions of the MDS was 97.8%. Agreement between the paper version of the MDS and neurologists review of the nursing home record was 92.3%. However, the criteria for diagnosing epilepsy or seizure were not well documented. Nevertheless, the agreement among nursing home records, paper MDS and electronic MDS is great enough to allow the electronic MDS to be used as a research tool, but more investigation of the actual criteria used by nursing home physicians in diagnosing epilepsy and seizures is necessary.