1. Design: Retrospective electronic chart review
• Approved by the Glenwood Resource Research and Development
Committee
Population: Intellectually disable adults
Inclusion Criteria:
• Individuals on phenytoin for seizure indication
• Individual’s phenytoin dose was the same before and after
interchange
Exclusion Criteria:
• Hospitalization or documented prolonged acute illness (e.g.
pneumonia)
• Only available levels within 2 weeks of interchange
• Drug regimen changes including new medications with potential
drug interactions with phenytoin
• Dose change
Statistical Analysis
• Paired t-test was done to determine if there is a difference
between before and after interchange levels
• Power analysis was not done due to the nature of study having a
limited number of individuals in the population
Determine if individuals that switched from brand-name to generic
phenytoin had decreased serum concentration levels and change in
seizure frequency in an intermediate care facility for intellectually
disabled.
• Phenytoin is an antiepileptic drug used to treat generalized and
partial seizures.
• The FDA indicates that generic formulations of phenytoin have an
AB-rating to brand-name formulations.
• Studies that found the switch to be favorable conclude that brand
phenytoin is not superior to generic phenytoin (Gagne, 2015;
Kinikar, 2012; Kesselheim, 2010; Yamada, 2011).
• Some studies suggest some patients may be prone to complications
that have been reported with interchange (Yamada, 2011).
Safety of interchange between brand-name to generic phenytoin
David Quach1
; Sheila Glencer, PharmD2
; Ashley Wolfson-McClure, PharmD2
1. University of Iowa College of Pharmacy, 2. Glenwood Resource Center, Iowa Department of Health Services
OBJECTIVE
DISCLOSURE
• The views expressed in this poster are those of the authors and do
not necessarily reflect the position or policy of the Iowa Department
of Human Services.
• This material is the result of work supported with resources and the
use of facilities at the Glenwood Resource Center.
SECONDARY OUTCOMES
METHODS
BACKGROUND
PRIMARY OUTCOME
BASELINE CHARACTERISTICS
n = 12
Age (years), mean (SD) 53.4 (11.2)
Sex, n (%) Male
Female
8 (66.7)
4 (33.3)
Seizure Type, n (%) Partial
Generalized
Unspecified
2 (16.7)
8 (66.6)
2 (16.7)
Total daily dose (mg), mean 293.75 (45.4)
Duration of prior phenytoin in
years, mean
>5 years
Total AEDs, mean (SD) 2.25 (1.13)
Documented seizure 6 months prior
to interchange, n (%)
Yes
No
2 (16.7)
10 (83.3)
CONCLUSIONS
• The phenytoin levels before and after interchange were not
significantly different (-0.785mg/L; 95% CI, -0.855mg/L to
2.425mg/L, p=0.197). This result may show the safety for
interchange. Further, lack of change in seizure frequency during
interchange suggest that interchange is safe.
• There was no association was found between increased total
number of antiepileptic medications and phenytoin level changes
>1mg/L vs. <1mg/L (2.83 vs. 1.67 AEDs, p=0.110).
• The information collected after interchange in this study is relatively
short for time period of collection compared to information
collected before the interchange. The clinical significance for safety
of the interchange must be assessed further with larger, and long-
term studies.