Clinical Chemistry AACC Online Job Center
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Clinical Chemistry 46: 1132-1135, 2000;
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Submit an electronic Letter to
the Editor about this paper
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (21)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Burt, M.
Right arrow Articles by Apple, F. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Burt, M.
Right arrow Articles by Apple, F. S.
Related Collections
Right arrow Laboratory Management
Right arrow Evidence Based Laboratory Medicine and Test Utilization
Right arrow Drug Monitoring and Toxicology
(Clinical Chemistry. 2000;46:1132-1135.)
© 2000 American Association for Clinical Chemistry, Inc.

Articles

Evidence-based Implementation of Free Phenytoin Therapeutic Drug Monitoring

Martha Burt1, David C. Anderson1, Julie Kloss1 and Fred S. Applea,1

1 Departments of Laboratory Medicine and Pathology and Neurology, Hennepin County Medical Center, University of Minnesota School of Medicine, Minneapolis, MN 55415.
a Address correspondence to this author at: Hennepin County Medical Center, Clinical Laboratories 812, 701 Park Ave., Minneapolis, MN 55415. Fax 612-904-4229; e-mail fred.apple{at}co.hennepin.mn.us

Background: The majority of laboratories measure total phenytoin concentration for therapeutic drug monitoring. However, there are substantial interindividual variations in free phenytoin concentrations, the pharmacologically active component.

Methods: We describe the process and data used to implement monitoring of free phenytoin only in an urban medical center. Over a 6-week period, total and free phenytoin concentrations were measured, clinical charts reviewed, and indications for alterations in the percentage of free phenytoin fraction were determined.

Results: Of the 189 phenytoin requests from 139 patients, 136 data points were analyzed. Free phenytoin concentrations were 6.8–35.3%, with 50% outside the expected range of 8–12%. Clinical indications likely responsible for variations were hypoalbuminemia, drug interactions, uremia, pregnancy, and age. Overall, 30% of patients demonstrated a discrepancy between therapeutic, subtherapeutic, or supratherapeutic concentrations between free and total phenytoin concentrations. The largest discordance (53%) occurred in the patient group with free phenytoin <8% or >12%.

Conclusions: This study supports previous clinical findings that monitoring total phenytoin is not as reliable as free phenytoin as a clinical indicator for therapeutic and nontherapeutic concentrations. Thus, we recommend that therapeutic monitoring should use free phenytoin concentrations only.




The following articles in journals at HighWire Press have cited this article:


Home page
 Clin. Chem.Home page
R. De Smet, J. Van Kaer, B. Van Vlem, A. De Cubber, P. Brunet, N. Lameire, and R. Vanholder
Toxicity of Free p-Cresol: A Prospective and Cross-Sectional Analysis
Clin. Chem., March 1, 2003; 49(3): 470 - 478.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2000 by the American Association for Clinical Chemistry.