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Published on: March 28, 2017
Rapid screening for polymorphisms in dextromethorphan and mephenytoin metabolism
R J Guttendorf1, M Britto, R A Blouin
1College of Pharmacy, University of Kentucky, Lexington 40536.
Coadministration of dextromethorphan and mephenytoin did not significantly alter their metabolic ratios in healthy volunteers. This study identified poor metabolizers for both drugs, aiding in understanding drug metabolism variations.
Area of Science:
- Pharmacology
- Drug Metabolism
- Clinical Pharmacology
Background:
- Dextromethorphan and mephenytoin are commonly used probe drugs to assess cytochrome P450 enzyme activity.
- Understanding inter-individual variability in drug metabolism is crucial for personalized medicine.
- Simultaneous administration of probe drugs can potentially affect their individual metabolic profiles.
Purpose of the Study:
- To evaluate the impact of coadministering dextromethorphan and mephenytoin on their respective metabolic phenotypes.
- To screen a population for poor metabolizer phenotypes of mephenytoin 4-hydroxylase and dextromethorphan O-demethylase.
Main Methods:
- A randomized 3-way crossover study design was employed in 48 healthy male volunteers.
- Phenotyping parameters, including urinary S-/R-mephenytoin ratio and dextromethorphan metabolic ratio, were assessed.
- Subjects were screened for poor metabolizer (PM) status for both drugs using non-quantitative methods, with dextromethorphan PMs confirmed by metabolic ratio evaluation.
Main Results:
- Coadministration of dextromethorphan and mephenytoin did not significantly alter the urinary S-/R-mephenytoin ratio or the dextromethorphan metabolic ratio.
- Out of 519 screened subjects, 3.7% were identified as poor metabolizers (PMs) of mephenytoin, and 6.7% as PMs of dextromethorphan.
- All identified dextromethorphan PMs were confirmed through rigorous metabolic ratio assessment.
Conclusions:
- Simultaneous administration of dextromethorphan and mephenytoin is a valid method for phenotyping drug metabolism without mutual interference.
- The study successfully identified individuals with poor metabolizer phenotypes for these key drug-metabolizing enzymes.
- These findings support the use of combined probe drugs for efficient screening of metabolic phenotypes in clinical settings.
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