ArticleClinical pharmacokinetics2015
Paraxanthine/Caffeine Concentration Ratios in Hair: An Alternative for Plasma-Based Phenotyping of Cytochrome P450 1A2?
Article in Clinical pharmacokinetics, 2015. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.
What it found
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Who cites it
2 citing papers in PubMed, 9 citations in OpenAlex.
- Determination of Urinary Caffeine Metabolites as Biomarkers for Drug Metabolic Enzyme Activities.Nutrients · 2019Article
- Alternative Sampling Strategies for Cytochrome P450 Phenotyping.Clinical pharmacokinetics · 2016Review
Corrections and comments
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Authors and funding
3 authors at 2 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
BACKGROUND AND
objectiveAlthough metabolite-to-parent drug concentration ratios in hair have been suggested as a possible tool to study the metabolism of drugs in a non-invasive way, no studies are available that evaluated this in a systematic way. Cytochrome P450 (CYP) 1A2 is a drug-metabolizing enzyme characterized by large inter-individual differences in its activity. The standard approach for CYP1A2 phenotyping is to determine the paraxanthine/caffeine ratio in plasma at a fixed timepoint after intake of a dose of the CYP1A2 substrate caffeine. The aim of this study was to evaluate whether paraxanthine/caffeine ratios measured in hair samples reflect the plasma-based CYP1A2 phenotype.
methodsCaffeine and paraxanthine concentrations were measured in proximal 3 cm segments of hair samples from 60 healthy volunteers and resulting paraxanthine/caffeine ratios were correlated with CYP1A2 phenotyping indices in plasma.
resultsParaxanthine/caffeine ratios in hair ranged from 0.12 to 0.93 (median 0.41); corresponding ratios in plasma ranged from 0.09 to 0.95 (median 0.40). A statistically significant correlation was found between ratios in hair and plasma (r = 0.41, p = 0.0011). However, large deviations between ratios in both matrices were found in individual cases. Although the influence of several factors on paraxanthine/caffeine ratios and hair-plasma deviations was investigated, no evident factors explaining the observed variability could be identified.
conclusionThe variability between hair and plasma ratios complicates the interpretation of hair paraxanthine/caffeine ratios on an individual basis and, therefore, compromises their practical usefulness as alternative CYP1A2 phenotyping matrix.
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