Related Experiment Video
Updated: Jun 16, 2026

Multi-Gene Single Nucleotide Polymorphism Detection in Gastric Cancer Based on Ion Semiconductor Sequencing Platform
Published on: May 10, 2024
Do 5-fluorouracil therapies alter CYP2C19 metaboliser status?
N A Helsby1, W Y Lo, P Thompson
1Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand. n.helsby@auckland.ac.nz
5-fluorouracil (FU) treatment altered a patient's CYP2C19 metaboliser status, leading to decreased enzyme activity and a shift from extensive to poor metaboliser. This change coincided with the development of hand and foot syndrome.
Area of Science:
- Pharmacogenomics
- Drug Metabolism
- Oncology
Background:
- Colorectal cancer treatment often involves 5-fluorouracil (FU/FA).
- Individual variability in drug metabolism influences treatment efficacy and toxicity.
- Cytochrome P450 enzymes, including CYP2C19, play a crucial role in drug metabolism.
Observation:
- A patient with colorectal adenocarcinoma received 5-fluorouracil and folinic acid (FU/FA).
- CYP2C19 genotype and activity were assessed using proguanil as a probe substrate.
- The patient's CYP2C19 activity decreased significantly during FU/FA treatment, altering their metaboliser status.
Findings:
- The patient, initially an extensive CYP2C19 metaboliser (CYP2C19*1/*1), became a poor metaboliser during FU/FA therapy.
- This metabolic shift occurred between day 7 and day 21 of testing.
- Grade III hand and foot syndrome developed during the period of reduced CYP2C19 activity.
Implications:
- 5-fluorouracil (FU) may inhibit CYP2C19 synthesis, impacting drug metabolism.
- Altered CYP2C19 activity could influence the clinical outcomes of drugs metabolized by this enzyme, such as warfarin and phenytoin.
- This case highlights the potential for chemotherapy to affect pharmacogenetic profiles and drug disposition.
Related Concept Videos
Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase
Pharmacogenetics of Phase I Enzymes: Cytochrome P450 Isozymes
Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase
Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu
Pharmacogenetics of Drug Metabolism: Overview
Effect of Hepatic Disease on Pharmacokinetics: Drug Dosing and Hepatic Blood Flow
