Related Experiment Video

Updated: Aug 9, 2026

Mass Spectrometry and Luminogenic-based Approaches to Characterize Phase I Metabolic Competency of In Vitro Cell Cultures
10:44

Mass Spectrometry and Luminogenic-based Approaches to Characterize Phase I Metabolic Competency of In Vitro Cell Cultures

Published on: March 28, 2017

Prediction of maximum exposure in poor metabolizers following inhibition of nonpolymorphic pathways

C Collins1, R Levy, I Ragueneau-Majlessi

  • 1Department of Pharmaceutics, University of Washington, Seattle, 98195, USA. carolc3@u.washington.edu

Current Drug Metabolism
|April 14, 2006
PubMed

Insights

Drug exposure can significantly increase in individuals with poor drug metabolism when taking certain inhibitors. A new predictive model helps identify high-risk substrates, improving drug safety during clinical trials.

Area of Science:

  • Pharmacokinetics
  • Drug Metabolism
  • Clinical Pharmacology

Background:

  • Inhibitors of nonpolymorphic enzymes can cause substantial increases in drug exposure in poor metabolizers.
  • Clinical trials show variable increases in drug exposure ratios, raising safety and ethical concerns.

Purpose of the Study:

  • To develop a predictive model for maximum drug exposure in poor metabolizers when co-administered with inhibitors.
  • To identify drug substrates susceptible to large increases in exposure.

Main Methods:

  • Literature data mining to identify relevant clinical trials.
  • Development of a theoretical approach to predict maximum exposure in poor metabolizers.
  • Validation of the predictive model using existing clinical trial data.

Main Results:

  • The predictive model achieved a mean percentage difference of 11.9% between predicted and observed maximum exposure.
  • Substrates with a high fraction metabolized by polymorphic enzymes (fm(POLY) > 75%) are at increased risk for > tenfold exposure increases.

Conclusions:

  • A theoretical model can effectively predict drug exposure in poor metabolizers.
  • Identifying substrates with high fm(POLY) is crucial for assessing risks associated with enzyme inhibitors.

Related Concept Videos

Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase01:27

Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase

Phase II biotransformation reactions are essential for detoxifying and eliminating xenobiotics, including many pharmaceutical compounds. These reactions typically involve conjugation, the covalent attachment of polar endogenous groups such as glucuronic acid, sulfate, methyl, or acetyl moieties to functional groups introduced during Phase I metabolism. The resulting conjugates are more water-soluble, enabling efficient renal or biliary excretion.The major classes of Phase II enzymes include...
Pharmacogenetics of Drug Metabolism: Overview01:27

Pharmacogenetics of Drug Metabolism: Overview

Genetic polymorphism in drug metabolism is crucial to the inter-individual variability observed in drug responses. Drug metabolism primarily involves the chemical modification of drugs and other xenobiotics to enhance their elimination by increasing their polarity. Two main classes of enzymes mediate this biotransformation process: Phase I enzymes, primarily cytochrome P450s, catalyze oxidation and reduction reactions, while other enzymes, such as esterases, mediate hydrolysis, and Phase II...
Pharmacogenetics of Phase I Enzymes: Cytochrome P450 Isozymes01:28

Pharmacogenetics of Phase I Enzymes: Cytochrome P450 Isozymes

Cytochrome P450 (CYP450) enzymes are a superfamily of heme-containing monooxygenases that play a pivotal role in Phase I drug metabolism by catalyzing oxidation and reduction reactions.These enzymes transform lipophilic xenobiotics into more hydrophilic metabolites, facilitating subsequent Phase II conjugation and eventual excretion. The CYP450 family is classified into families (e.g., CYP1–CYP3) and subfamilies (e.g., CYP2A, CYP2C), based on amino acid sequence homology.CYP450 isoenzymes,...
Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu01:29

Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu

Genetic variations significantly influence drug response through pharmacokinetics, receptor interactions, and biologic milieu modifications. Pharmacokinetic alterations impact drug metabolism and clearance, affecting efficacy and toxicity. Variants in drug-metabolizing enzymes, such as CYP2C9 and CYP2C19, alter drug activation and elimination. For example, CYP2C9 loss-of-function variants require lower warfarin doses to prevent excessive bleeding, while CYP2C19 variants reduce clopidogrel...
Nonlinear Pharmacokinetics: Dependence of Elimination Half-Life and Dose Clearance01:23

Nonlinear Pharmacokinetics: Dependence of Elimination Half-Life and Dose Clearance

The elimination half-life and drug clearance of drugs following nonlinear kinetics can vary with dosage. The Michaelis-Menten parameters and drug concentration influence these factors. As the dose increases, the elimination half-life tends to lengthen, resulting in a reduction in clearance and a disproportionately larger area under the curve. The total clearance can be derived from the Michaelis-Menten equation for drugs following a one-compartment model.
A study on guinea pigs examined the...
Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase01:11

Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase

Genetic polymorphisms in drug targets have emerged as critical determinants of interindividual variability in drug response and toxicity. Pharmacogenomic investigations increasingly focus on identifying these variations to personalize and optimize therapeutic interventions. A drug target may be a receptor, enzyme, or signaling protein involved in pharmacologic responses or disease-related pathways. While early pharmacogenetic studies focused primarily on drug metabolism, current research...