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The effect of malignant effusions on methotrexate disposition
1Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha 68198-6025, USA.
Cancer Chemotherapy and Pharmacology
|November 20, 2002
Summary
Malignant effusions can alter methotrexate pharmacokinetics, increasing its half-life and potential toxicity. This study used a PBPK model to simulate these effects, highlighting the importance of effusion characteristics.
Area of Science:
- Pharmacokinetics
- Oncology
- Medical Modeling
Background:
- Malignant effusions are common in cancer patients.
- Drug pharmacokinetics can be altered by fluid accumulation.
- Methotrexate (MTX) is a widely used chemotherapy agent.
Purpose of the Study:
- To evaluate how malignant effusions impact the pharmacokinetics of methotrexate (MTX).
Main Methods:
- A physiologically based pharmacokinetic (PBPK) model for MTX was adapted to include effusion spaces.
- Simulations assessed MTX concentrations in plasma and effusion fluid under various effusion conditions.
- Model predictions were validated against clinical data from a patient with pleural effusion.
Main Results:
- The PBPK model accurately predicted MTX plasma concentrations in patients with and without effusions.
- Effusion characteristics (volume, protein binding, permeability) significantly influence MTX pharmacokinetics.
- Malignant effusions create a 'third space,' increasing MTX's volume of distribution and terminal half-life, potentially leading to toxicity.
Conclusions:
- Malignant effusions significantly alter MTX disposition, increasing its half-life.
- This pharmacokinetic change may lead to unexpected MTX toxicity in cancer patients.
- PBPK modeling is a valuable tool for predicting drug behavior in the presence of effusions.