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The aqueous stability of bupropion
Paul M O'Byrne1, Robert Williams, John J Walsh
1School of Pharmacy and Pharmaceutical Sciences, Trinity College, Dublin 2, Ireland. obyrnep@tcd.ie
Journal of Pharmaceutical and Biomedical Analysis
|June 16, 2010
Summary
Bupropion is most stable in aqueous solutions below pH 5. Its degradation is primarily catalyzed by hydroxide ions, impacting its therapeutic use, formulation, and storage.
Area of Science:
- Pharmaceutical Chemistry
- Physical Chemistry
- Analytical Chemistry
Background:
- Bupropion is a widely used antidepressant medication.
- Understanding its aqueous stability is crucial for effective therapeutic application and formulation development.
Purpose of the Study:
- To determine the aqueous stability of bupropion.
- To elucidate the pH-degradation profile and kinetics.
- To identify degradation products and propose a degradation mechanism.
Main Methods:
- High-performance liquid chromatography with UV detection (HPLC-UV).
- Liquid chromatography-mass spectrometry (LC-MS).
- Non-linear regression analysis for pH-degradation profile determination.
Main Results:
- Bupropion degradation follows first-order reaction kinetics in aqueous solutions.
- The drug is most stable at pH values below 5.
- Degradation is catalyzed by water and significantly by hydroxide ions acting on the unionized form.
- Activation energy and frequency factor for decomposition at pH 10.7 were determined.
Conclusions:
- The inherent instability of bupropion above pH 5 has significant implications for its therapeutic use, formulation, pharmacokinetics, and analytical procedures.
- Knowledge of degradation pathways is essential for optimizing bupropion's clinical application and shelf-life.
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