Free radicals in irradiated drugs: an EPR study
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Updated: Oct 19, 2026

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
F A Taiwo1, L H Patterson, E Jaroszkiewicz
1School of Pharmacy and Pharmaceutical Sciences, De Montfort University, The Gateway, Leicester, UK. ttaiwo@dmu.ac.uk
Abstract:
Exposure of dry powder forms of the drugs nitrendipine, nifedipine, felodipine, and nimodipine to gamma-radiation results in the formation of free radicals detected by electron paramagnetic resonance (EPR) spectroscopy. The four structurally related drugs show qualitatively identical EPR spectral features in terms of g-values, the qualitative descriptive parameter. These radicals are very stable, surviving long periods of time in excess of 9 months and possibly beyond conventional shelf-life of the drugs. The residual radical population is high enough to be detectable after long storage. Administration of such radiation-treated drugs may present patients with quantities of free radicals and possibilities of secondary cell damage.
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