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Gamma Irradiation of Ready-to-Use Injectable Aqueous Suspensions: Impact on Particle Size, Rheology, Interfacial
Swetha Ainampudi1, Matthew Zajac2, Sushesh Srivasta Palakurthi3
1GlaxoSmithKline, 1250 South Collegeville Rd, Collegeville, Pennsylvania 19426-2990, USA Swetha.x.ainampudi@gsk.com Ainampudi.swetha@gmail.com.
PDA Journal of Pharmaceutical Science and Technology
|April 29, 2026
Summary
Gamma sterilization of ready-to-use injectable suspensions is viable, but polymer degradation impacts long-term physical stability. Formulation adjustments are crucial to mitigate radiolytic effects and ensure shelf life.
Area of Science:
- Pharmaceutical Sciences
- Materials Science
- Radiochemistry
Background:
- Ready-to-use (RTU) injectable aqueous suspensions require terminal sterilization for sterility assurance.
- Aseptic processing is common but offers less sterility assurance than terminal sterilization.
- Gamma sterilization presents a potential terminal sterilization method for RTU suspensions.
Purpose of the Study:
- To investigate the impact of gamma sterilization on model RTU aqueous suspensions.
- To evaluate physicochemical changes in suspensions with varying polymer types and drug loads.
- To assess the viability of gamma sterilization as a terminal sterilization method.
Main Methods:
- Model RTU aqueous suspensions with different polymers and drug loads were prepared.
- Comprehensive physicochemical characterization was performed.
- Gamma irradiation was applied, followed by analysis using size exclusion chromatography (SEC) and HPLC.
Main Results:
- Gamma irradiation stabilized particle size and did not affect drug solid-state form.
- Significant radiolytic degradation of polymeric surfactants (poloxamer 338, PEG 3350) was observed.
- Degradation reduced viscosity and injection force but compromised long-term physical stability, causing caking.
Conclusions:
- Gamma irradiation is a plausible terminal sterilization method for RTU injectable suspensions.
- Radiolytic polymer degradation necessitates formulation design considerations.
- Maintaining long-term physical stability requires strategies to counteract polymer degradation effects.
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