Study of volatile compounds from the radiosterilization of solid cephalosporins

Limitations in predicting radiation-induced pharmaceutical instability during long-duration spaceflight

As human spaceflight seeks to expand beyond low-Earth orbit, NASA and its international partners face numerous challenges related to ensuring the safety of their astronauts, including the need to provide a safe and effective pharmacy for long-duration spaceflight. Historical missions have relied upon frequent resupply of onboard pharmaceuticals; as a result, there has been little study into the effects of long-term exposure of pharmaceuticals to the space environment. Of particular concern are the long-term effects of space radiation on drug stability, especially as missions venture away from the protective proximity of the Earth. Here we highlight the risk of space radiation to pharmaceuticals during exploration spaceflight, identifying the limitations of current understanding. We further seek to identify ways in which these limitations could be addressed through dedicated research efforts aimed toward the rapid development of an effective pharmacy for future spaceflight endeavors.

Chemical analysis of solid-state irradiated human insulin

PURPOSE

To study the chemical modifications induced upon irradiation of solid human insulin at radiosterilization doses and investigate the influence of the absorbed dose on radiolysis.

MATERIALS AND METHODS

Volatile radiolytic products were monitored by gas chromatography coupled with mass spectrometry (GC-MS) and non-volatile products by two different high performance liquid chromatography (HPLC) methods: the formation of higher molecular weight proteins was assessed by size exclusion liquid chromatography whereas assays for related compounds and chemical potency tests were carried out using reverse-phase HPLC-UV. Conformational changes were investigated by measurements of circular dichroism.

RESULTS

After gamma irradiation at 10 kGy, the recovery of insulin was 96.8%; higher molecular weight proteins accounted for 0.35% (relative peak area) and other related compounds (including A21 desamido insulin) represented 1.29%. No major structural changes and no volatile radiolytic compounds were detected.

CONCLUSION

Human insulin samples irradiated in the solid-state at 10 kGy (gamma rays) and 14 kGy (electron-beam) meet the European Pharmacopoeia requirements and can be considered as quite stable towards radiation from a chemical analysis viewpoint.

Electron Beam and Gamma Radiolysis of Solid-State Metoclopramide

PURPOSE

Study the radiolysis of solid-state metoclopramide hydrochloride at various absorbed doses. Elucidate the structure of the degradation products to gain information on the radiolysis mechanisms.

METHODS

Solid-state metoclopramide samples were irradiated at several doses with gamma rays and high-energy electrons to evaluate the influence of the dose rate. High-performance liquid chromatography with a diode array detector was used to measure the chemical potency as a function of the absorbed dose and to quantify the degradation products. The characterization of degradation products was performed by liquid chromatography/atmospheric pressure chemical ionization/tandem mass spectrometry.

RESULTS

The degradation of solid-state metoclopramide after irradiation was negligible. No qualitative or quantitative differences were observed between gamma and electron beam irradiations (no dose rate effect). Four degradation products that were similar to metoclopramide were detected in trace levels (below 0.1% of the drug concentration) and were not unique to irradiation because they were found in lower amounts in unirradiated metoclopramide. The major degradation product formed after radiation was due to the loss of the chlorine atom from the metoclopramide molecule.

CONCLUSION

Solid-state metoclopramide is radioresistant from a chemical point of view and therefore could be a suitable candidate for radiosterilization studies by either gamma rays or high-energy electrons.

Radiosterilization of cefotaxime: investigation of potential degradation compounds by liquid chromatography-electrospray mass spectrometry

The nonvolatile radiolytic compounds produced by irradiation of cefotaxime were studied by a liquid chromatography-electrospray mass spectrometry method. Full scan LC-MS was first performed in order to obtain the m/z value of the protonated molecules of all detected peaks. LC-MS-MS was then carried out on the compounds of interest. A comparison between the MS-MS spectrum of cefotaxime and those of the radiolytic compounds showed that their fragmentation patterns were very similar suggesting that they were structural analogues of the main drug. The examination of the two main fragmentation pathways also permitted the location of the modified substructures. Moreover, it was shown that some stereoisomers appeared with the irradiation process. The complete fragmentation pattern of cefotaxime was studied by MSn and used to obtain information about the structure of the radiolytic compounds. A complete structure was proposed for four of these.