Limited Degradation of Active Pharmaceutical Ingredient After Spaceflight on the International Space Station.

IntroductionSpaceflight may accelerate degradation of active pharmaceutical ingredients, raising concerns about medication stability during long-duration missions. This study assessed the potency of active pharmaceutical ingredients in a convenience sample of medications flown to the International Space Station alongside lot-matched terrestrial control samples.MethodsSpaceflight-exposed samples and terrestrial control samples were analyzed using ultra-high-performance liquid chromatography with tandem mass spectrometry. At the time of analysis, all medications were beyond their labeled expiration dates following prolonged storage and delayed laboratory testing. Medications included caffeine, diazepam, diphenhydramine, epinephrine, ketamine, lidocaine, naloxone, and promethazine in solid and liquid formulations. Percent difference between exposed and control samples was calculated, and absolute potency was evaluated relative to 95 to 105% and 80 to 120% ranges. Regression analyses examined associations of changes in the potency of active pharmaceutical ingredients with days in space and days expired.ResultsMost samples from both groups fell outside the 95 to 105% range. However, >90% remained within the broader 80 to 120% range. Average percent differences between spaceflight-exposed and ground control samples were generally within ±5% for most medications, suggesting limited relative potency differences despite prolonged spaceflight exposure. Epinephrine exhibited the most consistent reductions, averaging 10% lower potency than control samples. Regression analyses identified medication-specific associations with days expired and days in space but did not show a consistent pattern of spaceflight-associated potency loss.ConclusionWithin the limitations of this lot-matched, post-storage comparison, International Space Station exposure was not associated with large relative potency changes for most medications studied. Epinephrine represented the clearest exception and may require medication-specific stabilization strategies for long-duration space exploration missions.