We all have some medicine in a drawer that’s been lying around for months (or years). If it expires, you should throw it away. The expiration date is not just a suggestion, you really shouldn’t be taking expired drugs. In space, that advice is even more critical.

We don’t really know how medicines react to space. The microgravity and radiation aboard long-range space missions may change their effectiveness and potency — and they may not last as long, either.

That’s all the more reason to be aware of expiration dates.

“It doesn’t necessarily mean the medicines won’t work, but in the same way you shouldn’t take expired medications you have lying around at home, space exploration agencies will need to plan on expired medications being less effective,” said senior study author Daniel Buckland, M.D., Ph.D., an assistant professor of emergency medicine at Duke University School of Medicine and an aerospace medicine researcher.

Medication won’t make it to Mars

Buckland used a database of international drug expiration dates and found that more than half of the medicine that may be taken on a long-term space mission (54 out of 91 verified) have an expiration date of 36 months or less. So, even in the most optimistic Mars mission scenario, these drugs would expire. In scenarios where the Mars mission lasts even longer, almost every drug considered would expire — and this is assuming that drugs will last as long in space as on Earth.

“Prior experience and research show astronauts do get ill on the International Space Station, but there is real-time communication with the ground and a well-stocked pharmacy that is regularly resupplied, which prevents small injuries or minor illnesses from turning into issues that affect the mission,” Buckland said.

But on Mars, this will likely not be an option. This means that any missions must consider these issues in advance and prepare for them accordingly, possibly even by tweaking the medicine recipe, or at the very least, by selecting longer-lasting drugs.

“Those responsible for the health of space flight crews will have to find ways to extend the expiration of medications to complete a Mars mission duration of three years, select medications with longer shelf-lives, or accept the elevated risk associated with administering expired medication,” Diaz said.

Astronauts venturing on long-term missions will need reliable access to medications that maintain their efficacy, despite the unique challenges posed by space. This is not just about treating minor ailments; it’s about safeguarding the health of those pushing the boundaries of human exploration.

Human health in space

This is just one of the many health problems that astronauts will have to face on longer missions.

Astronauts on long-term space missions can face a range of health problems due to the unique conditions of space. These include muscle atrophy and bone density loss from prolonged weightlessness, vision impairment caused by fluid shifts, and a weakened immune system. Additionally, the high levels of cosmic radiation increase the risk of cancer and cardiovascular diseases. Mental health issues can also arise from isolation, confinement, and the stress of space travel.

Furthermore, without immediate access to medical facilities, even minor injuries or illnesses could become serious. Addressing these challenges is essential for the success of extended missions beyond Earth’s orbit. For now, this study highlights that we need to take a closer look at the medicines that astronauts would undoubtedly need for these long-term missions and figure out ways to ensure that they’ll work as prescribed.

Journal Reference: Thomas E. Diaz, Emma C. Ives, Diana I. Lazare, Daniel M. Buckland. Expiration analysis of the International Space Station formulary for exploration mission planning. npj Microgravity, 2024; 10 (1) DOI: 10.1038/s41526-024-00414-3