One of the concerns for space explorations of greater distances is that the medicines for the astronauts would not last long enough. Unlike the ISS, whose medical supplies are regularly replenished, space explorations would isolate astronauts for longer periods of time.

Researchers from the Center for Space Medicine at the Baylor College of Medicine investigated the degradation of nine types of medicines that stayed aboard the ISS and are taken back to Earth after 550 days. These medicines, which included painkillers, antidiarrheal drugs, sleeping pills, antihistamines and alertness drugs, were kept for three to five months on Earth under controlled conditions before they were studied.

Using guidelines from the United States Pharmacopeia (USP), the researchers determined if the medicines were still viable after staying in space for about one and a half years. They found out that of the 11 drugs, only one was no longer viable - 11 months after its expiry, it did not meet USP standards. On the contrary, four of the medicines remained viable up to eight months after their expiry, and one was viable five months after its expiry. Three drugs met USP standards three months before their expiry, according to a press release.

The researchers noted that there were no unusual degradation products in the medicine samples.

"Limited, evidence-based extension of medication shelf-lives may be possible and would be useful in preparation for lengthy exploration missions," the researchers concluded, adding that "analysis of flight-aged samples compared to appropriately matched ground controls will permit determination of the spaceflight environment on medication stability."

The study was published in the online Nov. 6 issue of The AAPS Journal.