NASA scientists have been wondering how the different conditions in outer space would affect medicines packed by astronauts from Earth for a long time now, hoping to identify any medications that may degrade quickly once they leave the Earth’s atmosphere. According to a report from UPI, a recent study shows that the majority of drugs do not degrade at a significantly faster rate in space than they do on Earth.

Researchers have concluded a 550-day study of a number of drugs on the International Space Station. The medicines tested included sleeping aids, painkillers, antihistamines, antidiarrheal drugs, and an alertness drug. None of the medications aboard the space station during the study period showed signs of accelerated degradation.

This doesn’t mean that drugs in space will last forever, however. Drug degradation is influenced by a number of environmental factors, including exposure to light and oxygen.

According to researchers at the Baylor College of Medicine in Texas, and the Center for Space Medicine and Department of Pharmacology, higher levels of radiation and the altered gravity aboard the International Space Station had no adverse effects on the drugs stored there.

The medications aboard the space station had all passed their expiration date, but tests at Baylor showed that four out of nine still met viability standards after months of being aboard the ISS. The study’s findings were published this week in the AAPS Journal.

The scientists are pleased with their preliminary results, but say that more time is necessary to determine which drugs will be viable to bring along on long expeditions into deep space. They will need to conduct more studies to be able to say for sure which medications hold up the best.

A press release outlining the details of the study can be found here.