When aerospace engineers design the new vehicle intended for long-duration space travel, they will need to include a good-sized medicine cabinet. Stocking it, however, is more of a challenge than a quick run to the pharmacy, according to results published from the Stability of Pharmacotherapeutic and Nutritional Compounds, or Stability, investigation.

This study, which explored pharmaceutical stability on the International Space Station, shows that many medications deteriorate faster in space.

Data from past shuttle missions prompted the investigation, after researchers found certain medications packed aboard the orbiter degraded more rapidly than on Earth. To pinpoint the cause of deterioration, the study had to look at everything from packaging to physical and chemical characteristics of specific medicines.

Principal Investigator Lakshmi Putcha, Ph.D., comments on the multitude of conditions specific to space missions that may be responsible for product breakdown.

"Unique environmental factors include, but are not limited to, ambient radiation, excessive vibrational forces, multiple gravity environments and carbon dioxide enrichment; this is in addition to unconventional packaging, resupply operations and other unknowns," said Putcha.

The U.S. Food and Drug Administration, or FDA, regulates the safety of medications for human consumption. The Stability study showed, however, that FDA standards may be compromised for medications during space travel. "If pharmaceuticals degrade into chemicals that we do not know the concentration and chemical characteristics to set toxicity limits for," commented Putcha, "then medications could become not only less effective, but even dangerous."

Researchers studied 35 different medications, including solids, liquids, and capsules. The variety of the selected pharmaceuticals reflected the potential needs for crew members to address everything from headaches to fevers. Putcha emphasizes the varied medical concerns long-duration spaceflight may encounter.

"In the future we will need to pack long-acting antibiotics, as well as bone, muscle, and immune function enhancing drugs. This is in addition to radiation protectants, cardiovascular medications, anti-anxiety and anti-depressants, fatigue reducing and performance enhancing medications, and drugs for emergency medicine, to list some of the ones needed for the space station and beyond," said Putcha.

The medicines, which were contained in identical stability kits, launched to the space station aboard STS-121 in July 2006 and remained in orbit for different durations. The first kit returned with the landing of the STS-121 mission, followed by the second, third and fourth kits in June 2007, Feb. 2008 and Nov. 2008, respectively.

The samples that were exposed to the space environment were examined after return to Earth for physical and chemical characteristics to check their level of degradation against ground-based control samples.

A higher percentage of medications from each flight kit degraded, compared to those in ground control kits. Of the antibiotic medications studied, Augmentin was the most unstable due to one of its ingredients: clavulanate. The degradation of clavulanate in space caused the drug to lose almost 50% potency.

This was much sooner than the manufacturer's expiration date on the label. Comparatively, the investigation showed that the antibiotic imipenem/cilastatin - flown in original commercial packaging - remained relatively stable in flight and on the ground.

Part of the challenge with medications in space involves packaging. Due to stowage requirements, some products are taken out of their original manufacturer's container and repacked for flight. This can increase the susceptibility of the drug to the spacecraft's ambient environmental conditions and decrease the anticipated shelf life.

Results show that 18 of the 33 medications, even from ground control kits, were unstable before projected expiration dates, most likely due to repackaging.

Currently aboard the space station, medications are replaced six months prior to their labeled expiration date. For long-duration space exploration, however, such frequent resupply is not possible. Researchers recommend development of more stable formulations and robust packaging based on the results of this study.

The investigation also helped to identify some medications that are stable and maintained their shelf-life in space. Selecting pharmaceuticals with sustained stability implies potential cost savings and more reliable products for crew consumption.

Here on Earth, the results of the Stability investigation can advance the knowledge of environmental effects on food and drugs for remote site medicine and inhabitants of extreme locations, like the Antarctic.

The data can also contribute to the development of mathematical models to predict medication shelf life in adverse environments, such as low Earth orbit and beyond. In addition, this research could aid in development of improved packaging and shielding materials, as well as more stable pharmaceutical formulations.