Medicines do not expire faster in space. The degradation in space does not differ from what is usually seen on Earth. Scientists have recently tested a number of drugs that are returned to Earth after 550 days of storage in International Space Station.
Medicines retain potency in space, study showsScience Recorder
Medicines do not seem to degrade faster in spacePhys.Org
Study: Medicines don’t degrade faster in spaceUPI.com