From the story here:
Numerous studies on expired, properly stored drugs, mostly pills, have found them fully potent or close, some many years after that date. In one case, unopened bottles of painkillers, antihistamines and other drugs from the 1960s were still very potent when tested a half-century later. ... The exceptions are aspirin and the antibiotic tetracycline, which can deteriorate soon after expiration dates. ... But experts say don't use expired liquid medicines, insulin and other injected drugs that must be refrigerated. They can break down faster than pills, especially if they aren't kept cold. Ditto for drugs not properly stored. Medicines kept in areas with high humidity or fluctuating temperatures — like a bathroom cabinet — or left in direct light degrade faster and can lose potency. Instead, keep them in a cool, dark place, advises Michael Gaino of the American Society of Health-System Pharmacists.
