I have a bottle of Himalayan rock salt that expires on 29th Jan 2017.
Given that this rock salt has been hanging around for the last 250 million years, how does the act of putting it in a bottle cause it to go off within a couple of years?
The answer is it does not, it simply relates to our food and medicine packaging protocols.
When a manufacturer makes a new drug they need to make it up in a convenient form – usually tablets. Tablets have a Jekyll & Hyde personality requirement. Stick together in the bottle, fall apart fast in water.
Once an initial batch of pills has been made they undergo what is know as rapid stability testing and it’s really the stability of the tablets we are looking at. In the rapid stability testing they are warmed and cooled, humidified and dehumidified, exposed to light, etc to simulate daily use. 3 months testing gets you a 1 year shelf life, 6 months testing gets you a 2 year shelf life.
The current Sovaldi in use in Australia has an expiry of 9/2016 suggesting it was made 9/2014.
Almost all drugs are good for decades after their nominated shelf life has expired. If you’re interested to read more:
http://www.fda.gov/EmergencyPreparedness/Counterterrorism/MedicalCountermeasures/MCMLegalRegulatoryandPolicyFramework/ucm411446.htm