Many medications do not come with a shelf life or expiration date obtainable from a pharmacist. It is assumed medications used in the relatively short time frame for which is is prescribed. That is not the case for MP patients whose antibiotics may last past a listed date.
Some pharmaceutical companies have supported initiatives for patients to discard medications if there is any doubt about safety or efficacy, because it may have expired. While research suggests that properly stored medications merely lose potency over long periods of time, it is not recommended that patients take medications past their expiration date. To prolong both their safety and efficacy, all Marshall (MP) medications should be stored in a cool, dry location.
The shelf life of medications is a matter of dispute with no clear answer. A large study of medications stockpiled by the military for decades revealed that most had not lost potency and were still safe well past the manufacturers expiration dates1). There were only a few (insulin, nitroglycerin and liquid antibiotics) that lost potency. None were deemed unsafe. A Medscape article reviews this study and others in greater detail.
Although older medication may be safe to take, in this litigious society, no medical professional is going to suggest a patient takes any medication that is listed as expired.
With regard to minocycline, the medication does not appear to degrade in air via oxidation – only water in a process known as hydrated oxidation. This is a problem with all the other MP antibiotics as well. One complication of taking antibiotics stored in a moist environment is Fanconi syndrome.