In our country the medicines are regulated by the Drugs and Cosmetics Act 1940 and rules 1945, amended from time to time. The regulation stipulates that every drug must have a date of expiry of potency, which indicates the date up to which the manufacturer guarantees the full potency and safety of the drug.
One study conducted by the US Food and Drug Administration, on the request of the US military concluded,“over 90 per cent of more than 100 drugs, both prescription and over-the-counter, were perfectly good to use even 15 years after the expiration date,” retaining most of their original potency.
Of course, exceptions prove the rule. There are drugs whose stability and potency decrease relatively faster e.g. nitroglycerine, insulin, liquid antibiotics etc.
Potency & Efficacy
The potency of drugs begins to reduce from the moment it is manufactured, this is called ‘drug decay’. So your medicine doesn’t become unusable at a particular hour.
Safety & Toxicity
Contrary to common perception and belief, there is hardly any scientific evidence that the expired drugs are toxic and, therefore, harmful.
The only report, in 1963, of human toxicity that may have been caused by chemical or physical degradation of a pharmaceutical product is renal tubular (kidney) damage that was associated with use of degraded tetracycline. Since then, tetracycline products have been changed to eliminate the problem. Not withstanding the fact that there are not many studies reported in this field, the lack of other reports of toxicity from expired medication is reassuring.