I did a bit of research into this today and came across some interesting info about tests done by the FDA for the US Dept of Defence in a program called SLEP.
The link is here but I've copied the SLEP info that I found interesting.
Do expired drugs lose their potency? Is it safe to take expired medications? Find out with this comprehensive guide about drug expiration dates.
www.drugs.com
Do expired medications lose their potency?
The best evidence suggesting that some drugs can last past their expiration date is from the Shelf Life Extension Program (SLEP) undertaken by the FDA for the Department of Defense.2,7,11
The original purpose of the SLEP program was twofold: to determine the actual shelf life of stockpiled military medications for future use, and to save government dollars.5
- Over 3000 lots, representing 122 different drug products, were assessed in the SLEP program. Potency, pH, water content, dissolution, physical appearance, or presence of impurities were assessed.
- Based on stability data, expiration dates on 88% of the lots were extended beyond their original expiration date for an average of 66 months. Of these, roughly 12% more lots remained stable for at least 4 years after the expiration date. Of these 2652 lots, only 18% were terminated due to failure.11
- Examples of common drug products that were tested with no failures included amoxicillin, ciprofloxacin, diphenhydramine, and morphine sulfate injection. Drug expiration extension dates on these products ranged from 12 months to 184 months (over 15 years).8 Biologics are not included in the SLEP program.
- Potassium iodide, which has been stockpiled in the US for a radiation emergency, has shown no significant degradation over many years.11
- In June 2020, FDA stated that expirations dates could be extended for certain stockpiled influenza antivirals such as Tamiflu (oseltamivir) 75 mg capsules and Relenza (zanamivir) if stored under labeled conditions and for emergency use in individual states.7 Expiration dates could potentially be extended for 15 years for Tamiflu and 10 years for Relenza.7
Also, testing reported in
The Medical Letter showed that many medications were still potent decades beyond their expiration dates. The authors note that there are no published reports of human toxicity due to ingestion, injection, or topical application of a current drug formulation after its expiration date.11
These results suggest that many drug products
may have extended shelf lives beyond their expiration date. However, it is difficult for any one consumer or health care provider to know which product in a medicine cabinet could have an extended shelf life or expiration date.
The ability for a drug to have an extended shelf life would be dependent upon the actual drug ingredients, presence of preservatives, temperature fluctuations, light, humidity, and other storage conditions. Additionally, the drug lots tested in the SLEP program were kept in their original packaging. Once a drug is repackaged into another container, as often happens in the pharmacy, the shelf-life could decline due to environmental variations.3
