December 11, 2009
Expired Medications (or Medicines From The Mesozoic)
Every primary care physician occasionally encounters questions similar to the following.
“I just found some of my blood pressure medicines. The container fell behind the couch a year ago. The expiration date was last month. Can I still use them?”
“I know you just prescribed amoxicillin for my sore throat, but I just found some amoxicillin in my cupboard that I bought during the Nixon administration. Can I take that?”
The bigger question is, what happens to medications after they expire? Fortunately this issue of The Medical Letter reviews this ever-fresh topic.
The first reassuring fact is that medications are not more harmful as they degrade. So medicines don’t deteriorate into something toxic, just something ineffective. Any side-effects you get from taking an expired medicine are just the side-effects from the active medication, not from the process of degradation.
So all we have to worry about is whether the expired medication will still work, not whether it will harm us. The efficacy of medicines in tablets lasts much longer than that of liquid medications. Liquid medications that have become cloudy, discolored or have solid particles forming in them should not be used. The shelf life of eye drops is limited not by the stability of the medication, but by the preservative which eventually stops working and allows germs to grow in the solution. Epinephrine in epinephrine autoinjectors is particularly unstable and degrades shortly after the expiration date. Since epinephrine is a rarely-used but life-saving medicine, it should be replaced promptly at the expiration date.
Tablets on the other hand frequently retain most of their efficacy for years if kept in a dry location in reasonable temperatures. In their original unopened containers, many medications keep 90% of their potency 5 years after their expiration date.
So the recently expired blood pressure medications in the question above should be fine. The 35 year old amoxicillin is likely to be ineffective, but not toxic. And since amoxicillin is cheap, I would recommend purchasing a brand new twenty-first century batch.
A bright and joyous Hanukah to all my readers!
The Medical Letter article: Drugs Past Their Expiration Date (by subscription only)
Important legal mumbo jumbo: