A recent post that discussed, among other things, expired antibiotics generated a lot of comments. Some accused me of various things and stated their belief that expired drugs are fine and that requiring antibiotics to be prescribed is a global conspiracy. I’ll leave the conspiracy theory alone and just address the issue of expired drugs.

Expiry dates must be provided by manufacturers. They are essentially a guarantee that the stated level of active ingredient will be present at least until the expiry date. Drugs don’t instantly vanish the day after, but once you have passed the expiry date, you no longer can be certain about what is present. It’s possible the full amount is present, but it’s also possible that less is present, and it’s impossible to predict. If you don’t know how much is present, you can’t be certain that you are giving the proper dose. Giving inadequate doses is associated with treatment failure and increased likelihood of antibiotic resistance developing. Therefore, unless you have a pharmacology lab in your house (or readily accessible) to test expired drugs, you shouldn’t use them.

It’s not just my opinion.  Here’s what some other groups say on the subject:

Centers for Disease Control and Prevention (CDC): "…make sure you properly dispose of leftover and expired antibiotics."

University of Michigan University Health Service: "Do not take expired antibiotics."

The Alliance for Prudent Use of Antibiotics quotes Dr. Alfred DeMaria, an Assistant Commissioner at the Massachusetts Department of Public Health (MDPH) suggests that "stockpiling of antibiotics is strongly discouraged because it could lead to inappropriate patient decisions to self medicate, incomplete courses of antibiotics that might select for resistant organisms, the eventual use of expired medications, and the depletion of national supplies for medically-indicated uses. Antibiotics should be selected according to the specific infection of concern."

The advice from these respected groups, who have no financial stake in the sale of drugs, sounds pretty clear to me. Trying to save a little money by re-using expired antibiotics is a bad idea. The infection might get better, but it might not. If it doesn’t then the animal (or person) will be sick longer and may require more intensive (and expensive) treatment. If antibiotic resistance increases because of the use of inadequate doses, then more expensive drugs may be required and infections may be harder to treat. None of these are worth the potential cost savings.  This is a different situation than using expired drugs like painkillers for your headache. If those drugs are no longer effective, the worst thing that will probably happen is you won’t get better, which you would know in short order and be able to address. With antibiotics it’s harder to tell whether they are working early on during treatment (the critical time), and treatment failure could have much more serious consequences, both for the pet and for drug resistance.

When antibiotics expire, get rid of them.  Always complete prescriptions as directed and you won’t have leftovers to worry about.