Quote:
Originally Posted by wet dog
I have been studing the efficacy of many household meds, after 1 year, (stored in dry cool places), most retain a reliable strength of 85%, can I assume that is correct?
WD
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The FDA defines an expiration date as “the date placed on the container/labels of a drug product designating the time during which a batch of the product is expected to remain within the approved shelf life specifications if stored under defined conditions, and after which it may not be used.”
I seem to remember hearing the 85% in school referring to how most products must remain at AT LEAST 85% potency at the end of the expiration dating in order to market the product with that specific shelf life. For example, if my 81mg aspirin is dated 6/2010, then it must have at least 68.85mg active product in it by the end of June 2010. However, each product has different potency limits on it that are set by the United States Pharmacopeia (USP). Looking into it now, it would seem most products have a tighter lower potency limit of 90%.
However, just because this is the minimum potency level does not mean that the product must be at 90% potency by the expiration dating. In fact most medications are stable far longer than the dating would imply. The DOD/FDA runs a program called the Shelf Life Extension Program (SLEP) and they found that "84% of 1122 lots of 96 different drug products stored in military facilities in their unopened original containers would be expected to remain stable for an average of 57 months after their original expiration date". Some antivirals stayed stable for 25
years post expiration date.
http://www.medicalletter.org/freedocs/expdrugs.pdf
However expiration dating is different than "beyond use" dating. "Beyond use" dating is what pharmacists use when filling prescriptions from the sealed manufacturer approved bottle into the pharmacy's vials. USP guidelines dictate that beyond use dating be either 1 year or the manufacturer's listed expiration date, whichever is sooner. There is very little data on extending the beyond use dating on drugs due to the differences in how medications are dispensed. For this reason, I would feel much safer using expired medications in a bottle sealed by the manufacturer than I would in one packaged by the pharmacy.
Levothyroxine (Synthroid) used to have limits of 90%-110% by the end of expiration dating before 2009. However due to the following data collected by the FDA:
http://www.fda.gov/ohrms/dockets/AC/...y%20slides.pdf
It amended it limits to 95%-105%:
http://www.fda.gov/Drugs/DrugSafety/.../ucm161257.htm
The USP issued the new monograph after the 2 year transition period required by the FDA:
http://www.usp.org/USPNF/notices/iraLevothyroxine.html
The take home point for me is that levothyroxine (Synthroid and others) has proven stability issues that prompted the FDA to take this action and I would not count on much of an extended shelf life beyond expiration dating for this particular medication. Especially given the relatively narrow therapeutic index.
To comment on the fine MDs comments on how to extend your stock, I would personally choose the easiest path and get your physician to write for a 30 or 90 day supply and use one of the pharmacies with the $4/$10 prescription program. This would be outside of insurance, your insurance would come back "refill too soon" and the pharmacy would not fill it. Just tell them you will pay cash, and it will only be $4 or $10. The pharmacy may be hesitant to fill it if you are using the same pharmacy that you normally receive the medication at, but I would just explain it is for an emergency stock and you plan on rotating out expired meds. If they still give you trouble, find another pharmacy. Also, check to see if you can get it in the original packaging. You may get an extended expiration date than you would if the pharmacy filled it due to "expiration date" vs "beyond use date". You could ask the pharmacy to fill it with their longest dated supply as well. Most pharmacies use up their "short dated" product first in order to not waste it.
Good luck
SR