Drug Expiration

[C2B2]

I like to ask my pharmacy to put expiration dates on my prescription medication bottles.  I have done this for years for my own protection after my uncle was given a bottle of morphine (he had lung cancer) that was expired.

I renewed my presciption for Metformin (500 mg, twice a day) which I take for PCOS and to prevent diabetes as I had gestational diabetes.  I do not have diabetes now.  When I renewed my prescription a new pharmacist was there.  I asked him to put the expiration date on my prescription bottle.  He gave me the date of December 2012 but then said that that date was only valid until the manufacturers bottle was opened.  He said that keep in mind that since he opened the bottle the medication was only good for three to six months.  That does not seem realistic to me since I used to take a small dose of dexamethosone which I used to get a years prescription all at once.  If what he said was correct then my medication would have been expired for at least half the time I took it.  In all the years I have asked for expiration dates on my prescription bottles, no pharmacist except this one has ever mentioned that the medication will expire three to six months after he gave it to me regardless of the manufacturers expiration date on the bottle.

I've read that drug companies put expiration dates on drugs as guidelines and that drugs usually last years after the expiration date with the exception of a few like tetracycline.  I am not looking to keep my drugs after my expiration date, I just want to know what information is correct as far as manufacturers expiration dates.

Thank you.

[Alison L, RPh]

You are correct. Expiration dates are mandated by the Food and Drug Administration to assure the products (medicine) made by the manufacturing companies are 100% effective until that date stamped on the bottle. It is true that the expiration date only applies to an unopened bottle packaged by the company but in pharmacies, to ensure that patients do not harm themselves or take medication that isn’t effective, the expiration date on the bottle given to the patient usually is before the expiration date stamped on the original manufacturer’s bottle. The medication is still good to use until the original expiration date on the manufacturer’s bottle. For example, if a medication bottle you had purchased over the counter said an expiration date of May 2011, the medication is still 100% effective until then, even if you opened it. The bottom line is the majority of drugs are effective until their expiration date but only if they are in the right conditions. A cool place, with not a lot of light, moisture or humidity would be an ideal place to store medication such as your metformin prescription. If other patients do not pay attention to where they store it, moisture and light could damage medication and therefore, make it ineffective even before the expiration date. Some medications have expiration dates that only apply as long as they are not open, but once they are open, it is only good for a certain amount of days for example, liquid antibiotics, or specific inhalers. In that case, the expiration date changes once the medication is open.