Posted by Cam W. on November 17, 2001, at 15:37:50
In reply to Do benzos have a shelf live?, posted by nathan on November 13, 2001, at 20:48:30
> I was wondering if benzos like xanax (upjohn) and generic xanax lose potency over time.
Nathan - In Canada, at the expiry date medications (all medications) are presumed to have lost 5% of their listed potency. Drugs begin to slowly lose their potency from the time they are manufactured.
Many drug companies (I don't know which ones) will set their expiry date at approximately 3% of lost potency. This is to account for different rates of breakdown under different environmental conditions. For example, some drugs lose potency faster when stored under conditions of high heat &/or humidity, or if they are frozen.
By lawa (again, in Canada) pharmacists are not allowed to dispense medications that have passed their expiry date, or will not be all taken before the expiry date. Most pharmacies, including mine, will pull medications off of the shelf 2 to 3 months prior to the expiry date.
When I started in pharmacy over 17 years ago, many drugs and chemicals did not have expiry dates, due to their slow rate of chemical breakdown (eg. sodium chloride breaks down very, very slowly). Around the time that I graduated, the Canadian government had enacted legislation to ensure that all drugs and chemicals sold to pharmacies had expiry dates on the bottle. Usually this expiry date is approximately 5 years from the time of manufacture &/or bottling. Most simple chemicals still have not lost even minimal potency at this point.
I hope that this is of some help. - Cam
poster:Cam W.
thread:84157
URL: http://www.dr-bob.org/babble/20011113/msgs/84517.html