No announcement yet.

Shelf Life of Coumadin / Warfarin ?

  • Time
  • Show
Clear All
new posts

  • Shelf Life of Coumadin / Warfarin ?

    Does Coumadin / Warfarin lose potency over time?

    I have a bottle of 1 mg tablets that I use
    for 'adjustments' and / or backup in case
    my refill Rx is late in arriving. The expiration
    date was October 2006 (received in October 2005).
    Is it safe to 'assume' that the dose is still correct?
    How long does Coumadin remain 'safe / accurate'
    after it is made?

    'AL Capshaw'

  • #2
    Mine all come in packs with the expiry date on the end of the box. I just checked my vast supply of warfarin packs and some expire in 2007 and some as far ahead as 2011.

    I guess it really depends on when your pills were made, personally I wouldn't use a drug which says it has expired.
    Lithotripsy for kidney stones 8 December 2004.
    Began to feel unwell 19 December 2004, with hindsight, the beginning of endocarditis.
    Stroke 12 March 2005.
    Endocarditis diagnosed 16 March 2005.
    MVR/AVR - ATS 30 June 2005.
    Discharged 10 July 2005, taken ill on journey from hospital.
    Admitted to hospital 14 July 2005, complete heart block.
    Discharged from hospital 22 July 2005.
    Returned to work 9am on 7 November, dismissed 9am 7 November 2005.


    • #3
      The expiration date has almost nothing to do with the content of the pills. To get a drug approved, the manufacturer must show a minimum shelf-life. Obviously they do not want to put some on a shelf and wait 5 years to see if they decompose. So "experts" design some simulated shelf-life tests. The pills are exposed to more heat and humidity than normal and then these surrogate markers are extrapolated to a shelf life. It is also obvious that manufacturers do not want to put a long expiry date on the pills because people would keep them forever.

      Al's question is about something still being good two months after it "expired". The answer isn't really known. It depends on how they were stored. If they were in a place where they got direct sunlight - probably not. If they were in a refrigerator and were opened occasionally, they probably got moisture in the bottle and probably are no good. If they are in a pill bottle for a pharmacy, kept in a medicine cabinet and only opened occasionally - they are probably good. If they are in a sample pack from the manufacturer and were not exposed to excessive heat, they are probably still good. Properly stored, the left-overs from President Eisenhower's heart attack in 1955 are probably still good. They do not go sour like milk or turn into anything harmful, they just lose a little strength over time.


      • #4
        I work for a Class II Medical Device manufacturer and I can confirm what Al wrote. If people waited for actual aging data on a new drug, nothing would ever get launched to the marketplace. Therefore, "accelerated aging" tests are done to simulate the effects of time on a particular substance (performed pretty much how Al described). The effectiveness and accuracy of these accelerated aging studies is subject for a completely different discussion.

        The analogy to milk is a good one. If a carton has an expiration date of January 3rd, the milk inside is not good on the 3rd and magically turns to yogurt on the 4th. I regularly drink milk that is 5-6 days after the expiration as long as it hasn't gone sour. Unfortunately drugs typically do not "go sour" to give you a good indication of when they have turned bad. Aging for most drugs that I have worked with is pretty linear. That means that the compounds break down at a regular rate over time and the potency of the entire pill gradually diminishes. Therefore, a pill taken during the expiration month has virtually the same potency as it would one month after expiration.

        There is another component of shelf life that is worth mentioning as well, and that is Marketing. If generic Warfarin had a shelf life of 2 months, and the brand-name Coumadin had a shelf life of 4 years, would anyone buy the generic? Also, what's the benefit for the makers of Coumadin showing that their drug has a shelf life of 5 years instead of 4 years? If you leave it at 4 years, most people will clear out whatever they have when it expires and buy a new bottle. Obviously this results in higher sales of the drug over the long term. All of these things and more are discussed when a company decides the shelf life of a drug.
        Mitral Valve Repair 12/9/05 with Dr. Laks at UCLA.


        • #5
          Thanks ALL for your replies and information.

          Guess I will start using my 1's and 3's to make up my daily dose of 4 mg, just to 'get my money's worth.

          'AL Capshaw'