Metabolite question

  1. Also posted in Renal/Dialysis Nursing

    I have had some questions about the use of Darvon in patients with renal insufficiency (also the elderly). I have heard that the metabolites can build quickly in this population and cause problems. Can anyone help me with general information or resources?

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    About mattcastens

    Joined: Sep '01; Posts: 273; Likes: 31


  3. by   Jenny P
    Geez, Matt, I thought this was related to your "setting a bad example" thread and I was going to give you a hard time about dietary supplements!
  4. by   mattcastens
    No, Jenny, that would be a question about Metabolife, not metabolites.
  5. by   TracyB,RN
    Well, I have seen a generic Metabolife supplement called, you guessed it, "Metabolite".
  6. by   P_RN
    Not just renal patients I'd say. Propoxyphene AND Meperidine both do a job on older systems with their breakdown or lack thereof. Plus if you add any APAP to Darvon then you have another problem. Both should be avoided.
    Though I will say I have seen many older ones who just loved their Darvocets. And many doctors who are all too happy to supply them.
  7. by   Q.
    HA! Matt I thought it was about skinny pills too!

  8. by   aimeee
    I've been told that too, Matt, by pharmacists, physicians, and nurses who were expert in pain management. I've been searching for a web site that explains it well but its usually just stated as a general warning. This is the best I've found so far:

    Darvon, Darvocet

    "Metabolite norpropoxyphene has 1/2 life of 30-36 hours Norpropoxyphene is the metabolite and its
    accumulation with repeated doses may be responsible for some of the observed toxicity.
    Norpropoxyphene the active metabolite has local anesthetic effects and like lidocaine, may cause cardiac conduction delay (increased PR interval and QRS prolongation)."

    "Bioavailability reduced 30-70% due to extensive 1st pass metabolism. 80% of drug is bound to plasma proteins and stored in fatty tissues. Great variability between people in the rate of clearance and plasma concentration. Crosses the placenta."

    With a drug half life of 6-12 hours, and a metabolite half life of 30-36 hours, you can see the potential for problems, especially in people who have any sort of compromised ability to clear it.