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Originally Posted by mr_colt  I see what you are saying but;
I don't know any clinical chemists and I have exhaustively searched the net but all the sites of interest are in other countries. I was just hoping someone on here might know where to point me to.
Or were you talking about the relevance between CYP2D6 and metabolism of codeine etc? From what I understand; CYP2D6 strips the methyl group off about 10% of the methylmorphine (codeine) turning it into morphine. Obviously people defficient in this enzyme will get little or no analgesic effect. Apparently it is required to properly metabolise a large number of drugs.
More information can be found here: CYP2D6 - Wikipedia, the free encyclopedia (yes i know its a wiki article but appears to be accurate.)
mr_colt. |
CYP2D6 metabolism may affect the metabolism of certain drugs, but to what extent is UNKNOWN. The other factor is that does this metabolism result in clinical significance? Probably not in most cases. For example, tricylic antidepressants are 2D6 drugs, metabolized through this pathway, but still work. The third issue is that WHY would we test for it? It would probably be an expensive test and not very cost effective especially for the NHS. Would it change the course of treatment by doing the test? If not, no need for the test. Codeine is a poor pain reliever, and better cough suppressor. Bottom line, it is never a first choice to treat chronic pain. If it is not working, it either means you have developed tolerance to it and must rotate to another opioid, it's not strong enough to begin with for the type of pain you are treating, or the type of pain you're treating is not best treated by opioids. Where we are concerned more about 2D6 is if a drug metabolized through this pathway, has this process inhibited or sped up with a concommitant drug that "induces' or "inhibits" CYP2D6. For example, if someone is on say fluoxetine (Prozac here) and amitriptyline or nortriptyline for sleep, headache or neuropathy, it is standard to check a "amitriptyline" or "nortriptyline" level if on a dose >50mg per day. This is because the CYP2D6 interaction may exacerbate the side effect potential of the tricylic because one "inhibits" and one is "metabolized" through this pathway. I don't think this will ever be a cost-effective choice to test for, because there are always other options to treat the same problem.