I would guess the main reason is that the tests to determine individual
patient response in oncology (and transplant medicine) are a fraction of
the cost of the medication, whereas in "general" medical practice it may
be the other way round. In this case the metaboliser status is often
seen as a safety issue handled conceptually as part of the total
patient safety management, employing qualitative decision-making -
something clinicians believe they are good at doing!
I hope to hear what other clinicians think.
Antoine van Gelder
*****************************************
Prof. A.L. van Gelder FRCP (London)
Head, Dept. of Internal Medicine
University of Pretoria and the
Pretoria Academic Hospital, South Africa
Tel 012 354-2287, Fax 012 329-1327
*****************************************
Graham Lewis wrote:
>
> Can anyone help explain why certain information important to successful
> drug therapy is not incorporated into medical practice? I am thinking in
> particular of the apparent non-acceptance of some forms of
> pharmacogenetic-based prescribing.
>
> For example, it has been known for many years that individual variations
> in genes (polymorphism) that encode and determine the activity of Phase
> I (e.g. 2D6) and II drug metabolising (e.g. n-acetyltransferase) enzymes
> are a major source of inter-individual variability in systemic exposure
> to drug doses. However, in contrast to other areas of clinical practice
> (such as testing to select patients for Herceptin therapy in breast
> cancer treatment), pharmacogenetic tests to identify gene varients in
> patients that influence the activity of cytochrome P-450 drug
> metabolising enzymes have not met with widespread acceptance, despite
> the demonstrated benefits and cost-effectiveness of such a strategy.
>
> The inconsistency in drug prescribing behaviour in this area, despite
> evidence of its rational basis, has been highlighted recently by the FDA
> in connection with the predicted upsurge in pharmacogenetics-based
> medicines (see e.g. LJ Lesko and J Woodcock, The Pharmacogenomics J.
> (2002) 2, 20-24). There may well be several issues here that serve to
> influence the acceptance or otherwise of such tests, and I would be
> extremely grateful for any ideas from list members as to why validated
> pharmacogenetics-based tests are routinely used in some areas of medical
> practice (e.g. oncology) whereas they are not in other areas (e.g.
> general practice).
>
> Graham Lewis
>
> --
> Dr Graham Lewis
> Science and Technology Studies Unit (SATSU)
> University of York, York YO10 5DD UK
> Tel: +44 (0)1904 433055 Fax: +44 (0)1904 433043
> email: [log in to unmask] www.york.ac.uk/org/satsu/
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