We have a patient with raised (6x the upper limit) urine normetanephrine. However, this patient had noradrenaline 5 days previous. The half-life of noradrenaline is very short (minutes)- but is metabolised to normetanephrine which is what we measure in our assay. Could this just be the drug?
Hi,
I found this
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2265.2011.04273.x/full
The half-lives of plasma free metanephrines
Kirsten A. Campbell, Shantha P. Joseph, Malcolm J. Whiting, Matthew P. Doogue, Clinical Endocrynology, Volume 76, Issue 5, May 2012
Free Normetanephrine should have half-life between 1 and 2 hours.
In general, only drugs which undergo specific organ partition (e.g. pesticides in the adipe) have long half lives (being "kidnapped and stored away", they do not undergo metabolism).
Thank you both, Fabrizio do you have the PDF?
Julia, the metanephrines were normal, but the normetanephrines were >6x the upper reference limit. Much more than we would expect to see in stress alone (even in ITU patients). No drug (other than above) indicated,
Many thanks
Tim
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