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On 3/4/96 Robert Wolov wrote:


>Just wondering... was any work done on a possible connection between
>using pseudoephredine and DCS?  Reason for asking: me and a buddy got
>bent on separate occasions while using sudafed, admittedly, we also
>had 'marginally' unsafe profiles and probably deserved it.  Dropped
>the drugs after that.

I've not seen the reports myself (probably won't help anyway since I'm
*not* a pharmacologist) but I believe there were reports by both DAN and
the IAND (anecdotal).

Since decongestants and antihistamines indirectly work on the linings of
blood vessel walls (the histamines directly effects the
endothelium...inner lining of blood vessels) which impact of
transmembrane exchanges, so reports of such associations are
"believable". We don't know exact mechanisms yet (to the best of my
knowledge) but I'm not "surprised" by such reports.

It would be nice if there were such formal studies in the dive community
like there are in the aviation community. But, commercial pilots
potentially could kill 200 people at a clip where divers drown alone, so
I suppose there just is not the motivation.


Robb W
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There are several important points in this discussion:

1. Allergic rhinitis results from release of histamine from sensitized mast 
cells.  Histamine, by stimulation of H1 receptors, cause endothelial cells to 
contract, and plasma and proteins leak from the intravascular space into the 
tissue (the source of the "stuffy nose").

2. Decongestants such as pseudoephedrine (Sudafed; a stereoisomer of ephedrine) 
and phenylpropanolamine are vasoconstrictors which increase circulating 
catecholamines.  Some of the "decongestant" activity may be due to constriction 
of the blood vessels and reduced blood flow to the tissue.  However, an 
important effect is also by stimulation of beta-1 receptors on mast cells,
which 
reduces mast cell release of histamine.  It seems intutitive that 
vasoconstriction could affect gas exchange in tissues.  Due to the increase in 
catecholamines, these drugs also have central nervous system effects similar, 
but less marked than, amphetamines.  So, in theory, there are a couple of 
reasons not to use these drugs while diving, but I have no hard data on whether 
or not they're really deleterious.  Remember, logic does not always equal truth.

3.  Antihistamines (H1 blockers; hydroxyzine (Atarax) and Diphenhydramine 
(Benadryl)) can also be used to alleviate effects of histamine release.  
However, these drugs also cause a fair degree of sedation.

As always, this is FYI
Eddie Brian

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