From: waanders@umich.edu (Nick Waanders)
Subject: Re: Antihistamines and Decongestants
Date: Thu, 01 Oct 92 00:44:45 EDT
Organization: University of Michigan
Followup-To: sci.med
Distribution: usa


> > Are there some bad side effects of regularly taking antihistamines
> > and/or decongestants?
> 
> 
> I wonder that, too.  For example, do decongestants contribute to 
> the incidence of kidney stone attacks in those of us prone towards them?
> We're supposed to drink lots of water to keep down our uric acid 
> and calcium levels.  It would seem that by drying us out, decongestants 
> would allow those levels to increase, helping more stones to form.
> 
> I also wonder about the LONG-TERM affects of taking antihistimines
> and decongestants.  Is anyone aware of any studies?

Some information....
1) Decongestants are predominately sympathomimetics, which means they
elicit a physiologic response similar to the sympathetic nervous
system - best known for the "flight or fight" response.  With respect
to nasal decongestion, constriction of perpheral blood vessels will
decrease secretions in the sinuses and lead to decongestion.  My
notes suggest that they are typically topical (ie. sprays).  Examples are
phenylephrine and ephedrine.  Unwanted effects could include cardiac
irregularities, generally associated with excessive dosages.  One aspect
to be aware of is "rebound congestion".  Discontinuing decongestants after 
chronic use will lead to a slightly higher than normal vasodilation and
congestion.

Antihistamines block the action of histimine which causes broncho-
constriction, gastric secretion (h1 receptors), vasodilation and increased
vascular permeability.  Antihistamines can be targeted to h1 or h2
receptors, so the h2 antihistamines selectively block histamine
mediated gastric secrection (good for ulcers, eg cimetidine).  For h1
receptors,
histamine is released in resonse to local injury and exposure to specific
antigens.   The primary side effect is sedation, but new antihistamines
(eg. seldane) are non-sedating.  If sedation is a problem, I suggest trying
different 
preperations or lower doses.  Chlopheniramine (as in Chlor-Trimeton) 
works well for me without the sedation.  Find one that works well for you.

In light of this information...
1)  Antihistamines and topical decongestants in normal dosages should
not (for any practical purposes) alter system water/electrolyte (sodium,
calcium, potasium) balances.  High water intake prevents kidney stones by 
maintaining dilute urine.
2)  Because antihistamines are specific for cells which have receptors
for histamines, it seems unlikely taking them for long term will cause
problems.  Decongestants, as simpathomimetics, might be different, but
I have not read anything discouraging long term usage.  For rhinitis,
allergies, etc. I would stick with antihistamines.
3)  It is difficult to investigate long term effects of any drug because
of the mechanics of controlling for confounding influences, such as other
medical conditions, changes in the medications taken, discontinuation
of medications, objective measures, etc.  I've taken antihistamines for 
10 years, but I take them seasonally and I don't hesitate to try new 
preperations.  I have had no side effects other than sedation and excessive

mouth/eye dryness, which are dependent on the preperation and the dosing.
I have been told that an allergy specialist here at UofM has been taking
antihistamines for over 20 years without side effects.

Nick Waanders
University of Michigan