From: dyer@ursolaris.spdcc.com (Steve Dyer)
Newsgroups: sci.med.pharmacy
Subject: Re: scopolamine vs ipratroprium bromide re: seasickness
Date: 4 Jun 1998 21:52:35 GMT

In article <35764BCF.2B0A@pacbell.net>, Bryan  <bryan459@pacbell.net> wrote:
>scopolamine is an anticholinergic and
>ipratroprium bromide is an anticholinergic
>
>scopolamine is useful in preventing sea sickness and
>IP is useful in treating bronchospasm
>
>what are the differences between the two agents that makes one
>(scopolamine) a good anti-seasickness medication, but the other
>(ipratroprium bromide) a
>never-mentioned-in-the-same-sentence-as-seasickness medication?

Ipratropium, the N-isopropyl quaternary amine of atropine, is endowed
with a permanent positive charge, and does not enter the CNS easily,
if at all.  Scopolamine is a tertiary amine, and does enter the CNS.
Anti-motion sickness agents largely work by their anticholinergic
actions on the vestibular system.

Another difference is that ipratroprium bromide is available only as a
metered-dose-inhaler.  Oral ipratroprium bromide would not be particularly
effective in treating bronchospasm, because you'd get terrible systemic
anticholinergic side effects from the dose necessary to relax bronchial
smooth muscle.  A MDI delivers the drug in a higher concentration to the
lungs.  Conversely, scopolamine (or atropine) might well be effective
as a MDI for chronic obstructive pulmonary disease, but you'd also risk
CNS anticholinergic effects.  In fact, inhaled anticholinergic drugs
are a very old application, since a common treatment for asthma in the
early part of the century was (of all things) cigarettes made of
stramonium, a herbal preparation containing atropine and related alkaloids,

--
Steve Dyer
dyer@ursa-major.spdcc.com