As I understand it, the problem is that a medication may be formulated
in more than one manner. For example, in the case of vitamins, at least
some of them are actually presented as precursors, I believe, and not
the vitamin itself (because the vitamin would be destroyed by digestion
prior to absorption). Those precursors might vary from one brand to
another, so standard trials are used to empirically quantify the
effects of the dose. I'm sure that Paul Trusten can tell us a lot more
about this.
Jim
On Fri, 01 Dec 2000, Dennis Brownridge wrote:
> I can understand that different substances, virus fragments, etc., have
> different relative physiological effect. This is a problem with some of the
> SI physiological units too, notably the sievert, which measures J/kg of
> radiation dose multiplied by some inscrutable "quality factor" that varies
> with the substance. But at some point in the manufacturing process, the
> medical industry has to measure the stuff somehow, regardless of what is in
> it, and they presumably do it by mass. Surely they are not counting out the
> molecules or virus fragments in every pill or dose. So couldn't we say that
> the IU is indirectly a measure of mass, with various mysterious "quality
> factors" multiplied in?
>
> > -----Original Message-----
> > From: Scott Clauss
> > >
> > Some vitamin and vaccine doses are measured by their biological activity,
> > which, in turn, does not directly relate to the mass of a
> > discrete compound
> > per unit volume (concentration), so it is impossible to give a exact
> > concentration for them in any metric units (or FFUs for that matter).
> > International Units (IU) are used instead. These are based on an
> > internationally agreed on biologicall effect or response. I
> > don't know what
> > organizations do this agreeing. Vitamins A, D and E are examples of this.
> > There are various forms of these vitamins with which the body can "do its
> > thing." Each has a different molecular weight so to get the same effect
> > would require different concentrations of each form. The vitamins you buy
> > are most likely mixtures of various forms. Vaccines are sometimes made of
> > busted up bits of viruses or bacteria. Some of these bits can evoke an
> > immune response, but trying to get a precise mass and therefore a precise
> > concentration based on which bits cause a immune response while
> > discounting
> > those that do not would not be useful.
> >
> > In short I think that dispensing vaccine by IU/mL does not disqualify
> > Australia from the fully converted side of the isle.
> >
> > Scott C
> >
> > > -----Original Message-----
> > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
> > > Behalf Of Paul Trusten
> > > Sent: Friday, December 01, 2000 2:33 PM
> > > To: U.S. Metric Association
> > > Cc: U.S. Metric Association
> > > Subject: [USMA:9489] Re: Australia not fully converted yet
> > >
> > >
> > > I'm not sure what an international unit is vis a vis SI, but it is not
> > > backward. It is a correct expression of a concentration, sayeth this
> > > apothecary.
> > >
> > > "Carter, Baron" wrote:
> > > >
> > > > Australia not fully converted yet. Its Quarantine and
> > > Inspection Service
> > > > still quotes vaccination doses in IU/ml
> > > >
> > > > http://www.aqis.gov.au/docs/anpolicy/dogcatapplication.pdf
> > > > <http://www.aqis.gov.au/docs/anpolicy/dogcatapplication.pdf>
> > > >
> > > >
> > > ------------------------------------------------------------------------
> > > > Name: Boomerang.gif
> > > > Boomerang.gif Type: GIF Image (image/gif)
> > > > Encoding: base64
> > >
> > > --
> > > Paul Trusten, R.Ph.
> > > 3609 Caldera Boulevard, Apt. 122
> > > Midland TX 79707-2872 USA
> > > [EMAIL PROTECTED]
> > >
> > >
> > > "No one from the Audubon Society has yet documented the
> > > finding of a modified barium swallow."
> > > --Byrd Ona Wyng, Forensic Ornithologist
> > >
> > > "Free Billy Rubin!" ---Medical Technologists' protest cry
> > >
> >
> >
--
James R. Frysinger University/College of Charleston
10 Captiva Row Dept. of Physics and Astronomy
Charleston, SC 29407 66 George Street
843.225.0805 Charleston, SC 29424
http://www.cofc.edu/~frysingj [EMAIL PROTECTED]
Cert. Adv. Metrication Specialist 843.953.7644
