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On Sun, 7 Jul 1996, Dunk, John wrote:

> I dont think you can apply this analogy in this way.The comparison of
> N2 absorption/elimination to drug absorption /elimination has some
> validity,but in the case of DCS,arent we talking about a mechanical
> process instead of a chemical one?

What's the difference? Like they say, you don't buy beer, you only rent
it.

> In the case of DCS,if you want to
> consider symptoms as a "toxic" reaction,these do not occur until you
> enter the elimination phase of the profile.For drugs,the toxic
> reaction occurs when you reach a range of accumulation or
> concentration in the tissues or blood.

So, how would you define differently the super-saturation of tissues with
nitrogen?

> I think maybe there may be some
> comparison if you think in terms of non-linear pharmacokinetics;that
> is,when some parameter of the elimination equation exceeds a certain
> value,elimination characteristics change drastically.

Now you're cooking!

> Just a bit of nitpicking here.The above corresponds to phase 2-4 of
> clinical testing .In phasme I,a drug is first tested etc. etc.

You are right. But in the last few years the FDA has allowed us to
collapse the process a bit; (Phase I+II, together; Phase II-III together)
not the least because the pharmaceutical companies drug patents have a
relatively short span.


> Depends on the drug some drugs have a *very* narrow therapeutic window
> (the range between efficacy and toxicity)like digoxin,where the normal
> serum levels are .001 to .002 mg/dl

Yes, but if nitrogen as any way that toxic, we'd all be plants.

> yes,but other factors may be as important or more so.If you want to
> use analogies,a more appropriate one might be protein binding.In this
> case,the drug as a greater affinity for a particular type of
> tissue/molecule.Binding reduces the amount of free drug in the
> system,causing a very large APPARENT volume of distribution.Factors
> that affect binding can cause a large change in the apparent volume of
> distribution,and therefor the amount of drug in the circulation.

So fine use another equation, but the concept is more knowledge through
application of *existing* science: down with empiricism.....and spelling
too.

I'll leave the next bit in, It still rules:
> >
> >I still think that the tables can be improved through the application of
> >other medical disciplines, anesthesiology, physiology, pharmacology. I may
> >be wrong, but I'll learn a lot trying.
> >
> >Safer diving through wiser physiology
> >

Peter H

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