Posted by Larry Hoover on May 24, 2006, at 19:16:58
In reply to Re: Why doesnt anyone talk about Lithium? » UgottaHaveHope, posted by Squiggles on May 22, 2006, at 6:52:44
> I think drs. may find the regular blood tests required for lithium "cost-ineffective", but i have a hunch that the need for them is historically exaggerated.
The toxicity of lithium is not all exaggerated. It is precisely the problem.
Lithium is one of the "drugs" with one of the smallest therapeutic indexes of all drugs. I put 'drugs' in quotes because it's not a drug at all, except in how it's used. It's an ion, found in low concentration in the environment. It's a salt, in its natural form.
Therapeutic index is technically the ratio of LD50 to ED50, which, in layman's terms, is the ratio of toxic dose to therapeutic dose.
Lithium is considered to be an NTI (narrow therapeutic index) drug, and its use requires very close monitoring. Every health authority in the world, (FDA, Health Canada, etc.) publishes annual lists of NTI drugs, and lithium will always appear on that list.
Every person's kidneys handle lithium a little differently than everyone else's. The therapeutic dose is that dose that maintains a stable blood concentration, balanced by intake and excretion in urine. Although the blood concentration that is effective is similar for all people, the dose that maintains that concentration can vary from 300 to 2700 mg/day. Moreover, chronic lithium use changes how the body manages lithium. Over time, the intake dose generally needs to be reduced.
But all of this data that is required to manage lithium can *only* be obtained by sampling blood.
That's what makes lithium a "high management" drug, from a doctor's perspective.
Lar
poster:Larry Hoover
thread:646452
URL: http://www.dr-bob.org/babble/20060520/msgs/648031.html