Posted by Larry Hoover on June 27, 2007, at 19:20:38
In reply to Re: high dose lithium » big time, posted by Squiggles on June 27, 2007, at 6:22:07
> Hi,
>
> I wonder what your lithium dose is?I wonder why you think it matters? We've been over these concerns before, and I must reiterate that your attitude towards the use of lithium might be dangerous if adopted by other persons.
The very same lithium dose, when taken by different individuals, will result in different blood lithium concentrations. That is why lithium is never titrated by dose, but instead, by blood concentration.
> I take 900mg per day-- i would prefer lower but my dr. wants the blood level where it is 0.8-1.2.
That is the normal therapeutic blood concentration. The dose that gets you there is idiosyncratic, although your dose is rather typical, nonetheless.
> The narrow therapeutic index: ah, yes, well after many yrs. of experience, i would say that it depends very much more on dietary and sodium/potassium/water balance. cumulative toxicity AND interaction with other drugs.
More so than dose? Not true. These latter variables influence the blood concentration, absolutely, but they are lesser management factors than is dose itself. In an individual, blood concentration is linear with dose.
> I think that it being such an old drug, it has been monitored for this danger, far more than other drugs which also have a toxity level. "Narrow" is a vague concept when it is not given in actual numbers, and all that is indicative is the actualy toxicity after the fact.
There is nothing at all vague about the narrow therapeutic index issue for lithium. It has an index of 2.
From the monograph:
"Adverse reactions may be encountered at serum lithium levels below 1.5 mEq./l. Mild to moderate adverse reactions may occur at levels from 1.5 to 2.5 mEq./l., and moderate to severe reactions may be seen at levels of 2.0 mEq./l. and above.
Diarrhea, vomiting, drowsiness, muscular weakness, and lack of coordination may be early signs of lithium intoxication, and can occur at lithium levels below 2.0 mEq./l. At higher levels, ataxia, giddiness, tinnitus, blurred vision, and a large output of dilute urine may be seen. Serum lithium levels above 3.0 mEq./l may produce a complex clinical picture, involving multiple organs and organ systems. "
In the standard practise of medicine, the occurrence of moderate to severe toxic reactions at 2.0 mEq./l, with therapeutic levels arising in and around 1 mEq./l, the therapeutic index (the ratio of toxic dose to therapeutic dose) is 2.
Lithium toxicity is no joke, and is not the least bit overstated.
Lar
poster:Larry Hoover
thread:766032
URL: http://www.dr-bob.org/babble/20070622/msgs/766276.html