Posted by Larry Hoover on November 2, 2007, at 8:14:49
In reply to Is there conversion of Lyrica and Neurontin? 4-1?, posted by qbsbrown on November 1, 2007, at 18:18:48
> Or is it closer to 3-1. I know the max of Lyrica is 600mg, and Neurontin is around 3600-4800.
>
> I appreciate you all.
>
> BrianNo, there is no ratio that is useful. The problem is that Neurontin (gabapentin) does not follow a linear dose/uptake curve; the more Neurontin you take, the lesser the proportion making it into the bloodstream. One of the early selling points of Lyrica over Neurontin was its linear dose-uptake curve. Doubling the dose meant doubling the blood concentration, unlike Neurontin.
Based on the clinical trials for Neurontin, if you only took 900 mg/day, you'd get 60% of it, i.e. 540 mg. At 3600 mg/day, the true uptake is about 33%, i.e. only 1200 mg makes it into the blood. 4 times the dose, but only a little over double the uptake. 4800 mg/day has 27% uptake, so that's 1296. More than five times the 900 mg dose, but not even 2 1/2 times the uptake.
What this suggests is that the uptake mechanism is saturable, i.e. there is a maximum that can be taken up by the body, beyond which no increase in dose will have an effect.
Bottom line.....don't make dose comparisons. Compare response.
Lar
poster:Larry Hoover
thread:792786
URL: http://www.dr-bob.org/babble/20071027/msgs/792916.html