Posted by bleauberry on November 30, 2008, at 10:52:11
In reply to fluoxetine and norfluoxetine, posted by paulb on November 29, 2008, at 5:01:31
> does anybody know if norfluoxetine levels fall after ongoing treatment with fluoxetine because fluoxetine is metabolised to norfluoxetine by the CYP2D6 enzyme and they both inhibit this enzyme.
If they inhibit the enzyme, then levels should increase, right? Not fall? If the enzymes are inhibited, or slowed down, then drug levels should accumulate.
In any case, it is a built-in feature that is taken care of in regular dosing. It is already accounted for in the 20mg, 40mg, whatever, dosing size. In other words, while the enzymes may be slowed down by the drug itself, the increase of the drug is alredy built into the equation to where that increase is part of the overall desired picture. Does that make sense?
The effect is likely not profound. It is probably a consideration if taking a different medication that is also metabolized by that same enzyme, as the dose of the other medicine might have to be adjusted slightly lower. Probably not though, unless it was a critical med like for seizure or heart or transplant or HIV or something.
poster:bleauberry
thread:865692
URL: http://www.dr-bob.org/babble/20081123/msgs/865892.html