There are substances (drugs, herbs, etc.) that induce or inhibit specific P450
enzymes. There are hundreds of these enzymes but humans have only 50, nine of
which metabolize drugs. Cytochrome P450 enzymes CYP3A4 and CYP2D6 biotransform
(i.e., metabolize/detoxify) more than 70% of the drugs/substances tested. For
example, cigarette smoke induces (speeds up) CYP1A2. Prozac (and many other
SRRIs) inhibit CYP2D6. Grapefruit juice inhibits the CYP3A4 enzyme which can
cause toxic levels of drugs that are also metabolized by CYP3A4 (such as Xanax,
caffeine, codeine, DHEA, erythromycin, Ambien, theophylline, etc.)
As far as I can tell, it doesn't make any sense to say that any substance speeds
up Phase I detox because no substance either affects all the P450 enzymes. Do
you know which of the P450 enzymes is affected by grapefruit seed extract
(active ingredient 'Citricide')? I couldn't find anything with a Google search.
Understanding which P450 enzymes metabolize specific drugs/substances has helped
me to understand my daughter's poor reaction to drugs and other substances.
Many things affect the expression of P450 enzymes (lack of certain vitamins,
iron deficiency, etc.) There are genetic tests for CYP2D6 because some people
lack this enzyme while others have low levels. According to
www.prozactruth.com, this test is used by Drug Companies to screen out
individuals that have non-performing or low levels of CYP2D6 from participating
in drug trials of antidepressants that are metabolized by CYP2D6.
More information at http://www.edhayes.com/startp450.html
>I have learned that grapefruit seed extract can affect Phase I of the liver's