Posted by S.D. on November 12, 2006, at 12:23:28
Is it dangerous to take diphenhydramine for insomnia while on Effexor (venlafaxine), Is it equivalent to taking a larger dose of Effexor. What I'm talking about is the fact that Effexor is metabolized mainly by CYP2D6, and diphenhydramine inhibits the activity of this enzyme.
The article http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11270914&dopt=Abstract ( or if that link isn't permanent then http://www.biopsychiatry.com/venbenadryl.htm) concludes "Clinically significant interactions could be encountered". When I read about Benadryl easing Effexor withdrawal I figured this accounted for it -- it causes the Effexor to diminish more slowly, which would also mean an effectively greater dose if you kept taking Effexor.
But on on the other hand the effect on Effexor would be the same as if you were, by genetics, a "poor metabolizer" of CYP2D6 -- and rxlist.com (http://www.rxlist.com/cgi/generic/venlafax_cp.htm, "Metabolism and Excretion" heading) states taht "The differences between the CYP2D6 poor and extensive metabolizers, however, are not expected to be clinically important because the sum of venlafaxine and ODV is similar in the two groups and venlafaxine and ODV are pharmacologically approximately equiactive and equipotent."
And my current doctor said there could be a significant effect only at uncommonly high doses of both substances (he is quirky, hard to figure, and it wouldn't be the first time to get bad advice from a good p-doc, but I'm not rocking the boat because he doesn't out of hand reject benzodiazepines (clon. for social phobia)).
I have periods of insomnia fairly frequently and Effexor can cause it too, so I need something I can safely take -- preferably without prescription so I can reliably take it as needed *when* I need it (2 weeks advance for dr. appointment doesn't help much, and anyway as I said, mine is hard to figure.)
thanks
- S.D. (shyInSanDiego)
poster:S.D.
thread:702828
URL: http://www.dr-bob.org/babble/20061110/msgs/702828.html