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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 6 of 6. This is the beginning of the thread.
Posted by jujube on January 10, 2005, at 23:28:48
Can somebody please tell me what P450 interactions are? I have been hoping to add Provigil to augment the Celexa I have been taking. I recently reviewed and gathered a lot of positive and useful information on the use of Provigil as an AD augmenter, but have just came across some additional information on Provigil which says that Celexa is a known compound with which Provigil has metabolic interactions. Can someone explain this to me, and, if possible, what effect combining the two might have? Would combining Provigil with Celexa render one or both ineffective or could the interaction cause unpleasant other side effects?
Thanks so much.
Posted by billybob42 on January 11, 2005, at 4:18:55
In reply to P450 Interactions?, posted by jujube on January 10, 2005, at 23:28:48
Posted by zeugma on January 11, 2005, at 5:13:36
In reply to P450 Interactions?, posted by jujube on January 10, 2005, at 23:28:48
P450 is the enzyme system that breaks down most psychotropics, thus enabling them to be excreted in a timely way. Provigil is an inhibitor of cytochrome 2C19, which is the enzyme responsible for citalopram metabolism (the metabolites are inactive, I think). So adding Provigil will cause plasma levels of citalopram to rise, theoretically. This isn't such a big deal as citalopram doesn't have the cardiotoxicity issues of the TCA's, which are the major target of concern in these interactions (people have died as a result of SSRI-TCA interactions, and the system was unravelled in much the same way as serotonin syndrome was discovered: because people were dying for no good reason). I don't mean to alarm you. High citalopram levels aren't going to cause these problems. And Provigil itself is not cardiotoxic, as far as I know: it is nothing like Ritalin, which in high doses is causing problems, which have caused me to lower nortriptyline to 50 mg/day.
Remember, last summer I was on 100 mg nortriptyline plus up to 150 mg Provigil and 10 mg Ritalin, and was engaging in strenuous exercise every day (and I am someone who has not exercised for many years). The interaction I read about in Provigil's PI sheet, about a rise in clomipramine levels, is worrying (in fact, I think it's the reason he preferred me on Lexapro than Anafranil: less potential for cardiotoxicity) but even so with proper monitoring such a combination could be used. The effect of Provigil might be that you would have to lower your citalopram dosage because of increased SSRI side effects. Of course, Provigil likely counters some of those anyway.
-z
Posted by jujube on January 11, 2005, at 23:45:40
In reply to Re: P450 Interactions? » jujube, posted by zeugma on January 11, 2005, at 5:13:36
Phew! That's a relief for me. I was worried that I might have to change ADs, and I am not up to that right now, (adjusting to one new med will be enough, for now at least). I think I am going to have to find myself something like a "Psycopharmacology for Dummies" to help me better understand these things.
Thanks for the info. Much appreciated.
Posted by jasmineneroli on January 12, 2005, at 1:29:21
In reply to Re: P450 Interactions? » zeugma, posted by jujube on January 11, 2005, at 23:45:40
Hi Tamara:
It's the dreaded CYP450 -2C19 that causes all my bad side effects!! I found this out after following an interesting thread here a few months ago.
The one common denominator between the drugs that gave me rotten (and identical) side effects was that they all were metabolized by 2C19.
I now avoid any drugs that require this liver enzyme to be processed. I'm either a slow metabolizer of 2C19 or lack the enzyme altogether.As Zeugma says, Provigil will probably enhance the action of Celexa, if you're metabolizing Celexa OK. (Like no side effects, and a therapeutic effect at "usual" dosage").
Below is a useful link to a cyp450 table and various drug/food interactions and genetic deficiencies. So you can check them out. Unfortunately, it's a little out of date, so Citalopram and Provigil are not listed, but there's good info there anyway.
Larry H. knows of others.
Good wishes,
Jashttp://www.anaesthetist.com/physiol/basics/metabol/cyp/cyp.htm#all
Posted by jujube on January 12, 2005, at 23:08:05
In reply to Re: P450 Interactions?, posted by jasmineneroli on January 12, 2005, at 1:29:21
It's the dreaded CYP450 -2C19 that causes all my bad side effects!! I found this out after following an interesting thread here a few months ago.
-- I had forgotten about that thread. Thanks for reminding me! I will re-read the posts for information.
> As Zeugma says, Provigil will probably enhance the action of Celexa, if you're metabolizing Celexa OK. (Like no side effects, and a therapeutic effect at "usual" dosage").
-- As far as I can tell, I am metabolizing Celexa ok. I had the usual start-up side effects, but those went away after a few weeks. And, it seems to be somewhat helpful with anxiety and ruminating thoughts.
> Below is a useful link to a cyp450 table and various drug/food interactions and genetic deficiencies. So you can check them out. Unfortunately, it's a little out of date, so Citalopram and Provigil are not listed, but there's good info there anyway.
-- Thanks for the link. I'll have a look at it. I'm trying to myself better informed about these things.
> Good wishes to you as well!
Tamara
This is the end of the thread.
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