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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 7 of 7. This is the beginning of the thread.
Posted by Lin on September 30, 2000, at 12:20:12
I was recently started on 37.5 mg Effexor, which I take in the morning. I am wondering if the drug has a really short half life, or if I am imagining things, because I feel a slight crash from it when it wears off in the late afternoon. I get more anxious and restless and sort of agitated. Could this be from the medication wearing off?
Posted by stjames on September 30, 2000, at 14:10:48
In reply to Half-life of Effexor, posted by Lin on September 30, 2000, at 12:20:12
> I was recently started on 37.5 mg Effexor, which I take in the morning. I am wondering if the drug has a really short half life, or if I am imagining things, because I feel a slight crash from it when it wears off in the late afternoon. I get more anxious and restless and sort of agitated. Could this be from the medication wearing off?
James here.....Unlike most AD's Effexor has a very short half life, measured in hours, instead of the usual weeks. If you are not taking Effexor XR you should. I can get by with once a day dosing on XR
otherwise you would need to dose 2X a day. Effexor XR also has fewer side effects like nauesa.James
Posted by SLS on September 30, 2000, at 19:18:38
In reply to Re: Half-life of Effexor, posted by stjames on September 30, 2000, at 14:10:48
> > I was recently started on 37.5 mg Effexor, which I take in the morning. I am wondering if the drug has a really short half-life, or if I am imagining things, because I feel a slight crash from it when it wears off in the late afternoon. I get more anxious and restless and sort of agitated. Could this be from the medication wearing off?
>
>
> James here.....
>
> Unlike most AD's Effexor has a very short half life, measured in hours, instead of the usual weeks. If you are not taking Effexor XR you should. I can get by with once a day dosing on XR
> otherwise you would need to dose 2X a day. Effexor XR also has fewer side effects like nauesa.
>
> James
Hi guys.The half-life of Effexor (venlafaxine) is about 5 hours. That is very short for an antidepressant. Most are about a day or so. The only antidepressant that I am aware of for which the half-life is greater than 48 hours is Prozac (fluoxetine). Fluoxetine has a half-life of about 5 days. However, its active metabolite, norfluoxetine, has a half-life of anywhere between 7-15 days, the average being 9 days. One of the reasons why one must wait for between 4-8 weeks to fully evaluate its value is because it takes 4-5 weeks just to establish a steady-state blood level at any one dosage. Ouch.
Paxil (paroxetine) is another antidepressant that has a relatively short half-life. The average is about 11 hours. However, there are huge differences between individuals as to how long it can be. In some people, the half-life can be as short as 3 hours or as long as two days. Perhaps not surprisingly, the withdrawal syndrome seen upon the discontinuation of serotonergic drugs is worst for Effexor and Paxil.
- Scott
Posted by stjames on September 30, 2000, at 21:50:07
In reply to Re: Half-life of Effexor, posted by SLS on September 30, 2000, at 19:18:38
Thanks for being on the ball, scott. I was mixing the half lives, last detectable dose, and metabolites. If it were not for active metabolites
i would not have a life ! While on the subject of 1/2 lifes and Effexor, Effexor XR did not show an average half life much longer than the regular Effexor. It did show a less abrupt peak. My own observations are the the XR makes for less GI upset,longer action, less sweating, and less of the very weak rush I got right after I dosed. I had minor problems with regular Effexor, the sweating was the worst so I can see how this med
was difficult for normies. I have no side effects fron XR except a very slight increase in sweating. XR does not solve the issue of crashing if I miss a dose. It only lasts a day in me so it has never been a big deal.james
Posted by JohnB on October 2, 2000, at 22:53:31
In reply to Re: Half-life of Effexor, posted by stjames on September 30, 2000, at 21:50:07
> While on the subject of 1/2 lifes and Effexor, Effexor XR did not show an average half life much longer than the regular Effexor.
Wouldn't that imply that it would be better to take Effexor XR twice during the day, if the half life is 5 to 6 hours?
Posted by stjames on October 3, 2000, at 1:36:48
In reply to Re: Half-life of Effexor » stjames, posted by JohnB on October 2, 2000, at 22:53:31
> > While on the subject of 1/2 lifes and Effexor, Effexor XR did not show an average half life much longer than the regular Effexor.
>
> Wouldn't that imply that it would be better to take Effexor XR twice during the day, if the half life is 5 to 6 hours?James here.....
The short answer is yes, but remember this is half life and not last dectable blood level. I do fine on 1X a day dosing. I am considering 2X a day dosing now that I have no side effects from taking it. I used to get sweating and upset right after taking it so I only took it once a day to avoid problems.
james
Posted by Mark H. on October 3, 2000, at 20:47:26
In reply to Re: Half-life of Effexor, posted by stjames on October 3, 2000, at 1:36:48
I would just chime in with my usual litany that for those of us who are kept awake or suffer from achy, jumpy legs half the night when we take Effexor after about 2 or 3 p.m., it is MUCH better to take a single, largish dose after breakfast (to buffer your stomach) and to avoid the extended release version altogether. This accomplishes a couple of things: it lets the Effexor wear off quite a bit before trying to sleep, and for some of us who experience "mornings are horrible and I get better as the day wears on," the timing is right to help with depression. One caution: I have to be careful WHAT I eat for breakfast, or the food can bind the medication and I don't experience a full effect. Drinking lots of water seems important as well.
I'm glad to hear the XR version works well for others. You might plan on building up to 75 - 150mg a day before you get anything like continuous relief (in my experience).
Best wishes,
Mark H.
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