Posted by SLS on March 13, 2005, at 7:00:34
In reply to Re: Effexor XR vs Effexor Immediate Release » SLS, posted by gadman on March 12, 2005, at 21:40:14
> Thanks Scott... I just wish they made an 50 mg XR version... I wouldn't have to be messing with this...
> The answer lies in the below text... I am just trying to decipher it right now. Time to max concentrations for XR is 5.5 hours and 2 hours for immediate release... I am assuming that means XR is delaying the release only by 3.5 hours?
After reading this, I am under the same impression that you are. It looks like the XR version smooths things out a bit, but doesn't extend the time it spends in the body by much over the course of a day. However, for the immediate release version, the magnitude of peak concentration must surely be higher. Either you are reacting to a higher concentration of Effexor perfusing into brain tissues, experienceing withdrawal symptoms, or you are beginning to relapse into depression. Without knowing anything more about the history behind your treatment, this would be a difficult thing to guess at. I would try dosing 12 hours apart and see if things are made worse or made better. That will give you more information to work with.
- Scott
> -----------------------------------------------
> Administration of Effexor XR (150 mg q24 hours) generally resulted in lower Cmax (150 ng/mL
> for venlafaxine and 260 ng/mL for ODV) and later Tmax (5.5 hours for venlafaxine and 9 hours
> for ODV) than for immediate release venlafaxine tablets (Cmax’s for immediate release 75 mg
> q12 hours were 225 ng/mL for venlafaxine and 290 ng/mL for ODV; Tmax’s were 2 hours for
> venlafaxine and 3 hours for ODV). When equal daily doses of venlafaxine were administered as
> either an immediate release tablet or the extended-release capsule, the exposure to both
> venlafaxine and ODV was similar for the two treatments, and the fluctuation in plasma
> concentrations was slightly lower with the Effexor XR capsule. Effexor XR, therefore, provides a slower rate of absorption, but the same extent of absorption compared with the immediate release tablet.
poster:SLS
thread:470163
URL: http://www.dr-bob.org/babble/20050312/msgs/470344.html