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Anxiety and Stress Disorders

Metabolism and Processing Effexor

09/28/2005

Question:

I would like to know how long Effexor stays in a person`s bloodstream after they stop taking it. I was taking 100mg for over five years religiously for anxiety attacks. I have been off it for two weeks.

Answer:

There are two types of effexor (or venlafaxine), a commonly used anti-depressant and anti-anxiety medicine.  Regular or "short acting" effexor and effexor XR (or extended release).  An XR tablet is more slowly absorbed, so the medication more slowly gets into the blood stream and therefore the effect of a single pill lasts longer.

Once the medicine is absorbed, effexor is metabolized in the liver into another active medicine.  This means that as the medicine changes in the body, it stays active.  The "half-life" (the amount of time for half of the medicine to leave the body) of effexor is 5 hours, of its active changed medicine, 11 hours.  Therefore, when someone has been on this medicine regularly for more than a week, there is a "steady state", and the medicine level stays high in the body.

When you stop taking the medicine, it gradually leaves the body, and after just a few days, the level in the blood is quite low.  Within a week, almost all the medicine will be out of the body.

However, effexor and other antidepressants work by changing and adjusting brain chemicals.  Their effect on the brain chemicals (can neurotransmitters) can last for weeks, months, years and sometimes even be permanent. 

Hope that answers your question

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Response by:

Nancy Elder, MD Nancy Elder, MD
Associate Professor
College of Medicine
University of Cincinnati