Hello, hope you guys are doing well. On rare occasion, sometimes with my Venlafaxine HCL (Effexor XR), i get some decently intense withdrawal symptoms around the time i take my next dose (2:15pm) and last for 2-3 hours. Symptoms being Brain zaps and nausea & anxiety.
my personal experience aside, my question is; is there evidence that exercise has a noticeable effect on the absorption of venlafaxine? If there is, would there be a recommended timing window to stay away from in terms of exercise vs medication timing?
thanks so much!
-Sam
Hey Sam,
This is a good question. Short answer: there’s no evidence that exercise changes venlafaxine absorption in a clinically relevant way, and the timing pattern you’re describing is more likely to be a sort of “end-of-dose” withdrawal rather than something exercise is doing to the drug.
On the pharmacokinetics question specifically: the limited literature on exercise and orally administered drugs suggests no substantial effect on absorption, and while exercise does reduce the blood flow to the gut, the resulting changes in oral drug absorption appear to be of minor clinical significance. Venlafaxine specifically has not been studied in an exercise PK trial that I’m aware of, so any answer is extrapolation. But there’s not really a plausible mechanism by which a workout would meaningfully delay or reduce absorption of an extended-release oral SNRI to the point of producing symptoms.
While Effexor XR is known for interdose discontinuation symptoms in some people, exercise may be an additional trigger for those symptoms in some folks.
Would recommend speaking to your provider about it!
Jordan
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Thank you very much for the detailed answer! I appreciate it.
If you are already taking the XR formulation and take consistently at the same time yet still experience those classic withdrawal symptoms, you would be warranted in still asking your provider about splitting the dose (ie 50% in am and 50% mid day). This would likely eliminate the withdrawal symptoms, if you can adhere to a split dosing schedule.