Venlafaxine at low dosages strongly inhibits serotonin, at moderate dosages also norepinephrine and only high dosages it also inhibits dopamine.

The ratio is the following.

  • serotonin : norepinephrine : dopamine
  • 1 : 30 : 93

According to the FDA data these are the percentages for side effects.

  • Libido decreased
  • Placebo 75mg 225mg 375mg
  • 1.1% 2.2% 1.1% 5.7%

Here are the results for other sexual dysfunctions.

  • Abnormal ejaculation/orgasm
  • Placebo 75mg 225mg 375mg
  • 0.0% 4.5% 2.2% 12.5%


  • Impotence
  • Placebo 75mg 225mg 375mg
  • 0.0% 5.8% 2.1% 3.6%

How would you explain the sudden drop of sexual dysfunctions at 225mg?

Other questions to consider:

  • Would a lower dose (37.5mg or 25mg) have sexual side effects (SSE) similar to placebo?
  • What dose has the lowest rate of SSE?
  • What is the lowest effective dose with reasonably low SSE?
  • How would adding of NDRI (bupropione) influence SSE given an increased dosage of venlafaxine? (i.e. Could one afford higher doses of venlafaxine with few SSE provided bupropion is taken concomittantly?)
  • $\begingroup$ Seeing as you asked a similar question a while ago at psychology.stackexchange.com/questions/21298/… are you in any position to write an answer to that question or is this one an offshoot after further research? $\endgroup$ Commented Jan 5, 2019 at 0:53
  • 1
    $\begingroup$ The difference between 2.2% and 1.1% may not be statistically significant. $\endgroup$ Commented Mar 18, 2019 at 0:02


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