Highlighting side effects, warnings, interactions, and more


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US brand name: Effexor
Generic name: venlafaxine

Effexor’s Potential Side Effects

Potential Side Effects All Crazy Meds Have

No matter which neurological and/or psychiatric drug you take, you’ll probably get one or more of these side effects. These will usually be gone, or at least will diminish to the point where you barely notice it most of the time, within a week or two.

  • Headache
  • Drowsiness / fatigue - even when taking stimulants in some circumstances.
  • Insomnia, instead of or alternating with the drowsiness.
  • Nausea
  • Assorted other minor GI complaints (constipation, diarrhea, etc.)
  • Generally feeling spacey / out of it
    • Which can all add up to the ever-helpful “flu-like symptoms” listed as an adverse event on the PI sheet of practically every medication on the planet used to treat almost any condition humans and other animals could have.1
  • All crazy meds can, and probably will affect your dreams as well. There is no way of telling if that will be good or bad, let alone if this side effect is permanent or temporary.
  • Any of the above side effects you see listed again below means they’re even more likely to happen and/or stick around longer and/or are worse than most other meds.

Typical Potential Side Effects

Although an SNRI, because its effect on norepinephrine usually isn’t noticeable until you reach a dosage somewhere north of 150mg a day, its initial, and mostly short-term, side effects are more like an SSRI. Not that there’s all that much difference between the two classes. So expect a few of:

headache, nausea, dry mouth, sweating, sleepiness or insomnia (with insomnia a little more likely), constipation or diarrhea (constipation is somewhat more likely), weight gain (although less likely and severe than most SSRIs), and assorted sexual dysfunctions. While sexual dysfunction is also a little less likely than SSRIs, some women will get a sexual boost at the higher dosages instead of a sexual dampening. It’s neither as frequent nor as pronounced (usually) as with the other SNRIs or the NSRIs (Strattera and reboxetine), but it does happen.

Sorry guys, but a higher dosage usually means whatever problems you had in that area will probably just get worse.

Uncommon Potential Side Effects

  • increased or lowered blood pressure
  • sweating
  • farting
  • anorexia
  • twitching
  • shock-like sensations (while you’re still taking it)
  • alcohol intolerance and/or alcohol abuse
    • making it just the thing to talk about at AA meetings

Freaky Rare Side Effects

  • Guys, if you thought everyone freaking out about the Lamictal Rash was bad, I have one word for you: balanitis.
  • Your hair may change color without Revlon.
  • Erotomania.
    • You know, I think that new hair color looks good on you…
  • Spontaneous orgasm.
    • OK, fine, take care of yourself then.

Not all side effects have been listed here, just the most likely and most interesting. For all reported side effects, see Effexor’s PI Sheet.

What You Really Need to be Careful About

By all that is holy, never just abruptly/suddenly stop taking it (going cold turkey), without an extremely good reason. Like a life-threatening allergic reaction, or you’re in a coma.

Pregnancy Category

C-Use with caution

Effexor’s Noted Drug-Drug, Drug-Food & Drug-Supplement Interactions

Effexor makes morphine less effective. This is a pharmacodynamic interaction (it happens in your brain) and not a pharmacokinetic one (one drug causes another to be metabolized faster or slower) like 95% of drug-drug interactions. Don’t read the study if you have problems with painful and, frankly, unnecessary animal testing.

Check for Other Drug-Drug, Drug-Food & Drug-Supplement Interactions Effexor may have at

Drugs.com’s drug-drug and drug-food interaction checker

It’s always a good idea to check for drug-drug interactions yourself. Just because most people in the crazy meds business know about really important interactions (e.g. MAOIs and a lot of stuff, warfarin and everything on the planet) doesn’t mean the person who prescribed your meds told you about them, or the pharmacist has all the meds you take at their fingertips like they’re supposed to. Or they have the time to do their jobs properly when not dealing with complete idiots or playing Angry Farmers on teh Faecesbooks.
Learn more about drug-everything interactions on our page of tips about taking crazy meds.

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« Effexor’s Uses and Using | Effexor’s Pros and Cons »

Pages and Forum Topics Google Thinks are Relevant to Your Mental Health

1 As well as being an indication of half of said conditions.

Last modified on Wed, 04 May, 2016 at 17:11:29 by JerodPoorePage Author Date created Monday, 25 April, 2011 at 11:53:36
“Effexor (venlafaxine) Pharmacology” by Jerod Poore is copyright © 2011 Jerod Poore Published online 2011/04/25

Effexor, and all other drug names on this page and used throughout the site, are the trademarks of someone else. Effexor’s PI Sheet will probably have the name of the manufacturer and trademark owner (they’re not always the same company) at or near the very bottom. Or ask Google who the owner is. The way pharmaceutical companies buy each other and swap products like Monopoly™ real estate, the ownership of the trademark may have changed without my noticing. It may of changed hands by the time you finished reading this article.

Page design and explanatory material by Jerod Poore, copyright © 2003 - 2016. All rights reserved. See the full copyright notice for full copyright details.
Don’t automatically believe everything you read on teh Intergoogles. No warranty is expressed or implied in this information. Consult one or more doctors and/or pharmacists before taking, or changing how you take any neurological and/or psychiatric medication. Your mileage may vary. What happened to us won’t necessarily happen to you. For more details see the Crazymeds big-ass disclaimer.

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