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Venlafaxine: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Oct 3, 2019.

1. How it works

  • Venlafaxine may be used in the treatment of depression. Experts aren't exactly sure how venlafaxine works but believe its effects may be due to its ability to block the reuptake of serotonin and norepinephrine, and to some extent dopamine, three neurotransmitters in the brain associated with depression.
  • Venlafaxine belongs to a group of medicines called Selective Serotonin and Norepinephrine Reuptake Inhibitors (SSNRIs).

2. Upsides

  • Used for the treatment of significant depression (Major Depressive Disorder).
  • Generic venlafaxine is available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Nausea, headache, sedation, dry mouth, dizziness, insomnia, nervousness, constipation, and sweating are some of the more commonly reported side effects. May also cause weight loss, cholesterol elevation, sexual dysfunction, and several other side effects.
  • May be associated with a sustained, moderate increase in blood pressure (about 10-15mm Hg) in some people; regular monitoring of blood pressure may be required.
  • As with other antidepressants, venlafaxine may increase the risk of suicidal thoughts or behavior in young adults. Not generally recommended for people under the age of 18.
  • May impair judgment or cause drowsiness and affect a person's ability to drive or operate machinery. Avoid alcohol.
  • In susceptible people, pupil dilation may lead to an episode of angle-closure glaucoma.
  • Interaction or overdosage may cause serotonin syndrome (symptoms include mental status changes [eg, agitation, hallucinations, coma, delirium], fast heart rate, dizziness, flushing, muscle tremor or rigidity and stomach symptoms [including nausea, vomiting, and diarrhea]).
  • May increase the risk of bleeding, especially if used with other drugs that also increase bleeding risk.
  • May precipitate a manic episode in people with undiagnosed bipolar disorder.
  • May cause a lowering of sodium levels in the body (this is called hyponatremia). Elderly people or people taking diuretics or who are already dehydrated may be more at risk.
  • May cause a discontinuation syndrome if abruptly stopped; symptoms include flu-like symptoms, irritability, low mood, dizziness, electric shock sensations, a headache, and confusion.
  • Rarely causes seizures.
  • May interact with some other medications, including other antidepressants and those metabolized through CYP3A4 or CYP2D6 enzymes, although the degree of interaction appears smaller than with some other antidepressants.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

4. Bottom Line

  • Venlafaxine is an antidepressant that may cause a discontinuation syndrome if abruptly stopped after long-term administration.

5. Tips

  • Take with food.
  • Be alert for changes in behavior including agitation, depressed mood, and suicide-related events and seek medical advice if changes are apparent.
  • Do not drive or operate machinery until full effects of venlafaxine are known as it may impair your judgment and affect your ability to drive or operate machinery.
  • Swallow extended-release capsules whole; do not break, crush, or chew or attempt to dissolve in water. If you cannot swallow the capsule whole, the capsule may be opened and the contents sprinkled over a spoonful of applesauce and swallowed without chewing.
  • Seek urgent medical advice if symptoms consistent with serotonin syndrome (such as agitation, hallucinations, fast heart rate, dizziness, flushing, nausea, or diarrhea) develop.
  • Alcohol is best avoided when taking venlafaxine.
  • Do not stop taking venlafaxine suddenly. Your doctor will advise you how to taper it when the time comes to discontinue it.
  • Seek urgent advice from an eye professional if eye pain, changes in vision, or swelling or redness around the eye develop.

6. Response and Effectiveness

  • Peak plasma concentrations occur within one to two hours of taking an immediate-release tablet; however, it may take two to four weeks before a reduction in depressive symptoms is noticed, and up to six to eight weeks before the full effects are seen.

7. Interactions

Medicines that interact with venlafaxine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with venlafaxine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with venlafaxine include:

  • anti-anxiety medications, including other benzodiazepines, such as diazepam and oxazepam
  • anticoagulants such as warfarin
  • anticonvulsants such as phenytoin
  • antidepressants, such as amitriptyline, imipramine, nortriptyline
  • antihistamines that cause sedation, such as diphenhydramine
  • antiplatelet agents, such as aspirin, apixaban, clopidogrel, and NSAIDs
  • aprepitant
  • duloxetine
  • HIV medications such as indinavir
  • linezolid
  • methylphenidate
  • migraine treatments, such as rizatriptan and sumatriptan
  • monoamine oxidase inhibitors, such as selegiline, isocarboxazid, or phenelzine
  • omega-3 fatty acids
  • opioid analgesics such as oxycodone and morphine
  • muscle relaxants such as cyclobenzaprine
  • serotonin modulators, such as nefazodone and trazodone
  • sleeping pills, such as zolpidem
  • some chemotherapy treatments
  • some heart medications, such as doxazosin and prazosin
  • some medications used to treat mental illness, such as aripiprazole, clozapine and thioridazine
  • voriconazole.

Alcohol may worsen the side effects of venlafaxine such as drowsiness, dizziness, and liver toxicity.

Note that this list is not all-inclusive and includes only common medications that may interact with venlafaxine. You should refer to the prescribing information for venlafaxine for a complete list of interactions.


Venlafaxine. Revised 06/2019.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use venlafaxine only for the indication prescribed.

Copyright 1996-2020 Revision date: November 20, 2019.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.