Venlafaxine (Effexor)

Nadia Whiston
Author: Nadia Whiston Medical Reviewer: Amy Shelby Last updated:

Venlafaxine is a medication that can be ordered by prescription only. Belonging to a family of antidepressant drugs named selected serotonin and norepinephrine reuptake inhibitors (SSNRIs)[1], Venlafaxine operates by encouraging the brain’s production of the naturally positive, mood-enhancing chemicals serotonin and noradrenaline[2]. Available in either oral tablets or capsules, Venlafaxine is used to treat anxiety, manic depression, dysphoric moods, and panic attacks.

Venlafaxine brand names

  • Effexor XR
  • EFFEXOR[1]

What is venlafaxine prescribed for?

Venlafaxine is prescribed for those who suffer from generalized anxiety disorder, dysphoric moods (feelings of discontent, disassociation, or indifference to the world around them), depression, and social anxiety disorder – psychiatric disorders that interfere with day-to-day living and working[3].

Venlafaxine has also been used for women who are being treated for breast cancer or to ease ‘hot flashes’ (sudden and extreme changes in body temperature and sweating), which many women experience during the menopause[3]. It can also be prescribed for severe premenstrual cycle depression, OCD, and PTSD[4].

How does venlafaxine work?

Venlafaxine increases and supports levels of serotonin, norepinephrine, and dopamine in the brain. Serotonin is created by your nerve cells, but can also created in different parts of the body, including the stomach. Serotonin enables us to experience happiness and helps us to sleep, heal our wounds, and regulate anxiety[8].

Venlafaxine not only encourages the body to create more serotonin, norepinephrine, and dopamine, but it also protects them by blocking transport proteins from breaking down or reabsorbing these chemicals. In doing so, this keeps a higher level of these chemicals available to the brain. This is important, as it helps us to remain mentally balanced.

How is venlafaxine usually taken?

Take Venlafaxine exactly as your doctor or healthcare provider has directed. Do not increase or suddenly decrease your prescribed daily dose. Venlafaxine is typically taken two or three times a day with food. If you are taking an extended-release capsule, this is taken once a day, either in the morning or evening with a meal.

You should try to take your tablet at the same time every day. You should not chew, crush, split or try to dissolve your tablet in water; it should only ever be swallowed[3].

How long does venlafaxine stay in your system?

The average afterlife of venlafaxine in the body is slightly less than two days, which is very short. Of course, how long it takes to leave your system entirely is different for every person and dependent on various individual factors, specifically liver functionality, body composition, genetics, and age.

Unlike other anti-depressants, the half-life (the amount of time the body takes to break down half a dose) of Venlafaxine is five hours, give or take. In the case of venlafaxine, the body can break it down very quickly, which means that withdrawal symptoms from the drug may be experienced if just one dose is missed[9].

Venlafaxine side effects

You should seek immediate medical help if you believe you have had an allergic reaction to Venlafaxine. Symptoms of an allergy can be difficulty breathing; a rash or sudden hives; or swelling of the mouth, throat tongue, or lips. Allergic reactions can be fatal so do not ignore them or wait for symptoms to pass.

Many medications provoke an adverse response from the body. Some can be serious, though many are minor and will improve gradually as the body adjusts in the initial stages of treatment[2].

Common side effects of venlafaxine reported in 1 in 100 people are as follows:

  • Dry mouth
  • Constipation
  • Finding it difficult to sleep or switch off
  • Feeling dizzy lightheaded or sleepy
  • Experiencing headaches, sweating, or hot flashes
  • Decrease in libido, inability to achieve orgasm in females, inability to sustain an erection/ejaculation in males[3]

If any of the above really bother you, speak to your doctor or pharmacist.

There are rare but more severe side effects reported by less than 1 in 100 people when taking venlafaxine. Call your doctor if you experience[1] [2] [3]:

  • Anxiety attacks
  • Sudden mood or behavioral changes
  • Increased impulsivity, hostility, aggression and more intense feelings of depression
  • Confusion or memory loss
  • Changes to your nervous system (i.e., increased heart rate or sensations like tremors or feeling like you are weak and may faint)
  • Nose bleeds or bleeding gums or coughing up blood
  • A notable change in your usual menstrual cycle (e.g., sudden heavier periods, bleeding between periods, spotting or vaginal bleeds)
  • Sudden weight gain or weight loss
  • Coma of loss of consciousness for a period of time
  • Small purple spots on skin
  • Chest pain
  • Abdominal pain

It is also important for patients taking venlafaxine to be aware of serotonin syndrome, which has the following symptoms[1]:

  • Fever, sweating, twitching, shivering, vomiting, and fast heart rate
  • Impairedcoordination
  • Hallucinations
  • Nausea and diarrhea 


*As every individual’s experience of the drug is different, venlafaxine may cause other adverse effects that may be specific to you. Keep in contact with your doctor while taking your prescription and report anything unusual that you experience.  

*Children can be especially sensitive to this drug,Aand side effects such as weight loss may be quite obvious. Venlafaxine may also inhibit their growth/ height[3].

*Older adults can be especially sensitive to certain side effects of the drug, especially dizziness when standing and bleeding. They are also more likely to experience a salt imbalance, which can in turn increase the risk of falling[5][6].  

Venlafaxine precautions

Most adults can take venlafaxine; however, some conditions must be discussed with your doctor before embarking on a course of treatment.

For those who suffer from diabetes, increased vigilance is required because venlafaxine can alter your blood sugar levels, making it more difficult to remain stable. It is thus suggested that for the few first weeks of venlafaxine treatment, patients monitor their blood sugar levels so that if adjustments to their treatment are necessary, they can be identified as soon as possible.  

Other individual factors that must be considered before embarking on a course of venlafaxine are as follows[3] [2]:

  • If you are taking a monoamine oxidase inhibitor, or have stopped taking one in the last 14 days, tell your doctor. Medications such as isocarboxazid (Marplan), Linezolid (Zyvox), Methylene blue, phenelzine (Nardil), selegiline (Edelphril, Zelapar or Emsam), and tranylcypromine (Parnate) all can cause interactions with venlafaxine[3] and your doctor will likely advise you against taking it.
  • Discuss with your doctor what prescription and nonprescription medications you will be taking simultaneously with venlafaxine. This includes herbs and vitamins. Others that must be mentioned are blood thinners, amphetamines, painkillers (such as ibuprofen), and medications for migraine management, weight loss, anxiety, pain management, and seizures. You must also mention selective serotonin uptake inhibitors, tricyclic antidepressants, and sleeping pills.
  • If you have glaucoma, venlafaxine is unsuitable, as the drug can increase pressure in the eye and potentially cause loss of sight.
  • If you have ever had an allergic reaction to venlafaxine or any other medication, discuss it with your doctor.
  • If you or a member of your family has ever had a heart problem, discuss with your doctor, as venlafaxine can cause arrhythmia (irregular heartbeat).
  • If you have recently had a heart attack or if you have or had ever had high blood pressure, tell your doctor.
  • If you or a family member has had a history of liver, kidney or thyroid disease, or if you have high cholesterol or seizures, speak with your doctor.
  • If you are having surgery (even dental), you must tell your doctor you are taking venlafaxine.
  • If you have epilepsy or are currently undergoing electroconvulsive treatment, venlafaxine may be unsuitable for you.
  • If you are regent or trying to become pregnant, venlafaxine is probably unsuitable for you.
  • You should not drive or operate heavy machinery until you know how venlafaxine affects you, as it can take up to two weeks before your body adjusts to the drug.

Venlafaxine interactions

Some drugs can interact and have strong reactions to one another. Sometimes this means we are more vulnerable to the side effects of certain drugs, or the intensity of the side effects can be dangerous or even life-threatening. You must never start, stop, change, or up your doses without your doctor’s go-ahead.  

A potentially fatal drug interaction can be caused by taking MAO inhibitors alongside venlafaxine. Generally, MAO inhibitors should not be taken two weeks before or at least seven days after treatment with venlafaxine. MAO inhibitors include isocarboxazid, linezolid, methylene blue, metaxalone, moclobemide, phenelzine, rasagiline, procarbazine, safinamide, tranylcypromine, and selegiline.

Venlafaxine is extremely similar to desvenflaxine. If you are using one already, DO NOT combine with the other.

Aspirin can increase the risk of bleeding when you are taking venlafaxine. However, if your doctor has told you to continue taking a low dose of aspirin to combat the risk of stroke or heart attack, you should continue taking it. But always be sure to discuss this with your doctor or pharmacist first[7].

The risk of serotonin syndrome increases when you take other drug that increase serotonin creation. Recreational drugs such as MDMA or ecstasy, antidepressants or selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine or paroxetine, or serotonin-norepinephrine reuptake inhibitors (SNRIs), namely duloxetine or milnacipran, as well as the herb St. John’s Wort can all cause the risk of serotonin syndrome or toxicity to escalate[4][5].

The use of opioid pain relievers or cough medication should also be discussed with your doctor when taken alongside venlafaxine. These, amongst other medications such as marijuana, drugs to aid sleep or anxiety, muscle relaxants, or antihistamines, all cause drowsiness and should not be taken with venlafaxine without medical advice. 

Check the ingredients of all your current medications/prescriptions or non-prescriptions and discuss with your doctor before embarking on your prescription with venlafaxine. This includes medication for allergies, coughs, or colds. 

It is known that taking venlafaxine can cause false positives for amphetamine use when providing urine samples. Bring your prescription for venlafaxine to the attention of healthcare professionals when undergoing tests[4].

Venlafaxine storage

This drug does not require specific storage but should be kept out of the reach and sight of children.

Do not use venlafaxine past its expiry date, as stated on its packaging.

When wishing to dispose of venlafaxine when it is no longer needed, speak to your pharmacist, drugs should not be disposed of in the ordinary household waste.

What to do if you overdose on venlafaxine

Seek immediate medical attention.

Symptoms of overdose are trouble breathing, drowsiness, rapid heart rate, collapsing, and/or a seizure. However, symptoms may not be limited to just those reactions.


How long does venlafaxine take to work?

It can take 4-6 weeks for venlafaxine to start working. However, many patients feel results in 1-2 weeks.

In the early days of taking the drug, mild headaches, dry mouth, dizziness, and sweating are all commonly reported. This is your body adjusting to the drug, and these side effects should go away in 1-2 weeks.

Will I experience withdrawal symptoms if I stop using venlafaxine?

If you decide you want to stop taking venlafaxine, you should not do so without medical instruction and support, as you may quickly experience withdrawal symptoms from the drug.

This is because venlafaxine’s half-life is extremely short in comparison to other antidepressant medications, meaning your body breaks it down and excretes it very quickly through your urine.

This can mean that for patients taking short-life venlafaxine, their withdrawal symptoms can start the same day as their last dose, and for those taking long-life venlafaxine, their withdrawal symptoms can happen in 1-2 days. For this reason, it is better to wean yourself off the drug in stages. [9]

Commonly reported withdrawal symptoms

  • Anxiety
  • Confusion
  • Diarrhea
  • Nausea
  • Dizziness
  • Electric shock sensations in hands
  • Flu-like symptoms
  • Fatigue
  • Dry mouth
  • Loss of coordination
  • Insomnia 

The best way to stop or minimize withdrawal symptoms when stopping venlafaxine is to reduce dosage over time. The recommended time to taper someone off the medication can vary from two weeks to three months, depending on the dosage taken by the patient.[9].

Is there an alternative to taking venlafaxine?

There are natural serotonin boosters in the world around us. If you decide to take medication, there are lots of avenues to explore as an alternative, and they mostly come down to changes in habits and lifestyle[8].

  • Eat well. Giving your body the balanced nutrition that it needs is known to aid many health conditions. Look up foods that can boost serotonin levels and integrate them into your daily diet.
  • Exercise. When we exercise, our body releases endorphins that trigger the release of serotonin, making us feel happier and more confident.
  • Expose yourself to bright light or sunlight where and when possible. Light therapy is often suggested in the treatment of seasonal depression. Seasonal Adjustment Disorder Lamps (SAD lamps) are a commonly-promoted home-based therapy.  
  • Whilst the effects of meditation still require more research, it is believed that meditation can relieve stress and promote a positive outlook on life.
  1. Venlafaxine. (n.d.). Retrieved November 6, 2022, from
  2. NHS website. (2022, February 15). About venlafaxine.
  3. Venlafaxine: MedlinePlus Drug Information. (n.d.). Retrieved November 6, 2022, from
  4. NCBI – WWW Error Blocked Diagnostic. (n.d.). Retrieved November 6, 2022, from
  5. CKS is only available in the UK. (n.d.). NICE.
  7. National Alliance on Mental Illness. (2020). Venlafaxine (Effexor) | NAMI: National Alliance on Mental Illness.
  8. Bakshi, A., & Tadi, P. (2020). Biochemistry, Serotonin. PubMed; StatPearls Publishing.
  9. Campagne, D. M. (2005). Venlafaxine and Serious Withdrawal Symptoms: Warning to Drivers. Medscape General Medicine, 7(3), 22.
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Nadia Whiston
Author Nadia Whiston Writer

Nadia Whiston is a medical writer with a Master of Arts (MA) degree in English Literature from the University of Bristol and a Bachelor of Arts (BA Hons) degree in English Literature from The University of Manchester.

Published: Nov 22nd 2022, Last edited: Oct 26th 2023

Amy Shelby
Medical Reviewer Amy Shelby M.S. Counseling Psychology

Amy Shelby is a medical reviewer with a B.A. in Psychology from Northwestern and an M.S. in Psychology from Chatham University.

Content reviewed by a medical professional. Last reviewed: Nov 23rd 2022
Medical Reviewer Medical Reviewer:
Amy Shelby
Last reviewed: Nov 23rd 2022 Amy Shelby

M.S. Counseling Psychology