Skip to main content

Warning notification:Warning

Unfortunately, you are using an outdated browser. Please, upgrade your browser to improve your experience with HSE. The list of supported browsers:

  1. Chrome
  2. Edge
  3. FireFox
  4. Opera
  5. Safari


Venlafaxine is an antidepressant used to help people recover from depression.

It's also sometimes used to treat anxiety and panic attacks.

It comes as tablets and capsules. These are only available on prescription.

Venlafaxine is also known by the brand name Efexor XL.

Get emergency help 

You might need to get emergency help if you:

  • take too much venlafaxine
  • have a serious allergic reaction
  • get serious side effects

If you take too much

Emergency action required: Call 112 or 999 or go to an emergency department (ED) if you:

  • take too much venlafaxine, even if you feel well

Get someone else to drive you or call 999 or 112 for an ambulance.

Take the venlafaxine packet or the leaflet inside it, and any remaining medicine with you.

If you take too much venlafaxine, you may:

  • feel sleepy
  • get sick (vomiting)
  • have a racing heart
  • have seizures
  • get blurred vision

Serious side effects

Serious side effects from taking venlafaxine are not common.

Emergency action required: Call 999 or 112 or go to an emergency department (ED) immediately if you have:

  • chest pain or pressure, shortness of breath, or a fast or irregular heart beat
  • severe dizziness or passing out
  • any bleeding that is very bad or that you cannot stop such as cuts or nose bleeds that don't stop within 10 minutes

Urgent advice: Contact your GP urgently if you have any of the following symptoms:

  • constant headaches
  • long-lasting confusion or weakness
  • frequent muscle cramps
  • feelings of euphoria, excessive enthusiasm or excitement
  • a feeling of restlessness that means you can't sit or stand still
  • unexplained muscle pain or weakness
  • yellow skin or the whites of your eyes turn yellow
  • any changes in your eyesight, like blurred vision or dilated pupils
  • vomiting blood or dark vomit, coughing up blood, blood in your pee, black or red poo
  • bleeding from the gums or bruises that appear without a reason or that get bigger
  • thoughts about harming yourself or ending your life

Non-urgent advice: Talk to your GP if you have:

  • weight gain or weight loss without trying
  • changes in your periods such as heavy bleeding, spotting, or bleeding between periods

Serious allergic reaction

Emergency action required: Call 999 or 112 or go to an emergency department (ED) immediately if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

Check if you can take venlafaxine

Venlafaxine can be taken by adults.

Check with your GP before you start taking venlafaxine if you are:

  • taking other medicines
  • trying to get pregnant, pregnant or breastfeeding
  • have had an allergic reaction to any medicines in the past
  • have a heart problem, glaucoma or epilepsy
  • are having electroconvulsive treatment - venlafaxine may increase your risk of having a seizure
  • are taking any herbal remedies, vitamins or supplements

Pregnancy and venlafaxine

Talk to your GP before taking venlafaxine if you:

  • are pregnant
  • think you may be pregnant
  • are trying to get pregnant

If you become pregnant while taking venlafaxine, do not stop taking the medicine before talking to your GP.

Your GP may advice you to take venlafaxine during pregnancy if you need it to remain well. They can explain the risks and the benefits. They will help you decide the best treatment for you and your baby.

Make sure your midwife and any doctors treating you throughout your pregnancy knows you taking venlafaxine. 

Risks to newborn babies

Venlafaxine may increase the risk of:

  • persistent pulmonary hypertension (PPHN) in your newborn baby - this is a serious condition
  • heavy vaginal bleeding after birth

Emergency action required: Contact your midwife or GP urgently if your newborn is:

  • breathing faster
  • blue in colour

These symptoms usually begin in the first 24 hours after birth.

If your baby is not feeding properly and you were taking venlafaxine during your pregnancy, contact your GP or midwife. 

Breastfeeding and venlafaxine

Talk to your GP if you are breastfeeding. Do this before taking venlafaxine.

Venlafaxine passes into breastmilk. This may affect your baby.

Your GP will advise you if you should take a different medicine or stop breastfeeding.

When you start taking venlafaxine

Your symptoms might improve after a week of taking venlafaxine.

You usually won't feel the full benefits for up to 6 weeks.

Driving, cycling and operating machinery

Some people cannot concentrate properly while they're taking venlafaxine. 

It might be best to stop driving, cycling and operating complex machinery for the first few days of treatment until you know how this medicine makes you feel.

Check your blood sugar if you have diabetes

Check your blood sugar more for the first few weeks of taking venlafaxine if you have diabetes.

Your diabetes treatment might need to be adjusted depending on your blood sugar levels.

How and when to take venlafaxine

Take venlafaxine as recommended by your GP. Check with your GP or pharmacist if you are not sure.

If you're prescribed capsules, you must swallow them whole with water. Do not crush, cut, open, dissolve or chew the capsule.

Try take the medicine at the same time each day, either in the morning or in the evening. Take it with food so it does not make you feel sick.

Your GP might prescribe a lower dose if you have problems with your liver or kidneys.

Avoid drinking alcohol while you're taking venlafaxine.

If you forget to take it

Do not worry if you occasionally forget to take a dose. Take your next dose at the usual time.

Never take 2 doses at the same time to make up for a forgotten one.

Use an alarm to remind you if you often forget to take doses. 

How long you'll need to take venlafaxine

When you're feeling better, it's likely that you will continue to take venlafaxine for several more months. 

You’ll usually take antidepressants for 6 months to 1 year after you no longer feel depressed.

Stopping before that time can make depression come back.

Side effects

Venlafaxine can cause side effects. But many people have no side effects or only minor ones. 

Common side effects include:

  • feeling sick
  • headaches
  • sweating
  • dry mouth

These are usually mild and go away after a couple of weeks. 

Your GP will usually recommend reducing your dose gradually to help control extra side effects if they take you off venlafaxine.

Tell your GP or pharmacist if side effects bother you or do not go away.

See the patient information leaflet that comes with your medicine for a full list of side effects.

Non-urgent advice: Find your patient information leaflet

Your patient information leaflet is the leaflet that comes with your medicine. You can find a digital version of the leaflet online.

Report side effects

You can report any suspected side effects to the the Health Products Regulatory Authority (HPRA): report an issue -

Taking venlafaxine with other medicines

Venlafaxine can interfere with other medicines and increase the chance of side effects.

Tell a GP or pharmacist if you're taking other medicines before you start venlafaxine, particularly any medicines:

  • that affect your heartbeat
  • for depression
  • used to treat pain
  • used to treat coughing, such as cough syrup

Do not take St John’s wort

Do not take the herbal remedy for depression, St John's wort, while you are taking venlafaxine. This will increase your risk of potentially life-threatening side effects, such as serotonin syndrome.

Serotonin syndrome

Serotonin syndrome is a potentially life-threatening condition. It can develop if you take venlafaxine, but particularly if you take it with other medicines or herbal remedies.

Urgent advice: Go to your nearest emergency department (ED) or phone a GP if:

you have 1 or a combination of the following:

  • restlessness
  • hallucinations
  • loss of coordination
  • increased heart beat
  • increased body temperature
  • rapid changes in blood pressure
  • overactive reflexes
  • diarrhoea
  • passing out
  • feeling sick (nausea) or being sick (vomiting)

In severe case, serotonin syndrome can seem similar to Neuroleptic Malignant Syndrome (NMS).

Symptoms of NMS may include a combination of

  • high temperature of 38 degrees Celsius or above
  • increased heart beat
  • sweating
  • severe muscle stiffness
  • confusion

Fact check

This content was fact checked by a pharmacist, a GP, the National Medication Safety Programme (Safermeds) and the Health Products Regulatory Authority (HPRA).

Page last reviewed: 24 September 2021
Next review due: 24 September 2024

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.