a teacher sits beside a student to help her as she answer her exam

Your guide to medication Venlafaxine

Venlafaxine is an SNRI antidepressant that is commonly used to treat anxiety and depression.

Medication name: Venlafaxine ("ven-la-FAX-een")
Brand name: Efexor XL¬ģ ("e-FEX-or")
Medication type: Serotonin and noradrenaline re-uptake inhibitor (SNRI)

Ways to take venlafaxine
Tablets: 37.5mg and 75mg strengths
Modified-release (long-acting) tablets: (37.5mg, 75mg, 150mg and 225mg strengths)
Modified-release (long-acting) capsules: (75mg and 150mg strengths)

What can it be used for?
If you are 18 or over, the doctor can prescribe venlafaxine for you as a licensed medicine for depression, social anxiety disorder, generalised anxiety disorder, and panic disorders.

There is less research about its use and effectiveness in young people under 18. Even so, specialists might prescribe it 'off-label' if they believe it is the best medicine for you.

Read our guide to depression

About venlafaxine

How venlafaxine works

Venlafaxine is a type of antidepressant known as a serotonin-noradrenaline reuptake inhibitor (SNRI).

(N.B. Noradrenaline is sometimes known as norepinephrine.)

Research suggests that depression is more likely to occur when the brain doesn‚Äôt have enough of the chemicals¬†serotonin¬†(also called ‚Äė5HT‚Äô) and¬†noradrenaline.

Nerve endings in the brain release these chemicals and take them back up again after they have targeted their receptors in what is known as a recycling process.

Serotonin and noradrenaline reuptake inhibitors (SNRIs) ‚Äď like venlafaxine - work by blocking recycling of released serotonin and noradrenaline back into the nerve endings.

This increases the amount of serotonin and noradrenaline, which helps treat the symptoms.

Venlafaxine also works on blocking the recycling of dopamine, adding further to its antidepressant effect.

It is worth noting that as the dose of venlafaxine is increased, it becomes more effective at blocking noradrenaline reuptake. However, its effect on serotonin and dopamine stays much the same.

This means that some people may not get the full benefit of venlafaxine until they are on a higher dose.

Venlafaxine and everyday life

Frequently asked questions

Antidepressants like venlafaxine can start to work on depression within the first two weeks of treatment. The extent of any improvements you feel should continue to increase over the following few weeks.

It may take four weeks or longer for you to get the full effect.

For anxiety, antidepressants like venlafaxine can take slightly longer to work. For some people, anxiety briefly increases at the start of treatment, but it does decrease with continued treatment.

To get the best effect, you need to take your venlafaxine every day and give it a chance to work for you.

Your doctor will start with a low dose, which they will increase slowly to a dose that is effective for you. This may take several days or weeks.

Venlafaxine can give you a dry mouth, and can increase your risk of developing tooth decay.

Make sure you brush your teeth well and have regular check-ups while you are on venlafaxine.

Venlafaxine can also cause weight gain or weight loss.

There is not usually a lot of weight gain, but it is very difficult to know how it will affect each person who takes it.

Do not take venlafaxine at the same time as weight-loss products.

Talk to your doctor about this if it worries you.

You may want to let your family and friends know you are taking venlafaxine so they can support you and help you look out for side effects.

For guidance on this, check out our page on getting support with your medication.

You can feel drowsy in the first few days of taking venlafaxine. This should get better after the first week or two.

You could also, strangely, get insomnia (difficulty getting to sleep), and disturbing dreams or nightmares.

If you feel like a zombie, and you’ve been taking it for more than a month, you should go back to the doctor and see what else you could do.

Alcohol

You can continue to drink alcohol while taking venlafaxine, but having the two together might make you very sleepy and unsteady on your feet.

So, during the first few days, it might be best to stop drinking alcohol until you see how the medicine affects you, or until the side effects pass.

If you want to drink alcohol, remember that you might be very sleepy and make sure you can get home safely.

Drinking alcohol every day, or in large amounts, can make your symptoms worse and the venlafaxine will not get the best chance to act.

Street drugs

Cannabis can make drowsiness worse with venlafaxine.

Cannabis and other drugs may have their own side effects on your mental health, like anxiety or psychosis. For more information, have a look at our drugs and alcohol page.

Methadone and heroin can make drowsiness worse with venlafaxine.

Taking venlafaxine with cocaine, ecstasy or amfetamines could bring on serotonin syndrome. You could get a high temperature/fever, agitation, confusion, trembling or weird muscle movements. You need to go to hospital if this happens. Tell the doctor everything that you have taken.

There are many other street drugs, but we don’t know what effect taking them with venlafaxine will have.

Venlafaxine does not mix well with some other medicines and drugs.

Do not take venlafaxine if you are taking or have taken MAOIs (like isocarboxazid, moclobemide, phenelzine or tranylcypromine) in the last 14 days. You must wait until 14 clear days have passed before you can take venlafaxine.

Tell your doctor and pharmacist before you take venlafaxine if you are taking any other medicines (including herbal medicines or anything bought at the pharmacy).

The tablets may not be suitable for you if you have problems eating some sugars or dairy (milk-based) foods, as they contain lactose.

Let your pharmacist know if you have any food allergies or intolerances, and always check with them if you’re concerned about any of the ingredients in your medication.

Taking venlafaxine may make you feel sleepy, dizzy and restless, and could affect your eyesight when you start taking it.

This could affect you if you drive a car, ride a bike, or do anything else that needs a lot of focus. It might be best to stop doing these things for the first few days, until you know how it affects you.

Do not worry - most people drive as normal while taking venlafaxine.

Pregnancy

When deciding whether to take venlafaxine during pregnancy it is important to weigh up how necessary venlafaxine is to your health against the possible risks to you or your baby, some of which will depend on how many weeks pregnant you are.

There does not appear to be a link with an increased risk of malformations or having a baby born early.

It is less clear if there might be a small increase in the risk of miscarriage or heart defects.

If venlafaxine is taken after 20 weeks of pregnancy, there is¬†in theory¬†a risk of something called ‚Äúpersistent pulmonary hypertension in the newborn‚ÄĚ (or PPHN.) This can make the baby breathe faster and look a bit blue in colour. There is not enough research to be able to tell whether this happens with venlafaxine or not. If it does occur, it can be treated by your medical team much better if they know about it in advance, so let your midwife and doctor know that you take venlafaxine.

Post-natal

If you take venlafaxine in the weeks before delivery, your baby may have discontinuation symptoms, including:

  • irritability
  • excessive crying
  • shivering
  • problems with eating or sleeping

These are usually mild and go away in a few days without treatment.

Breastfeeding

Venlafaxine is passed to the baby in small amounts through breast milk. While this can help with any discontinuation effects, other side effects have been seen in breastfed babies.

Remember that it is important for you to remain well while you are bonding with and looking after your baby. For this reason, it may be best to take medicine for your mental health when breastfeeding.

You may also need to consider bottle-feeding with formula milk if there are any problems with breastfeeding while taking medicines.

Talk to your doctor or midwife about your feeding options.

Make sure that your doctor, nurse, or health visitor checks your baby for any side effects. These can include:

  • being extra sleepy
  • having colic
  • feeding problems
  • poor weight-gain

If your baby was premature or has health problems, then you will need to be extra careful about taking medicines while breastfeeding. It may be best not to breastfeed if this is the case, however you should discuss this with your doctor.

Sex

Venlafaxine can have side effects that might affect your sex life, including:

  • problems getting an erection (getting hard) and ejaculating (coming)
  • a painful erection that lasts for a long time (priapism) - if you do get this, you need to get medical help straight away
  • problems with your period
  • decrease in libido (lower sex-drive)

These effects should pass after the first couple of weeks. If they do not, and this is a problem for you, go back to the doctor and see what else you could try.

If it works for you, venlafaxine may have a positive effect on your sex life as your symptoms settle, and you can concentrate on your relationships.

Fertility

There is nothing to suggest that venlafaxine causes any problems with fertility.

Venlafaxine is not a banned substance in sport.

Taking venlafaxine may affect your ability to do things like riding a bike, competitive gymnastics, or anything else that needs a lot of focus.

You may find it difficult to sit or stand still easily at first.

It may also affect your eyesight.

It might produce ringing in your ears, or vertigo.

It might be best to stop such sports for the first few days, until you know how it affects you.

Do not worry - most people play sports as normal while taking venlafaxine.

Try not to take venlafaxine for the first time just before your exams.

Venlafaxine can make you feel restless in the first few weeks that you take it, and you may not be able to sit or stand still easily.

It can also disturb your sleep, and your eyesight.

You should talk to your doctor about any future exams if you are starting venlafaxine.

You might decide together to delay starting it until you have done them.

If they are more than a month away, however, you might find that it is better to start venlafaxine to improve your motivation to study.

Do not worry - most people take exams as normal while taking venlafaxine.

Your doctor should know

  • You need to talk to your doctor or¬†pharmacist¬†before starting treatment with venlafaxine if you have any of the following:

    • eye problems, such as glaucoma (increased pressure in the eye)
    • a history of high blood pressure
    • a history of heart problems
    • a history of seizures (fits)
    • a history of low sodium levels in your blood (hyponatraemia)
    • a tendency to develop bruises or a tendency to bleed easily (history of bleeding disorders), or if you are taking other medicines that may increase the risk of bleeding like warfarin (used to prevent blood clots)
    • a history of, or a family history of, bipolar disorder or¬†mania¬†(feeling over-excited or euphoric)
    • a history of aggressive behaviour
    • a history of¬†thoughts of harming yourself or taking your own life.

Uses, warnings, safety and side effects

Taking venlafaxine

How long will I need to take venlafaxine for?

You will need to take venlafaxine for several months after you feel better, otherwise your symptoms can come back. For depression this might be for six months, but for other conditions such as generalised anxiety disorder it might be up to 18 months.

If your illness has come back, then you might be advised to keep taking venlafaxine for longer than this.

If you stop taking the venlafaxine too soon, there is more chance that your symptoms will come back.

Discuss with your doctor how long you should take venlafaxine for.

If you have bipolar disorder, it is likely that the doctor will advise for the venlafaxine to be stopped sooner. This is because, in bipolar disorder, there is a risk of your mood becoming too high if an antidepressant is used for too long.

Your dose will need to be reduced gradually to reduce the chance of withdrawal effects when it is stopped (unless you are already on the lowest dose).

You should only take venlafaxine as agreed with your doctor

You will get most benefit from your venlafaxine if you take it every day at the dose prescribed by your doctor.

Make sure that you know your dose. If it is not written on the label, check with your pharmacist or doctor.

You will usually take it once a day (if you take the modified-release or prolonged-release tablets or capsules) or twice a day (if it is the plain tablets).

You will usually start with a low dose that your doctor will gradually increase to a dose that is effective for you. This may take several weeks.

Choose a time of the day to take venlafaxine that you can always remember. As venlafaxine should be taken with food, this could be a mealtime or when you have a snack.

Take venlafaxine with food.

Swallow the tablet whole with a glass of water - it tastes bitter if you chew it.

If you find it difficult to take it more than once a day, ask your doctor about the long-acting tablets or capsules because they only need to be taken once a day.

Swallow the long-acting tablets or capsules whole with a drink of water - they are specially made to release the medicine over a few hours into your body and should not be broken, crushed or chewed.

Some parts of the long-acting capsules do not get absorbed into the body and pass straight through. You might see small white balls or granules in your poo. This is not a problem.

What if I miss a dose?

If you remember later during the day, take it as soon as possible. However, if this is more than six hours after the dose should be taken, it is usually better to miss the dose and just start again at the next dose.

If you forget to take it by the next dose, just start again with the next dose.

Do not take a double dose.

What will happen if I forget to take my venlafaxine?

If you forget to take your tablets for a few days, you may start getting your old symptoms back, or get withdrawal symptoms (feeling dizzy or shaky, sleep problems [including difficulty sleeping and intense dreams], feeling irritable or anxious, feeling or being sick, and headaches). If this happens you should talk to your doctor about it.

Stopping the use of venlafaxine

Stopping this medicine quickly, or reducing the dose too much at once, may cause uncomfortable symptoms.

You can stop taking it safely by stepping down the dose gradually with your doctor’s help.

Once you start taking venlafaxine, the brain adjusts to having a new level of serotonin and noradrenaline around. If you stop taking venlafaxine suddenly, you could get some withdrawal symptoms.

Venlafaxine is not addictive, but you may get uncomfortable withdrawal symptoms if you stop taking it suddenly, as your body begins to miss it. It is better to agree stopping with a doctor who will reduce your dose gradually over several weeks.

Some of the withdrawal symptoms you might get include:

  • dizziness, feeling light-headed or having headaches
  • tingling feelings like pins and needles or ‚Äėelectric shock‚Äô feelings
  • sleep disturbances (vivid dreams, nightmares, not being able to sleep)
  • feeling anxious, nervous, agitated or confused
  • feeling sick or being sick
  • diarrhoea (loose poo)
  • shaking
  • feeling tired and weak
  • dry mouth and losing your appetite
  • sweating
  • ringing in the ears
  • feeling like you have got flu (muscle weakness and fever)

These symptoms should stop after one to two weeks for most people, but some people can get them for longer.

Most people get mild symptoms, but for some people they can be very intense.

Go and speak to your doctor if you have missed a few doses or have decided to stop taking your medication.

When you agree with your doctor to stop the venlafaxine, it is usually best to come off slowly over a few weeks. This will lower your risk of getting withdrawal symptoms.

Warnings and safety

Safety headlines

If you have taken more venlafaxine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately ‚Ästeven if you do not feel any different.

While taking venlafaxine, some people may think about hurting themselves or taking their own lives. Go straight to hospital with your tablets if you have any of these thoughts.

Venlafaxine can also cause other rare, but serious side effects: allergic reactions (difficulty breathing, swelling of your face or throat, itching skin lumps, severe rash), unexplained muscle pain and tenderness, chest tightness, difficulty breathing, or serotonin syndrome (symptoms of this include a high fever, agitation, confusion, trembling, or weird movements of your muscles). Go to a hospital if you get any of these symptoms and take your medicine with you.

Do not take venlafaxine if you have taken a monoamine oxidase inhibitor antidepressant (MAOI) like moclobemide, phenelzine, isocarboxazid or tranylcypromine in the last 14 days.

Stopping venlafaxine suddenly can cause serious side effects. Go to your doctor if you want to stop, or if you are having these effects.

Venlafaxine is not addictive, but stopping it suddenly can cause problems such as: feeling dizzy or shaky, sleep problems (including difficulty sleeping and intense dreams), feeling irritable or anxious, feeling or being sick, and headaches. Go to your doctor if you want to stop, or if you are having these effects.

You might feel sleepy or restless, and may not be able to see properly, in the first few days after taking venlafaxine. Do not drive a car, ride a bike or operate machines until you see how this affects you.

Venlafaxine may affect the developing baby during pregnancy. If you are trying for a baby or become pregnant while taking venlafaxine, you should speak with your doctor as soon as possible to discuss options and alternatives.  

When to go to the hospital

If you have taken more venlafaxine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately ‚Ästeven if you do not feel any different. Go to A&E. Take your medicine with you to show to the doctors. Tell them how much you have taken. Get a friend to go with you, if you can, just in case you feel ill on the way.

You might get any of the following signs:

  • fast heartbeat
  • feeling less alert (from sleepiness to coma)
  • blurred eyesight
  • seizures (fits)
  • being sick
  • high fever, agitation, confusion, trembling, or weird movements of your muscles (these could be signs of¬†serotonin syndrome)

While taking venlafaxine, some people may think about hurting themselves or taking their own lives. This is more common at the start of treatment than later. This can happen to anyone but is more likely to happen if you are less than 25 years old.

You must to straight to hospital if you have thoughts of hurting yourself or taking your own life. Take your medicines with you and tell the doctor that you are taking venlafaxine.

Go to a doctor or hospital straight away if you get any of the following symptoms:

  • thoughts of harming yourself or taking your own life
  • chest tightness, wheezing, trouble swallowing or breathing
  • swelling of the face, throat, hands, or feet
  • feeling nervous or anxious, dizziness, throbbing sensations, sudden reddening of the skin and/or a warm feeling
  • a bad rash, itching, or ‚Äėhives‚Äô (raised patches of red or pale skin that often itch)
  • any signs and symptoms of¬†serotonin syndrome¬†which may include restlessness, hallucinations, loss of co-ordination, fast heartbeat, increased body temperature, overactive reflexes, diarrhoea, coma, feeling or being sick
  • a painful erection that lasts for a long time (priapism)
  • seizures (fits)

When to see your doctor

Tell your doctor straight away if you develop any of the following:

  • coughing, wheezing, shortness of breath and a high temperature
  • black (tarry) poo, or blood in your poo
  • your skin or the whites of your eyes going yellow, with itching or dark urine (wee), which may be symptoms of hepatitis (a problem with your liver)
  • heart problems, such as fast or uneven heartbeat and higher blood pressure
  • eye problems, such as blurred eyesight, or your pupils (black centre of the eye) getting bigger
  • nerve problems, such as dizziness, pins and needles, movement problems, or fits
  • mental health problems, such as hyperactivity and euphoria (feeling unusually overexcited)
  • if you cut or injure yourself, and the bleeding takes a long time to stop
  • a severe skin rash that causes blistering, including your mouth and tongue. These may be signs of a condition known as Stevens Johnson Syndrome, or toxic epidermal necrolysis (TEN). Your doctor will stop your treatment in these cases
  • allergic reaction or allergy, which may include symptoms such as an itchy skin rash, breathing problems, wheezing, swollen eyelids, face or lips
  • rhythmic movements of your muscles that you cannot control, especially in your tongue and mouth

Side effects

Side effects

Like all medicines, venlafaxine can cause side effects, which can be serious.

In clinical trials, young people aged under 25 were more likely than adults to get the following side effects from SSRI or SNRI medicines:

  • thoughts of self-harm and/or taking their own lives
  • self-harm
  • hostile or aggressive behaviour

Not everyone will experience side effects with venlafaxine. If you do experience side effects, some of them should disappear or get better within a few days or weeks.

Very common side effects (affecting more than one in ten people) include:

  • feeling sick
  • feeling dizzy
  • headache
  • dry mouth
  • sweating (including night sweats)
  • constipation (difficulty pooing)

Common side effects (affecting up to one in ten people) include:

  • feeling less hungry
  • confusion, feeling nervous, feeling separated (or detached) from yourself
  • difficulty having an orgasm, not wanting to have sex or, for people who have a penis, difficulty in getting an erection or ejaculating (coming)
  • feeling tired, feeling weak, having difficulty sleeping, or unusual dreams
  • shaking, having pins and needles, increased muscle tone
  • effects on eyesight like blurred vision, dilated pupils (centre of the eye gets bigger), difficulty of changing eye focus from far to near objects
  • tinnitus (ringing in the ears)
  • palpitations, increase in blood pressure, hot flushing, sweating or feeling chills
  • yawning a lot
  • vomiting (being sick)
  • diarrhoea (loose poo)
  • wanting to wee more often, or having difficulty going for a wee
  • problems with periods such as more bleeding or irregular bleeding
  • increased blood cholesterol (seen in blood tests)

If you are experiencing a problem that might be a side effect, but that is not listed here, please look at the patient information leaflet that was in the medicine packet, or speak to your pharmacist or doctor. If you think you have a side effect that has not got better within a few days go back to your doctor.

Taking venlafaxine

How long will I need to take venlafaxine for?

You will need to take venlafaxine for several months after you feel better, otherwise your symptoms can come back. For depression this might be for six months, but for other conditions such as generalised anxiety disorder it might be up to 18 months.

If your illness has come back, then you might be advised to keep taking venlafaxine for longer than this.

If you stop taking the venlafaxine too soon, there is more chance that your symptoms will come back.

Discuss with your doctor how long you should take venlafaxine for.

If you have bipolar disorder, it is likely that the doctor will advise for the venlafaxine to be stopped sooner. This is because, in bipolar disorder, there is a risk of your mood becoming too high if an antidepressant is used for too long.

Your dose will need to be reduced gradually to reduce the chance of withdrawal effects when it is stopped (unless you are already on the lowest dose).

You should only take venlafaxine as agreed with your doctor

You will get most benefit from your venlafaxine if you take it every day at the dose prescribed by your doctor.

Make sure that you know your dose. If it is not written on the label, check with your pharmacist or doctor.

You will usually take it once a day (if you take the modified-release or prolonged-release tablets or capsules) or twice a day (if it is the plain tablets).

You will usually start with a low dose that your doctor will gradually increase to a dose that is effective for you. This may take several weeks.

Choose a time of the day to take venlafaxine that you can always remember. As venlafaxine should be taken with food, this could be a mealtime or when you have a snack.

Take venlafaxine with food.

Swallow the tablet whole with a glass of water - it tastes bitter if you chew it.

If you find it difficult to take it more than once a day, ask your doctor about the long-acting tablets or capsules because they only need to be taken once a day.

Swallow the long-acting tablets or capsules whole with a drink of water - they are specially made to release the medicine over a few hours into your body and should not be broken, crushed or chewed.

Some parts of the long-acting capsules do not get absorbed into the body and pass straight through. You might see small white balls or granules in your poo. This is not a problem.

What if I miss a dose?

If you remember later during the day, take it as soon as possible. However, if this is more than six hours after the dose should be taken, it is usually better to miss the dose and just start again at the next dose.

If you forget to take it by the next dose, just start again with the next dose.

Do not take a double dose.

What will happen if I forget to take my venlafaxine?

If you forget to take your tablets for a few days, you may start getting your old symptoms back, or get withdrawal symptoms (feeling dizzy or shaky, sleep problems [including difficulty sleeping and intense dreams], feeling irritable or anxious, feeling or being sick, and headaches). If this happens you should talk to your doctor about it.

Stopping the use of venlafaxine

Stopping this medicine quickly, or reducing the dose too much at once, may cause uncomfortable symptoms.

You can stop taking it safely by stepping down the dose gradually with your doctor’s help.

Once you start taking venlafaxine, the brain adjusts to having a new level of serotonin and noradrenaline around. If you stop taking venlafaxine suddenly, you could get some withdrawal symptoms.

Venlafaxine is not addictive, but you may get uncomfortable withdrawal symptoms if you stop taking it suddenly, as your body begins to miss it. It is better to agree stopping with a doctor who will reduce your dose gradually over several weeks.

Some of the withdrawal symptoms you might get include:

  • dizziness, feeling light-headed or having headaches
  • tingling feelings like pins and needles or ‚Äėelectric shock‚Äô feelings
  • sleep disturbances (vivid dreams, nightmares, not being able to sleep)
  • feeling anxious, nervous, agitated or confused
  • feeling sick or being sick
  • diarrhoea (loose poo)
  • shaking
  • feeling tired and weak
  • dry mouth and losing your appetite
  • sweating
  • ringing in the ears
  • feeling like you have got flu (muscle weakness and fever)

These symptoms should stop after one to two weeks for most people, but some people can get them for longer.

Most people get mild symptoms, but for some people they can be very intense.

Go and speak to your doctor if you have missed a few doses or have decided to stop taking your medication.

When you agree with your doctor to stop the venlafaxine, it is usually best to come off slowly over a few weeks. This will lower your risk of getting withdrawal symptoms.

Warnings and safety

Safety headlines

If you have taken more venlafaxine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately ‚Ästeven if you do not feel any different.

While taking venlafaxine, some people may think about hurting themselves or taking their own lives. Go straight to hospital with your tablets if you have any of these thoughts.

Venlafaxine can also cause other rare, but serious side effects: allergic reactions (difficulty breathing, swelling of your face or throat, itching skin lumps, severe rash), unexplained muscle pain and tenderness, chest tightness, difficulty breathing, or serotonin syndrome (symptoms of this include a high fever, agitation, confusion, trembling, or weird movements of your muscles). Go to a hospital if you get any of these symptoms and take your medicine with you.

Do not take venlafaxine if you have taken a monoamine oxidase inhibitor antidepressant (MAOI) like moclobemide, phenelzine, isocarboxazid or tranylcypromine in the last 14 days.

Stopping venlafaxine suddenly can cause serious side effects. Go to your doctor if you want to stop, or if you are having these effects.

Venlafaxine is not addictive, but stopping it suddenly can cause problems such as: feeling dizzy or shaky, sleep problems (including difficulty sleeping and intense dreams), feeling irritable or anxious, feeling or being sick, and headaches. Go to your doctor if you want to stop, or if you are having these effects.

You might feel sleepy or restless, and may not be able to see properly, in the first few days after taking venlafaxine. Do not drive a car, ride a bike or operate machines until you see how this affects you.

Venlafaxine may affect the developing baby during pregnancy. If you are trying for a baby or become pregnant while taking venlafaxine, you should speak with your doctor as soon as possible to discuss options and alternatives.  

When to go to the hospital

If you have taken more venlafaxine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately ‚Ästeven if you do not feel any different. Go to A&E. Take your medicine with you to show to the doctors. Tell them how much you have taken. Get a friend to go with you, if you can, just in case you feel ill on the way.

You might get any of the following signs:

  • fast heartbeat
  • feeling less alert (from sleepiness to coma)
  • blurred eyesight
  • seizures (fits)
  • being sick
  • high fever, agitation, confusion, trembling, or weird movements of your muscles (these could be signs of¬†serotonin syndrome)

While taking venlafaxine, some people may think about hurting themselves or taking their own lives. This is more common at the start of treatment than later. This can happen to anyone but is more likely to happen if you are less than 25 years old.

You must to straight to hospital if you have thoughts of hurting yourself or taking your own life. Take your medicines with you and tell the doctor that you are taking venlafaxine.

Go to a doctor or hospital straight away if you get any of the following symptoms:

  • thoughts of harming yourself or taking your own life
  • chest tightness, wheezing, trouble swallowing or breathing
  • swelling of the face, throat, hands, or feet
  • feeling nervous or anxious, dizziness, throbbing sensations, sudden reddening of the skin and/or a warm feeling
  • a bad rash, itching, or ‚Äėhives‚Äô (raised patches of red or pale skin that often itch)
  • any signs and symptoms of¬†serotonin syndrome¬†which may include restlessness, hallucinations, loss of co-ordination, fast heartbeat, increased body temperature, overactive reflexes, diarrhoea, coma, feeling or being sick
  • a painful erection that lasts for a long time (priapism)
  • seizures (fits)

When to see your doctor

Tell your doctor straight away if you develop any of the following:

  • coughing, wheezing, shortness of breath and a high temperature
  • black (tarry) poo, or blood in your poo
  • your skin or the whites of your eyes going yellow, with itching or dark urine (wee), which may be symptoms of hepatitis (a problem with your liver)
  • heart problems, such as fast or uneven heartbeat and higher blood pressure
  • eye problems, such as blurred eyesight, or your pupils (black centre of the eye) getting bigger
  • nerve problems, such as dizziness, pins and needles, movement problems, or fits
  • mental health problems, such as hyperactivity and euphoria (feeling unusually overexcited)
  • if you cut or injure yourself, and the bleeding takes a long time to stop
  • a severe skin rash that causes blistering, including your mouth and tongue. These may be signs of a condition known as Stevens Johnson Syndrome, or toxic epidermal necrolysis (TEN). Your doctor will stop your treatment in these cases
  • allergic reaction or allergy, which may include symptoms such as an itchy skin rash, breathing problems, wheezing, swollen eyelids, face or lips
  • rhythmic movements of your muscles that you cannot control, especially in your tongue and mouth

Side effects

Side effects

Like all medicines, venlafaxine can cause side effects, which can be serious.

In clinical trials, young people aged under 25 were more likely than adults to get the following side effects from SSRI or SNRI medicines:

  • thoughts of self-harm and/or taking their own lives
  • self-harm
  • hostile or aggressive behaviour

Not everyone will experience side effects with venlafaxine. If you do experience side effects, some of them should disappear or get better within a few days or weeks.

Very common side effects (affecting more than one in ten people) include:

  • feeling sick
  • feeling dizzy
  • headache
  • dry mouth
  • sweating (including night sweats)
  • constipation (difficulty pooing)

Common side effects (affecting up to one in ten people) include:

  • feeling less hungry
  • confusion, feeling nervous, feeling separated (or detached) from yourself
  • difficulty having an orgasm, not wanting to have sex or, for people who have a penis, difficulty in getting an erection or ejaculating (coming)
  • feeling tired, feeling weak, having difficulty sleeping, or unusual dreams
  • shaking, having pins and needles, increased muscle tone
  • effects on eyesight like blurred vision, dilated pupils (centre of the eye gets bigger), difficulty of changing eye focus from far to near objects
  • tinnitus (ringing in the ears)
  • palpitations, increase in blood pressure, hot flushing, sweating or feeling chills
  • yawning a lot
  • vomiting (being sick)
  • diarrhoea (loose poo)
  • wanting to wee more often, or having difficulty going for a wee
  • problems with periods such as more bleeding or irregular bleeding
  • increased blood cholesterol (seen in blood tests)

If you are experiencing a problem that might be a side effect, but that is not listed here, please look at the patient information leaflet that was in the medicine packet, or speak to your pharmacist or doctor. If you think you have a side effect that has not got better within a few days go back to your doctor.

About this information

The information on this page was reviewed by the College of Mental Health Pharmacy in March 2020.

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