Venlafaxine is an antidepressant. It helps you recover from depression.
Venlafaxine is only available on prescription.
It comes as tablets and capsules.
It is also known by the brand names Efexor XL, Vedixal, Venex, Venlablue, Venlofex and Venlafex.
Uses of venlafaxine
Venlafaxine is a serotonin and noradrenaline reuptake inhibitor (SNRI). It is thought to work by increasing levels of mood-enhancing chemicals in your brain called serotonin and noradrenaline.
Venlafaxine is usually prescribed to treat depression.
Your GP might also recommend it for:
- anxiety
- panic attacks
Check if you can take venlafaxine
Venlafaxine can be taken by adults. But it is not suitable for everyone.
Before you start taking venlafaxine tell your GP if you:
- are taking other medicines
- are trying to get pregnant, are pregnant or breastfeeding
- had an allergic reaction to any medicines in the past
- have a heart problem, glaucoma or epilepsy
- are having electroconvulsive treatment (ECT) - venlafaxine may increase your risk of having a seizure
- are taking any herbal remedies, vitamins or supplements
Pregnancy and venlafaxine
If you become pregnant while taking venlafaxine, do not stop taking the medicine before talking to your GP.
Your GP may recommend you take venlafaxine during pregnancy.
Your GP will:
- explain the risks and benefits of taking the medicine
- help you decide the best treatment for you and your baby
Tell your midwife and any doctors treating you during pregnancy that you take venlafaxine.
It’s important that your mental health is treated since this can impact on your and your baby’s wellbeing. Depression and anxiety can sometimes get worse during pregnancy and after your baby has been born.
Risks to newborn babies
Venlafaxine may increase the risk of:
- a serious breathing problem in your baby called persistent pulmonary hypertension of the newborn
- heavy vaginal bleeding after birth
Emergency action required: Contact your midwife or GP urgently if your newborn:
- is breathing faster
- looks blue
These symptoms may happen in the first 24 hours after birth.
Non-urgent advice: Contact your GP or midwife if
you were taking venlafaxine during pregnancy and:
- your baby is not feeding well
Breastfeeding and venlafaxine
Venlafaxine passes into breastmilk. This may affect your baby.
Your GP may prescribe a different medicine or recommend you stop breastfeeding.
When you start taking venlafaxine
You are likely to feel better after taking venlafaxine for 1 to 2 weeks.
But usually you will not feel the full benefits for up to 6 weeks.
Do not stop taking venlafaxine just because you feel it is not helping your symptoms. Give the medicine at least 6 weeks to work.
Driving, cycling and operating machinery
Venlafaxine can affect your concentration. Do not drive, cycle or operate machinery until you know how the medicine makes you feel.
Check your blood sugar if you have diabetes
Monitor your blood sugar more often for the first few weeks of treatment if you have diabetes.
If you have diabetes, venlafaxine can make it more difficult to keep your blood sugar stable.
Your GP may adjust your diabetes treatment if your blood sugar levels change.
How and when to take venlafaxine
Take venlafaxine as recommended by your GP. Check with your GP or pharmacist if you're not sure.
If you are prescribed capsules, swallow them whole with water. Do not crush, cut, open, dissolve or chew the capsule.
Take the medicine with food at the same time each day.
Your GP might prescribe a lower dose if you have problems with your liver or kidneys.
Do not drink alcohol while you are 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.
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
Do not drive yourself to the ED. Get someone else to drive you or call 999 or 112 for an ambulance.
Bring the venlafaxine packet or leaflet and any remaining medicine with you.
If you take too much venlafaxine, you may:
- feel sleepy
- get sick (vomit)
- have a faster heartbeat
- have seizures or fits
- have blurred vision
How long you will need to take venlafaxine
Your GP is likely to recommend that you continue taking venlafaxine for at least 6 months after depression eases.
Depression can come back if you stop it too soon.
Stopping venlafaxine
Do not stop or reduce your dose of venlafaxine without speaking with your GP. Your GP will recommend reducing your dose gradually over several weeks, if you have been taking venlafaxine for a long time.
This is to help prevent any withdrawal symptoms you might get as a reaction to coming off the medicine.
These include:
- feeling dizzy
- feeling sick
- numbness or tingling in the hands or feet
- trouble sleeping
- feeling agitated or anxious
- headaches
- shaking
Side effects
Venlafaxine can cause side effects. But many people do not get side effects or they may be mild.
Common side effects
There are things you can do to help manage common side effects:
Feeling sick (nausea)
Stick to simple meals and do not eat rich or spicy food. If it carries on, tell your GP.
Headaches
Make sure you rest and drink fluids. Do not drink alcohol.
Ask your pharmacist to recommend a painkiller. Talk to your GP if the headaches last longer than a week or are severe.
Sweating
Try wearing loose clothing, use a strong anti-perspirant, and keep cool using a fan if possible. If there is no improvement after a week, speak to your GP.
Dry mouth
Chew sugar-free gum or suck sugar-free sweets.
Feeling dizzy
If venlafaxine makes you feel dizzy when you stand up, try getting up very slowly or stay sitting down until you feel better. If you begin to feel dizzy, lie down so that you do not faint, then sit until you feel better.
Do not drive, ride a bike or use tools or machinery if you feel dizzy.
Feeling sleepy
Do not drive, ride a bike or use tools or machinery if you're feeling sleepy. Do not drink alcohol as this will make you feel more tired. If this symptom does not go away after a week or two, ask your GP for advice.
Being unable to sleep (insomnia)
Take venlafaxine first thing in the morning.
Constipation
Get more fibre into your diet such as fresh fruit and vegetables and cereals, and drink plenty of water. Try to exercise, for example, by going for a daily walk or run. If this does not help, talk to your pharmacist or doctor.
Side effects are usually mild and go away after a couple of weeks.
Tell your GP or pharmacist if side effects bother you or do not go away.
Long-term side effects
For most people, venlafaxine is safe to take for a long time and there are no lasting effects.
A few people may get sexual side effects, such as problems getting an erection or a lower sex drive.
In some cases these can continue even after stopping the medicine. Speak to your GP if you are worried.
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 Health Products Regulatory Authority (HPRA): report an issue - hpra.ie
Serious side effects
Serious side effects from taking venlafaxine are not common.
Emergency action required: Call 112 or 999 or go to an emergency department (ED) immediately if you have:
- chest pain or pressure
- shortness of breath
- a fast or irregular heart beat
Urgent advice: Contact your GP urgently if you have:
- constant headaches, long-lasting confusion, weakness or frequent muscle cramps - these can be signs of low sodium levels in your blood
- feelings of overwhelming happiness (euphoria), excessive enthusiasm or excitement, or restlessness - you cannot sit or stand still
- unexplained muscle pain or weakness
- yellowing of your skin or the whites of your eyes (jaundice) - this can be a sign of liver problems
- changes in your eyesight, like blurred vision or dilated pupils
- dark vomit, blood in your pee or black or red poo, or you are coughing up blood
- bleeding from your gums or bruising that you cannot explain
- thoughts about harming yourself or ending your life
Non-urgent advice: Contact your GP if you have:
- weight gain or you lose weight without trying
- changes in your periods such as spotting, bleeding between periods or heavy bleeding
Serious allergic reaction
Emergency action required: Call 112 or 999 or go to an emergency department (ED) immediately if:
- you get a rash that is itchy, red, swollen, blistered or peeling
- you're wheezing
- you get tightness in your chest or throat
- you have trouble breathing or talking
- your mouth, face, lips, tongue or throat start swelling
Taking venlafaxine with other medicines
Venlafaxine can interfere with other medicines and increase the chance of side effects, such as serotonin syndrome.
Tell a GP or pharmacist before you start venlafaxine, if you're taking medicines:
- that affect your heartbeat
- for depression
- for pain
- for a cough, such as cough syrup
Do not take St John’s wort
Do not take herbal remedy St John's wort while you are taking venlafaxine. It will increase your risk of side effects, such as serotonin syndrome.
Serotonin syndrome happens when the level of serotonin in your brain is too high.
Emergency action required: Contact your GP or go to your nearest emergency department (ED) if
you get symptoms of serotonin syndrome including:
- 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 getting sick (vomiting)
Venlafaxine and recreational drugs
Using cannabis while you’re taking venlafaxine can give you a fast heartbeat and make drowsiness worse. This is especially the case in people who have just started taking venlafaxine.
Methadone can make sleepiness worse with venlafaxine. It may be dangerous to take venlafaxine with:
- stimulants - such as MDMA (ecstasy) or cocaine
- hallucinogens - such as LSD
- novel psychoactive substances (sometimes called legal highs) - such as mephedrone
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).
