Venlafaxine is from of a group of antidepressants called serotonin and noradrenaline reuptake inhibitors, or SNRIs. It is thought to work by increasing the levels of mood-enhancing chemicals called serotonin and noradrenaline in the brain.
Venlafaxine can help people recover from depression, and has fewer side effects than some older antidepressants.
It comes as tablets and capsules which are available only on prescription.
Who can take venlafaxine
Most adults can take venlafaxine.
If you have diabetes, venlafaxine can make it more difficult to keep your blood sugar stable. Your doctor may recommend that you monitor your blood sugar level more often for the first few weeks of treatment so they can adjust your diabetes treatment if necessary.
Venlafaxine is not suitable for everyone. Check with your doctor before taking it if you:
- have ever had an allergic reaction to venlafaxine or any other medicine
- have a heart problem – venlafaxine can make your heart beat faster or cause an irregular heartbeat (arrhythmia)
- are trying to become pregnant, are already pregnant or you are breastfeeding
- have glaucoma – venlafaxine can increase the pressure in your eye
- have epilepsy or are having electroconvulsive treatment – venlafaxine may increase your risk of having a fit or seizure
Dosage and strength
The usual starting dose for venlafaxine is 75mg a day but your doctor may gradually increase it to a maximum dose of 375mg.
If you have problems with your liver or kidneys your doctor might prescribe a lower dose.
Standard tablets come as 37.5mg or 75mg tablets. Slow release tablets and capsules come as 75mg and 150mg.
You will usually take standard tablets twice a day, once in the morning and once in the evening.
You will usually take slow release tablets or capsules once a day. You can take them at any time as long as you stick to the same time every day. If you have trouble sleeping, it's best to take it in the morning.
How long to take it for
Once you're feeling better it's likely that you will continue to take venlafaxine for several more months. Most doctors recommend that you take antidepressants for 6 months to 1 year after you no longer feel depressed. Stopping before that time can make depression come back.
The decision to stop your treatment or carry on will depend on what symptoms you have and how serious they are. It will also depend on whether it's a one-off problem or one that keeps coming back, how well venlafaxine works for you, and whether you have had any bad side effects.
If you forget to take it
If you occasionally forget to take a dose, just take your next dose at the usual time. Never take 2 doses at the same time to make up for a forgotten one.
If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.
Your doctor 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
If you take too much
The amount of venlafaxine that can lead to an overdose varies from person to person.
Taking too much can cause symptoms such as:
- feeling sleepy
- feeling sick (nausea) or being sick (vomiting)
- a faster heartbeat
- feeling dizzy
- fits or seizures
- you take more than your prescribed dose of venlafaxine
If you need to go to a A&E, do not drive yourself. Get someone else to drive you or call for an ambulance.
Take the venlafaxine packet, or the leaflet inside it, plus any remaining medicine with you.
Common side effects
These common side effects of venlafaxine happen in more than 1 in 100 people. There are things you can do to help cope with them:
If this advice does not help and any of these side effects bother you, talk to your doctor or pharmacist.
It's not common, but some people (less than 1 in 100) may have serious side effects when taking venlafaxine.
Book an appointment with your doctor if:
- you gain weight or lose weight without trying
- you have changes in your periods such as heavy bleeding, spotting, or bleeding between periods
Call your doctor or contact 111 now if:
- you get constant headaches, long-lasting confusion, weakness, or frequent muscle cramps – these can all be signs of low sodium levels in your blood you have feelings of overwhelming happiness (euphoria), excessive enthusiasm or excitement, or a feeling of restlessness that means you cannot sit or stand still
- you have unexplained muscle pain or weakness
- the whites of your eyes or skin turn yellow, although this may be less obvious on black or brown skin – this can be a sign of liver problems
- you have any changes in your eyesight, like blurred vision or dilated pupils
- you cough up blood or have blood in your pee
- you have black or red poo, or blood in your vomit – these can be signs of bleeding in the stomach
- you are bleeding from the gums, or have bruises that appear without a reason or that get bigger
- you get shortness of breath, or a fast or irregular heart beat
- you have thoughts about harming yourself or ending your life
- you get chest pain or pressure in your chest, shortness of breath, or a fast or irregular heart beat
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to venlafaxine.
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 doctor if you are worried.
Other side effects
These are not all the side effects of venlafaxine. For a full list, see the leaflet inside your medicine packet.
Venlafaxine and pregnancy
There’s no good evidence that taking venlafaxine in early pregnancy will affect your baby’s development.
When venlafaxine is taken in the weeks before delivery it can sometimes cause short-term withdrawal symptoms and, very rarely, breathing problems in the baby. Your baby will be checked after birth and given additional care if needed.
Taking venlafaxine in the last month of pregnancy may slightly increase your risk of bleeding after delivery. However, because this side-effect is rare, it's not a reason to stop taking venlafaxine for most pregnant women.
It’s important that your mental health is treated since this can impact on yours and your baby’s wellbeing. Depression and anxiety can sometimes get worse during pregnancy and after your baby has been born.
Speak to your doctor if you become pregnant. They will talk through the risks and benefits so you can decide on the best treatment for you and your baby.
If your doctor or health visitor says your baby is healthy, you can take venlafaxine while breastfeeding.
Venlafaxine passes into breast milk in small amounts and has been linked with side effects in very few breastfed babies. It has been used by many breastfeeding mothers without any problems.
It's important you keep taking venlafaxine to keep you well. Breastfeeding will also benefit both you and your baby.
If you notice that your baby seems unusually sleepy, is not feeding as well as usual, seems irritable, or if you have any other concerns about your baby, then talk to your health visitor, midwife, doctor or pharmacist as soon as possible.
Venlafaxine and fertility
There's no clear evidence to suggest that taking venlafaxine reduces fertility in men, but it may affect the menstrual cycle in women.
Speak to a pharmacist or your doctor if you're trying to get pregnant. They may want to review your treatment.
Cautions with other medicines
Some medicines can affect the way venlafaxine works and increase the chances of you having side effects.
Tell your doctor if you're taking these medicines before you start venlafaxine:
- any medicines that affect your heartbeat – as venlafaxine can make your heart beat faster or cause an irregular heartbeat
- any other medicines for depression – some rarely used antidepressants can affect venlafaxine and cause very high blood pressure even if they have not been taken few weeks
Do not take St John's wort, a herbal remedy for depression, while you are being treated with venlafaxine because it increases your risk of side effects.
There's not enough information to say that other complementary medicines and herbal remedies are safe to take with venlafaxine. They're not tested in the same way as pharmacy and prescription medicines. They're generally not tested for the effect they have on other medicines.
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