Venlafaxine

Sounds like 'ven-la-FAX-een'

Easy-to-read medicine information about venlafaxine – what it is, how to take venlafaxine safely and possible side effects.

Type of medicine Also called
  • Antidepressant
  • Belongs to a group of medicines known as serotonin-noradrenaline reuptake inhibitors (SNRIs)
  • Enlafax XR®
  • Arrow-Venlafaxine XR ®
  • Efexor-XR ®

What is venlafaxine?

Venlafaxine is used to treat severe depression, anxiety disorder or panic disorder. It is one of a group of medicines known as serotonin-noradrenaline reuptake inhibitors (SNRIs). It is believed that SNRIs work by increasing the activity of certain chemicals working in our brains called neurotransmitters. They pass signals from one brain cell to another. Although we don’t know for certain, the neurotransmitters that are most likely to be involved in depression and some other conditions are thought to be serotonin and noradrenaline. Read more about antidepressants. In New Zealand, venlafaxine is available as tablets and capsules.

Dose

  • The dose of venlafaxine will be different for different people. Your doctor will usually start you on a low dose and if  you need to, will increase your dose slowly. This allows your body to get used to the medicine and reduces side effects.
  • Always take your venlafaxine exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much venlafaxine to take, how often to take it, and any special instructions.

How to take venlafaxine

  • Take venlafaxine once a day, at the same time each day, either in the morning OR in the evening. You can generally take it at a time to suit you, but try to take your doses at the same time of day, each day.
  • It is best to take venlafaxine with food. 
  • Swallow your venlafaxine capsule or tablet whole — do not crush or chew. This will release all the medicine at once and cause side effects.
  • If you forget to take your dose and if it is  more than 12 hours late, wait until the next day and take your normal dose then. Do not take double the dose. Otherwise, if it is less than 12 hours late, take it as soon as you remember, and then go back to taking as you would normally.
  • Keep taking your venlafaxine every day. It may take a few weeks or months before you notice the full benefits of venlafaxine.
  • If you think venlafaxine is not working for you, do not stop taking it suddenly; speak to your doctor or nurse before stopping. It is usually best to stop taking venlafaxine very slowly to avoid side effects.

Precautions – before starting venlafaxine

  • Do you have any heart problems such as irregular heart beat?
  • Do you have problems with your kidneys?
  • Do you have epilepsy?
  • Do you have bipolar disorder or a family history of mania?
  • Do you have high blood pressure (hypertension)?
  • Do you have diabetes? 
  • Are you pregnant or breastfeeding?
  • Do you have a bleeding disorder or stomach ulcer?
  • Are you taking any other medicines, including medicines you can buy without a prescription, such as herbal and complementary medicines or pain relief medicines?

If so, it’s important that you tell your doctor or pharmacist before you start venlafaxine. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

Precautions – while taking venlafaxine

  • Alcohol:  avoid alcohol while you are taking venlafaxine, especially when you first start treatment. Drinking alcohol while taking venlafaxine can cause drowsiness and affect concentration, putting you at risk of falls and other accidents. It can also cause agitation, aggression and forgetfulness. If you do drink alcohol, drink only small amounts and see how you feel. Do not stop taking your medication.
  • High blood pressure (hypertension): if you have high blood pressure, you may need to check your blood pressure more often, especially when you first start venlafaxine, because it can cause an increase in blood pressure.
  • Sun protection: venlafaxine can make your skin more sensitive to the sun. You may get a burning, tingling feeling on your skin when you are in the sun, or you may notice a darker tan or redness. When outside, protect your skin by using a good sunscreen (SPF 50+) and wearing a wide-brimmed sunhat and long-sleeved shirts and trousers.

Possible side effects

Like all medicines, venlafaxine can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Suicidal behaviour

The use of antidepressants has been linked with self harm or suicidal thoughts and behaviour. Children, teenagers, young adults and people with a history of suicidal behaviour are most at risk. This is most likely during the first few weeks of starting treatment or if the dose is changed. It is important to look out for signs of suicidal behaviour such as suicidal thoughts, self-harm, worsening of low mood, agitation or aggression. If you notice any of these signs, contact your doctor immediately. 

Sexual side effects

Venlafaxine can cause reduced sexual drive, lack of libido and problems keeping an erection. It’s important to talk to your healthcare provider if you get these effects, as they can be difficult to deal with and may not go away. Your healthcare provider may be able to suggest treatment or may reduce the dose of venlafaxine or change to a different antidepressant.

Other side effects

Side effects What should I do?
  • Feeling sick (nausea) or vomiting
  • Stomach upset
  • Try taking venlafaxine after food.
  • Tell your doctor if troublesome and the symptoms are ongoing
  • Feeling sleepy, drowsy, or tired
  • Try taking venlafaxine in the evening
  • Be careful when driving or using tools until you know how this medicine affects you
  • Tell your doctor if troublesome
  • Headache
  • Dry mouth
  • Increased sweating
  • Trouble sleeping


  • These are quite common when you first start taking venlafaxine and usually go away with time
  • Tell your doctor if troublesome
  • Weight changes
  • Tell your doctor 
  • Suicidal thoughts, thoughts of harming yourself, or worsening depression
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • Changes in heart beat such as fast heart rate or irregular heart beat  
  • Seizures
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • Signs of serotonin syndrome such as feeling agitated and restless, heavy sweating, shivering, fast heart rate or irregular heart beat, headache, diarrhoea and rigid or twitching muscles
  • You are at increased risk of serotonin syndrome if you recently started taking venlafaxine or recently increased the dose
  • Tell your doctor immediately or ring HealthLine 0800 611 116

Interactions

Venlafaxine interacts with many other medications and herbal supplements (such as St. John's wort) so check with your doctor or pharmacist before starting venlafaxine or before starting any new medicines.

Learn more

The following links have more information on venlafaxine.

Medsafe consumer information sheets: Enlafax SRArrow-Venlafaxine XR , Efexor XR

New Zealand Formulary Patient Information: venlafaxine

Pharmac Your brand of medicine is changing

References

  1. Venlafaxine New Zealand Formulary
  2. QT Prolongation with antidepressants Medsafe NZ, 2013
  3. Venlafaxine and photosensitivity Medsafe NZ, 2016
  4. The role of medicines in the management of depression in primary care BPAC, 2017
Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 19 Feb 2018