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Drug Class: Commonly Known As: Category:
Serotonin and Noradrenaline Reuptake Inhibitors (SNRI) efexor Adult

venlafaxine - Side Effects, Precautions, and Contraindications

What side effects can venlafaxine cause?

Side effects which generally affect up to 10% of patients include:

  • Nausea or vomiting
    • Take the medication with or after food.
    • Take small but frequent meals and avoid fatty or spicy food
  • Difficulty sleeping
    • Discuss with your doctor and take the medication in the morning instead.
    • Avoid daytime naps, listen to relaxing music at bedtime.
    • Limit caffeine intake at least 8 hours before bedtime.
    • Avoid over eating and drinking just before bed
  • Dry mouth
    • Chew sugar-free gum, suck on sugar-free hard candies or ice chips, sip water regularly
  • Constipation
    • Drink more water (if you do not have any fluid restriction), eat more high-fibre foods, and exercise regularly
    • Consult your doctor or pharmacist if you need medication to relieve your condition.
  • Dizziness
    • Get up slowly from a sitting or lying down position
  • Mild nervousness
    • May occur at the start of treatment and improves over time
  • Headache, loss of appetite, weight loss, increased blood pressure, increased sweating, decreased sexual drive or ability
    • Speak to your doctor if any of these affect your daily life

Most of the side effects listed here will improve with time. Speak with your doctor if they continue, get worse or are affecting your daily life.

Very rarely (affect less than 1% of patients) this medication may cause:

  • Fits (seizures)
  • Unexplained fever, confusion, severe weakness, uncontrolled movements or muscle spasms (signs and symptoms of Serotonin syndrome
  • Blurred vision
  • Fast or uneven heartbeat, chest pain
  • Unusual bruising or bleeding

The symptoms of a drug allergy include one or more of the following:

  • Swollen face/eyes/lips/tongue
  • Difficulty in breathing
  • Itchy skin rashes over your whole body

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

Before taking venlafaxine, what precautions must I follow?

Inform your healthcare professional if:

  • You are allergic to this medication or any of the other ingredients of this medication
  • You are pregnant, planning to become pregnant, or breastfeeding. If you are pregnant and/or breastfeeding, your doctor would have discussed the potential benefits and side-effects with you and should you have further questions or concerns, do consult your doctor.
  • You have or have ever had:
  • Other drug allergies
    • Heart, kidney or liver disease
    • Medical conditions such as high blood pressure, fits (seizures), increased eye pressure (glaucoma), low sodium in the blood (hyponatremia) or bleeding problems
    • Other mental health conditions such as bipolar disorder or abnormally high or excited mood (mania)
    • Been taking other medications for low mood in the past 2 weeks.

Venlafaxine may increase your blood pressure. It is important to maintain regular check-ups with your doctor.


If you notice any changes in your mental condition especially in the first few weeks of treatment and during dose changes, you need to check with your doctor immediately. Do watch for any of the following changes in mental condition:

  • New or increasing thoughts of harming yourself

  • Worsening anxiety, restlessness, violent behaviour, or

  • Other changes in mood or behaviour.

Be sure that your family or caregiver are also aware of the above symptoms so they can call your doctor if you are unable to seek treatment on your own.

What food or medicine must I avoid when I take venlafaxine?

Avoid drinking alcohol while taking this medication as it may make you feel very drowsy. This medication may interact with other medications. If you intend to take any over the counter medication, supplements, herbal remedy or traditional Chinese medicine, consult your doctor or healthcare professional first to confirm that it is safe to take with Venlafaxine.

venlafaxine - Additional Information

  • Tags: Venlafaxine
  • Updated on Tuesday, June 30, 2020
  • Article contributed by PSS National Medication Information Workgroup PSS National Medication Information Workgroup

    The information provided is not intended as medical advice. Terms of use. Information provided by SingHealth

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