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Desvenlafaxine (Pristiq®)

Desvenlafaxine (Pristiq® and generic forms) belongs to a group of medications called “antidepressants.”

What is this medication used for?

Desvenlafaxine is not approved by Health Canada for use in children and adolescents.

However, desvenlafaxine may help treat depression when other treatments have not been effective or tolerated. It may also be used to treat several other conditions.

When potential benefits outweigh risks, desvenlafaxine may be prescribed “off-label.” Learn more about off-label medication use:

Tell your doctor or pharmacist if you:

  • Have allergies or bad reactions to a medication
  • Take (or plan to take) other prescription or non-prescription medications, including natural medicines. Some medications interact with desvenlafaxine. Your doctor may adjust medication doses or monitor for side effects
  • Have a history (or family history) of heart, kidney or liver disease, seizures, bipolar disorder or glaucoma
  • Miss a menstrual period, are pregnant, breast-feeding or planning a pregnancy
  • Use alcohol or street drugs. Taking desvenlafaxine together with certain substances may cause a bad reaction. Learn more at

When will the medication start to work?

You (or your family members) may notice some improvements in sleep, appetite and energy within the first 2 weeks. However, it may take 3 to 6 weeks before you begin to feel better. Full beneficial effects may take 4 to 8 weeks or longer.

Desvenlafaxine takes time to work. Continue taking desvenlafaxine as prescribed, even if you are feeling better. Talk with your doctor before you increase, decrease or stop taking desvenlafaxine.

This medication is not addictive. Do not stop taking it before talking to your doctor.

How do I take this medication?

Desvenlafaxine is usually taken once daily with or without food, at the same time each day. Usually, you will stay on the dose of desvenlafaxine you start with, but you may also be asked to increase the dose.

Extended-release desvenlafaxine tablets should be swallowed whole with fluid. The tablets should not be divided, crushed, chewed or placed in water. The medication is contained within a non-absorbable shell which will be eliminated from your body, usually in your stool. Do not be concerned if you see a tablet-shaped object in your stool.

Possible common or serious side effects:

Side effects may be more common when starting a medication or after a dose increase. Talk to your doctor, nurse or pharmacist if any side effect concerns you.

  • Nausea, vomiting, diarrhea or constipation
  • Dizziness, drowsiness or headache
  • Fatigue or lack of energy
  • Trouble sleeping or abnormal dreams
  • Increased sweating
  • Increased blood pressure
  • In adolescents/adults: changes in sexual performance or interest

Contact your doctor immediately if you experience:

  • Thoughts of hurting yourself, hostility or suicide
  • Changes in mood to an unusual state of excitement, irritability or happiness
  • Confusion or difficulty remembering things along with muscle aches, stiffness, and lack of coordination
  • Uncomfortable sense of inner restlessness or agitation
  • Unexpected rash, seizure, fever or excessive sweating
  • Unusual bruising or bleeding

What precautions should my doctor and I be aware of when taking this medication?

  • While taking desvenlafaxine, if you feel dizzy, drowsy or slowed down, do not drive a car or operate heavy machinery. Alcohol could make this worse. Try to avoid alcohol while taking desvenlafaxine.
  • Desvenlafaxine and medications like it are associated with a rare side effect called “serotonin syndrome,” especially when used in combination with other serotonergic drugs such as MAO-inhibitors, triptans and most other antidepressants. Symptoms include diarrhea, sweating, increased heart rate, tremors, severe muscle stiffness and increased agitation.
  • Do not to stop taking desvenlafaxine suddenly. Stopping abruptly is associated with “antidepressant discontinuation syndrome.” This involves flu-like symptoms, trouble sleeping, nausea, irritability, headache and abnormal sensations that feel like electric shocks, burning, tingling or numbness. If stopping or changing medications, discuss with your doctor about how to do so safely.

How does this medication work?

Desvenlafaxine is a Serotonin and Norepinephrine Reuptake Inhibitor (SNRI). Like other SNRIs, desvenlafaxine increases levels of the brain chemicals serotonin and norepinephrine. These brain chemicals do not function properly in people who have depression. The exact way that desvenlafaxine improves symptoms of depression is not known.

What special instructions should I follow while using this medication?

  • Keep all appointments with your doctor and the lab.
  • Your doctor may want to talk to you within 1-2 weeks of starting desvenlafaxine, and meet with you over time to make sure it is working well for you and check for side effects.
  • Do not allow anyone else to use your medication.

What should I do if I forget to take a dose of this medication?

If you forget to take a dose of desvenlafaxine, take the missed dose as soon as you remember. However, if it is within 4 hours of your next schedule dose, skip the missed dose and continue with your regular schedule. DO NOT double your next dose to try to ‘catch up’.

How do I store this medication?

Keep desvenlafaxine in the original container, stored at room temperature away from moisture and heat and protected from light. Keep desvenlafaxine out of reach and sight of children.

How well does the medication work in children and adolescents?

Desvenlafaxine has been studied in children and adolescents with depression and has been shown to be no better than placebo (an inactive pill). Desvenlafaxine is sometimes prescribed for children and adolescents when other treatments have not been effective or when genetic testing indicates that their bodies may break down (metabolize) other antidepressants too slowly or too quickly. Whenever possible, the addition of talk therapy, such as Interpersonal Therapy (IPT) for depression or Cognitive Behavioural Therapy (CBT), may help increase the potential for benefit.

How long should I take the medication for?

This depends on the symptoms you have, how frequently they occur and how long you have had them. Most people need to take desvenlafaxine for at least 6 months. This allows time for symptoms to stabilize and function to improve. After this time, you and your doctor can discuss the benefits and risks of continuing treatment.

If you have had several episodes of severe depression and you tolerate desvenlafaxine well, you may be asked to take desvenlafaxine on an ongoing basis. Continuing treatment will significantly decrease the chance that you may have another episode of depression.

Do not increase, decrease or stop taking desvenlafaxine without discussing it with your doctor, even if you are feeling better. If you stop taking desvenlafaxine suddenly, it is possible that your symptoms may return or you may have a bad reaction.

TIP: Use the Kelty Mental Health Antidepressant Monitoring Form for Children and Adolescents to help measure your progress on this medication.

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