Pristiq (desvenlafaxine) is a prescription drug that’s used to treat major depressive disorder in adults. Pristiq can cause side effects that range from mild to serious. Examples include nausea and constipation.

Some people may experience mild to serious side effects during Pristiq treatment. Examples of Pristiq’s commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section below.

Read on to learn about other potential mild and serious side effects of Pristiq.

Pristiq may cause mild side effects. Examples of mild side effects that have been reported with Pristiq include:

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after taking Pristiq. But it’s unclear whether this side effect was reported in studies or after the drug was made available on the market.

In most cases, these side effects should be temporary. And some may be easily managed, too. But if you have any symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop taking Pristiq unless your doctor recommends it.

Pristiq may cause mild side effects other than the ones listed above. See the Pristiq prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Pristiq, visit MedWatch.

Pristiq can cause serious side effects, though these are usually rare. Serious side effects that have been reported with Pristiq are listed below. Some of these side effects were reported in studies of Pristiq. But others were reported after the drug became available on the market.

* Pristiq has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effects explained” section below.
† To learn more about this side effect, see the “Side effects explained” section below.
‡ An allergic reaction is possible after taking Pristiq. But it’s unclear whether this side effect was reported in studies or after the drug was made available on the market.

If you develop serious side effects while taking Pristiq, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Get answers to some frequently asked questions about Pristiq’s side effects.

Does Pristiq cause weight gain?

It’s possible. Although rare, weight gain has been reported with Pristiq. But it’s unclear whether this side effect was reported in studies or after the drug was made available on the market.

It’s important to note that weight changes, including weight gain, can be a symptom of depression.

If you experience weight gain while taking Pristiq, talk with your doctor. They may have tips to help with this side effect.

If I suddenly stop taking Pristiq, will I have withdrawal symptoms?

Yes, it’s possible. Withdrawal symptoms may be a side effect of stopping Pristiq, and they can be mild or serious. (Withdrawal symptoms are uncomfortable side effects that can occur when you stop taking a drug your body is used to.) Some of the mild symptoms of withdrawal include:

Some serious symptoms of withdrawal include:

These side effects are more likely to happen if you stop taking Pristiq suddenly. If you want to stop taking Pristiq, talk with your doctor first. They’ll likely recommend that you take a smaller dose for a while rather than stopping Pristiq abruptly. It may take several months to stop taking Pristiq completely.

Will my risk of side effects be higher with the 100-mg dose of Pristiq than with lower doses of the drug?

It’s possible. During studies of Pristiq, people took different doses of the drug. The side effects that were reported were the same for each dosage. But more people who took the 100-milligram (mg) dose reported certain side effects than those who took the 50-mg dose. Some of these side effects were:

  • dry mouth
  • sleepiness
  • trouble sleeping
  • certain sexual side effects*
  • nausea*

If you have questions about side effects for a specific dose of Pristiq, talk with your doctor or pharmacist.

* To learn more about this side effect, see the “Side effects explained” section below.

Learn more about some of the side effects Pristiq may cause.

Risk of suicidal thoughts and actions

Pristiq carries a boxed warning about the risk of suicidal thoughts and actions in children, adolescents, and adults ages 24 years and younger. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

Antidepressants such as Pristiq may increase the risk of suicidal thoughts and actions in people under 25 years of age. The FDA has not approved the use of Pristiq in people ages 18 years or younger.

Symptoms of suicidal thoughts and actions include:

What might help

Keep track of how you feel while taking Pristiq. If you experience any of the symptoms listed above while taking Pristiq, tell your doctor right away.

Consider letting people close to you know about this Pristiq side effect and its symptoms. They can also help you watch out for these symptoms.

If you’re 18–24 years of age, your doctor may monitor you more closely for symptoms of suicidal thoughts and actions during Pristiq treatment.

Help is out there

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you are not in the same household, stay on the phone with them until help arrives.

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Sexual side effects

Antidepressants such as Pristiq may cause sexual side effects. In studies of the drug, males* reported:

In studies of the drug, females* reported:

* In this article, we use the terms “male” and “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

What might help

Over time, sexual side effects may lessen on their own. Sometimes, switching to a different antidepressant may help. If you experience any sexual side effects while taking Pristiq, tell your doctor. They can suggest ways to help ease sexual side effects.

Nausea

In studies, nausea was a common side effect of Pristiq. By itself, nausea may be considered a mild side effect. But it can be a symptom of withdrawal, which may occur if you stop taking Pristiq suddenly. (For more information, see the “FAQ about Pristiq’s side effects” section above.)

Nausea may also be a symptom of serotonin syndrome. This is a serious condition that can happen when too much serotonin builds up in the body. If you take Pristiq with other drugs that affect your body’s serotonin level, the risk of serotonin syndrome may be higher.

Other symptoms of serotonin syndrome include:

What might help

If you have nausea with Pristiq, the following tips may help ease this side effect:

  • Take your dose with some crackers or toast.
  • Try drinks or foods that contain ginger.
  • Ask your doctor about medications that can help decrease nausea.

If your nausea is severe or occurs with the symptoms of serotonin syndrome listed above, seek immediate medical care.

Headache

Headache was a common side effect in short-term studies of Pristiq. This side effect was usually mild.

This side effect may also occur if you suddenly stop Pristiq. (For more information, see the “FAQ about Pristiq’s side effects” section above.)

Headaches may be a symptom of a low blood level of sodium. This is a side effect of certain antidepressants such as Pristiq, and it can be a serious problem. Older adults (ages 65 years and older) and people who take diuretics may have a higher risk of this side effect. Symptoms to watch out for include:

What might help

Mild headaches may lessen a few weeks after starting Pristiq. But if this side effect continues to bother you, talk with your doctor. They may recommend medications to treat your headaches.

If your headaches occur with the other symptoms of a low blood level of sodium listed above, seek immediate medical treatment.

Constipation

Constipation was a common, mild side effect in studies of Pristiq.

What might help

Constipation usually goes away after taking Pristiq for a few weeks. Drinking more water and mild exercise may help with this side effect.

If you experience constipation that becomes severe, talk with your doctor. They may recommend changes in your diet or medications to help relieve this side effect.

Allergic reaction

Like most drugs, Pristiq can cause an allergic reaction in some people. It’s unclear whether this side effect was reported in studies before or after the drug was made available on the market.

Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, usually in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest treatment options to manage your symptoms. Examples include:

  • an antihistamine you take by mouth, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Pristiq, they’ll decide if you should continue taking it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Pristiq, they may have you switch to a different treatment.

Keeping track of side effects

During your Pristiq treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how it affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Pristiq affects you. They can then use this information to adjust your treatment plan if needed.

Pristiq comes with several warnings.

Boxed warning: Risk of suicidal thoughts and actions

Pristiq has a boxed warning for the risk of suicidal thoughts and actions in children, adolescents, and adults ages 24 years and younger. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

To learn more, see the “Side effects explained” section above.

Other warnings

Pristiq may cause drug-condition interactions. This means that Pristiq may not be right for you if you have certain medical conditions. Other factors may also affect whether Pristiq is a good treatment option for you.

Talk with your doctor about your health history before starting Pristiq. The list below includes factors to consider.

High blood pressure: Pristiq can cause your blood pressure to increase. If you have high blood pressure, your doctor may prescribe medication to treat it before you start taking Pristiq. Then they’ll monitor your blood pressure to make sure it’s well-managed. If your blood pressure remains high, your doctor may adjust your dosage of Pristiq or recommend a different antidepressant.

Heart disease: If you have heart disease, Pristiq may make it worse. Pristiq can increase your blood pressure, which may worsen heart disease. If you have a history of heart disease or high blood pressure, tell your doctor before starting Pristiq treatment.

Stroke or ministroke: Pristiq can increase your blood pressure, so it may increase your risk of stroke if you’ve had one before. If you’ve had a stroke or if you’ve had any problems with high blood pressure, let your doctor know. This will help them determine whether it’s safe for you to take Pristiq.

Bleeding problems: Medications like Pristiq may increase your risk of bleeding. If you take medications that increase bleeding, your risk may be greater. Before you take Pristiq, make sure your doctor knows all of the medications you take. Your risk of bleeding may also be higher if you take Pristiq while pregnant. To learn more, see the “Pregnancy and breastfeeding while taking Pristiq” section below.

Angle-closure glaucoma: Pristiq may dilate the pupils in the eye, which can cause an episode of angle-closure glaucoma in people with narrow eye angles. This condition is a medical emergency that may cause severe eye pain and vision loss. Because of this, doctors will likely not prescribe Pristiq to anyone with narrow eye angles. Your doctor may recommend that you receive an eye exam before taking Pristiq.

Mania, hypomania, or bipolar disorder: Pristiq may not be the right medication for people who have had mania, hypomania, or bipolar disorder. It also may not be safe for people who have a family history of these mental health conditions. If you have bipolar disorder, Pristiq can increase your risk of a manic episode. Before you start Pristiq treatment, tell your doctor about any mental health conditions you or close family members have had.

Allergic reaction: If you’ve had an allergic reaction to Pristiq or any of its ingredients, your doctor will likely not prescribe Pristiq. Ask them what other medications are better options for you.

Seizures or epilepsy: Pristiq was not studied in people with a history of seizures or epilepsy. If you’ve ever had a seizure or have epilepsy, tell your doctor. They’ll let you know if Pristiq is safe for you to take.

Low sodium level: Pristiq can lower the blood level of sodium, which can become a serious problem. Older adults (ages 65 years and older) or people who take diuretics may have a higher risk of this side effect. If you are an older adult or take a diuretic, or have had problems with a low sodium level in the past, your doctor will let you know whether it’s safe to take Pristiq.

Liver problems: If you have liver problems, your body may have trouble getting rid of Pristiq. Before you start treatment, tell your doctor about any liver problems you have or have had. They may prescribe a lower dosage of Pristiq.

Kidney problems: If you have kidney problems, your body may have trouble getting rid of Pristiq. Before you start treatment, tell your doctor about any kidney problems you have or have had. They may recommend that you take a lower dosage of Pristiq.

High cholesterol or triglycerides: Pristiq may increase cholesterol or triglycerides in certain people. If you’ve had high cholesterol or triglycerides or take medication to treat these conditions, tell your doctor. They may recommend more frequent blood tests to check levels of these substances while you’re taking Pristiq.

Alcohol and Pristiq

You should not take Pristiq with alcohol. Alcohol may increase your risk of side effects and may make depression worse.

Before you start taking Pristiq, talk with your doctor if you drink alcohol. They may suggest ways to stop drinking or recommend a different medication for you.

Pregnancy and breastfeeding while taking Pristiq

Before taking Pristiq, talk with your doctor if you are pregnant or plan to become pregnant. They can help you decide whether Pristiq is the best choice for you during this time.

Certain antidepressants can increase the risk of preeclampsia or bleeding complications during or after pregnancy. Taking Pristiq in the third trimester of pregnancy may cause withdrawal symptoms in your newborn. (Withdrawal symptoms are uncomfortable side effects that can occur when you stop taking a drug your body is used to.)

If you become pregnant during treatment with Pristiq, ask your doctor about registering with the National Pregnancy Registry for Antidepressants. This registry gathers data from people who’ve taken Pristiq while pregnant. This data can help determine the safety of taking antidepressants such as Pristiq during pregnancy. To learn more or register, you can call 844-405-6185.

Small amounts of Pristiq may pass into breast milk. It’s not known whether Pristiq is safe to take during breastfeeding. If you’re breastfeeding or planning to breastfeed, talk with your doctor about ways to safely feed your child during treatment with Pristiq.

Pristiq may help treat your depression symptoms. Some people have mild side effects from the drug, such as nausea and constipation. More serious side effects from Pristiq aren’t common.

If you have questions about Pristiq’s side effects, talk with your doctor or pharmacist. Here are a few questions to ask about treatment with Pristiq:

  • Is my risk of sexual side effects higher when I first start treatment?
  • Does my risk of nausea and vomiting depend on what dose I take?
  • Does Pristiq have more side effects than other drugs that treat my condition?

To learn more about Pristiq, see these articles:

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.