Desvenlafaxine (Pristiq): dosage, uses, side effects

We all feel blue from time to time. But if you’re struggling with depression, you know the feelings of sadness and hopelessness can be overwhelming. Just getting through the day can be a challenge. Fortunately, it doesn’t have to be this way. Effective treatment options are available to get you feeling like yourself and back to the things you enjoy doing. Find out how one option—Pristiq—may be able to help. 

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Pristiq (desvenlafaxine) is a prescription medication used to treat depression. Pristiq belongs to a group of antidepressants called serotonin-norepinephrine reuptake inhibitors, or SNRIs. SNRIs work by increasing levels of serotonin and norepinephrine—two chemical messengers that send signals from one part of the body to another (Pfizer, 2018). Researchers believe that low levels of serotonin and norepinephrine contribute to depression (Sahli, 2016). 

Pristiq is approved by the U.S. Food and Drug Administration (FDA) for the treatment of major depressive disorder (MDD) (Pfizer, 2018). If your healthcare provider has prescribed Pristiq to treat your depression, keep in mind that you may not see an improvement in your symptoms right away. Some people begin to feel better within two weeks of starting Pristiq, but it may take six weeks or longer to see the full effects (Machado-Vieira, 2010). 

Pristiq can also be used “off-label” to treat other conditions, meaning the FDA didn’t explicitly approve it for those uses. A healthcare provider can prescribe drugs for an unapproved use if they decide that it’s the proper treatment for their patient. 

Healthcare providers sometimes prescribe Pristiq off-label to treat the hot flashes and night sweats associated with menopause—especially for women that can’t take estrogen (Naseeruddin, 2021). 

Pristiq is generally well-tolerated, but side effects can occur. The most common side effect reported in clinical trials was nausea. Nausea is often the worst during the first week of treatment but tends to go away after that (Liebowitz, 2008). If you experience nausea with Pristiq, taking your dose with food may help. 

Other common side effects of Pristiq include (Liebowitz, 2008; Pfizer, 2018):

• Anxiety 

• Constipation 

• Decreased appetite 

• Dizziness 

• Drowsiness 

• Dry mouth 

• Excessive sweating 

• Sexual dysfunction (ex. reduced sex drive, ejaculation problems) 

• Trouble sleeping 

Be sure to let your healthcare provider know if any of these side effects don’t go away or affect your ability to take your medication. 

Less commonly, Pristiq may cause rare and sometimes serious side effects, such as (Pfizer, 2018):

• Allergic reactions: Seek medical attention if you experience a rash, hives, swelling, or difficulty breathing. 

• Glaucoma: Let your healthcare provider know about any eye problems you have. 

• Low sodium levels: This is a potential concern, especially if you are older or take diuretic medications (sometimes called “water pills”). 

• Lung problems: Contact your healthcare provider right away if you develop trouble breathing, a cough, or chest discomfort.  

Pristiq is available in doses of 25 mg, 50 mg, and 100 mg extended-release tablets. The typical starting dose for depression is 50 mg daily. Your healthcare provider may gradually increase your dose depending on your symptoms and side effects up to a maximum dose of 100 mg daily. Because Pristiq is formulated as an extended-release tablet, it is important not to crush or chew your dose—doing so can affect how quickly the medication is released into your body and cause side effects (Pfizer, 2018). 

Before starting Pristiq, be sure to review these warnings and discuss any concerns with your healthcare provider.  

Suicidal thoughts and behaviors

The FDA has labeled all antidepressants, including Pristiq, with a boxed warning—their strongest warning—regarding the increased risk of suicidal thoughts and behaviors in children and young adults. People over the age of 24 did not show an increased risk, and individuals 65 and older had a decrease in these thoughts and behaviors. The FDA notes that untreated depression can also lead to suicidal thoughts and behaviors, so it’s up to each person and their healthcare provider to weigh the risks and benefits. Family members and caregivers should monitor for worsening symptoms or suicidal thoughts, especially during the first several months of treatment, and report any changes (Pfizer, 2018).  

Serotonin syndrome

Rarely, Pristiq may cause serotonin syndrome—a serious and potentially life-threatening condition that occurs when serotonin levels in the brain become too high. Taking Pristiq with other medications that also affect serotonin (such as other antidepressants and certain pain drugs) increases your risk. The symptoms of serotonin syndrome can progress quickly, so be sure to seek medical attention right away if you experience any of the following (Foong, 2018; Pfizer, 2018):

• Agitation or restlessness 

• Changes in blood pressure 

• Confusion 

• Diarrhea 

• Dizziness 

• Fast heartbeat 

• Fever 

• Flushing 

• Hallucinations 

• Muscle stiffness or muscle spasms 

• Nausea or vomiting 

• Nervousness 

• Seizures 

• Sweating 

• Tremor 

• Trouble sleeping 

• Trouble with balance or coordination 

Discontinuation syndrome 

You may experience withdrawal-type symptoms if you stop taking Pristiq—especially if you stop abruptly. Withdrawal symptoms generally start a few days after stopping Pristiq and can last for several weeks (Fava, 2018). If you’re interested in stopping Pristiq, speak with your healthcare provider first. They’ll likely develop a plan to decrease your dose slowly over time.  

Withdrawal symptoms may include (Pfizer, 2018): 

• Abnormal dreams

• Anxiety 

• Changes in your mood 

• Confusion 

• Diarrhea

• Dizziness 

• Electric shock sensations (paresthesia)

• Headache 

• Irritability or agitation 

• Nausea 

• Problems sleeping

• Ringing in your ears (tinnitus) 

• Seizures 

• Sweating 

• Tiredness

Bleeding risk 

Pristiq may increase your risk of bleeding, including nose bleeding, bruising, and bleeding in the stomach. Taking Pristiq with aspirin, NSAIDs (like ibuprofen or naproxen), or blood thinners increases this risk (Pfizer, 2018). 

Pregnancy and breastfeeding 

Let your healthcare provider know if you’re pregnant or plan to become pregnant before starting Pristiq. SNRIs like Pristiq are sometimes used during pregnancy, but risks do exist. Babies exposed to an SNRI during the third trimester of pregnancy may develop withdrawal-type reactions after delivery, including excessive crying, irritability, difficulty sleeping, and trouble feeding (Dubovicky, 2017). You and your healthcare provider will discuss the risks and benefits of starting or withholding treatment since untreated depression can also increase pregnancy complications. 

If you’re interested in breastfeeding your baby, talk with your healthcare provider about the risks. While Pristiq is present in breastmilk, a small study did not show any side effects in the babies (Pfizer, 2018). If your healthcare provider recommends you continue Pristiq while breastfeeding, monitor your baby for excessive sleepiness and adequate weight gain (LactMed, 2021).  

Other conditions

Some conditions may increase your risk of developing complications from Pristiq. Let your healthcare provider know if any of the following situations apply to you (Pfizer, 2018):

• Bleeding problems

• Heart problems 

• High blood pressure 

• High cholesterol 

• History of bipolar disorder, mania, or hypomania, or a family member with these conditions 

• History of seizures

• Kidney or liver problems

• Previous allergic reaction to desvenlafaxine (Pristiq) or venlafaxine (Effexor XR) 

• Previous stroke 

Pristiq may interact with certain medications. Always keep an updated list of all the medicines you take—including nonprescription, over-the-counter products—and share this information with your healthcare providers and pharmacist any time there are changes. 

Some medications should never be taken with Pristiq since they can increase the risk of serotonin syndrome. Never take Pristiq with (Pfizer, 2018):

• MAOIs (monoamine oxidase inhibitors): Don’t start Pristiq within 14 days of stopping an MAOI and don’t start an MAOI within seven days of stopping Pristiq. MAOIs include selegiline, tranylcypromine, isocarboxazid, and phenelzine. 

• Linezolid (Zyvox)

• Intravenous (IV) methylene blue 

Other drugs may increase your risk of serotonin syndrome if taken with Pristiq. They include (Foong, 2018):

• Other SNRIs like duloxetine (Cymbalta) and venlafaxine (Effexor XR) 

• SSRIs (selective serotonin reuptake inhibitors), such as paroxetine (Paxil), fluoxetine (Prozac), and sertraline (Zoloft)

• TCAs (tricyclic antidepressants) like clomipramine (Anafranil) and imipramine 

• Cough and cold products that contain dextromethorphan (“DM”) and chlorpheniramine 

• Natural health supplements like St. John’s wort, L-tryptophan, and diet pills 

• Drugs of abuse, such as ecstasy (MDMA), amphetamine, and cocaine 

Certain medications can increase the chance of bleeding with Pristiq. Let your healthcare provider know if you take (Pfizer, 2018):

• Aspirin 

• NSAIDs like ibuprofen or naproxen 

• Blood thinners like warfarin, apixaban (Eliquis), or rivaroxaban (Xarelto)

• Antiplatelet drugs like clopidogrel (Plavix) or ticagrelor (Brilinta) 

This is not a complete list of all the medications that may interact with Pristiq. Always talk to your healthcare provider before starting anything new. 

Depression doesn’t have to rule your life. Many of us find it difficult to admit when we need help, but taking care of your mental health is nothing to be ashamed of. Talk to your healthcare provider about all your symptoms and concerns. They may recommend Pristiq as one part of your treatment plan to get you back to feeling your best.

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Current version

October 12, 2021

Written by

Christina Varvatsis, PharmD

Fact checked by

Steve Silvestro, MD

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About the medical reviewer

Steve Silvestro, MD, Ro

Dr. Steve Silvestro is a board-certified pediatrician and Associate Director, Clinical Content & Education at Ro.