When to take pristiq?


Desvenlafaxine Succinate

Consumer Medicine Information

What is in this leaflet

This leaflet answers some common questions about Pristiq.

It does not contain all the available information. It does not take the place of talking to your doctor or pharmacist or asking questions.

All medicines have risks and benefits. Your doctor has weighed the risks of you taking Pristiq against the expected benefits it will have for you.

If you have any questions about Pristiq, ask your doctor or pharmacist.

Keep this leaflet with your Pristiq tablets. You may need to read it again.

What Pristiq is used for

What it does

Pristiq is used in the treatment and prevention of relapse of depression.

Depression can affect your whole body and may cause emotional and physical symptoms such as feeling low in spirit, being unable to enjoy life, poor appetite or overeating, disturbed sleep, loss of sex drive, lack of energy and feeling guilty over nothing.

Ask your doctor if you have any questions about why Pristiq has been prescribed for you. Your doctor may have prescribed it for another reason.

How it works

Pristiq contains the active ingredient called desvenlafaxine succinate. It belongs to a class of medications called Serotonin-Noradrenaline Reuptake Inhibitors (SNRIs).

Serotonin and noradrenaline are chemical messengers that allow certain nerves in the brain to work. Pristiq tablets increase the level of these two messengers. Experts think this is how it helps to restore your feeling of wellness.

Pristiq is not addictive.

It is available only with a doctor’s prescription.

Use in Children

The safety and effectiveness of Pristiq in children or adolescents under 18 years of age have not been established.

Before you take Pristiq

When you must not take it

Do not take Pristiq if you are taking other medications for depression known as monoamine oxidase inhibitors, even if you have stopped taking them, but have taken them within the last 14 days.

Do not take Pristiq if you are allergic to desvenlafaxine, venlafaxine or to any of the ingredients listed at the end of this leaflet.

Symptoms of an allergic reaction include:

  • Skin rash
  • Itching or hives on the skin
  • Swelling of the face, lips, tongue, throat or other parts of the body
  • Shortness of breath, wheezing, troubled breathing or difficulty swallowing.

Do not take this medicine after the expiry date (EXP) printed on the pack, or if the packaging is torn or shows signs of tampering. If it has expired or is damaged, return it to your pharmacist for disposal.

If you are not sure whether you should start taking this medicine, talk to your doctor.

Before you start to take it

Tell your doctor or pharmacist if you have allergies to any other medicines, foods, preservatives or dyes.

Tell your doctor or pharmacist if you are pregnant or intend to become pregnant. Pristiq is not recommended for use during pregnancy. Your doctor will discuss the risks and benefits of taking Pristiq if you are pregnant. One of these risks is that newborn babies whose mothers have been taking Pristiq may have several problems including breathing difficulties, rapid breathing, seizures, lack of oxygen in their blood, physical and / or behavioural problems, vomiting and diarrhoea.

If you take Pristiq or similar anti-depressants mid to late in your pregnancy, you may develop a condition known as “pre-eclampsia”, which is characterised by persistent high-blood pressure during or after pregnancy. Symptoms of pre-eclampsia can include headaches, abdominal pain, shortness of breath or burning behind the sternum, nausea and vomiting, confusion, heightened state of anxiety, and/or visual disturbances such as oversensitivity to light, blurred vision, or seeing flashing spots or auras.

If you take Pristiq or similar antidepressants in the last month of your pregnancy, you may experience heavy bleeding during and/or after delivery.

Continuing treatment with Pristiq or similar antidepressants during pregnancy should be strictly as directed by your doctor. Symptoms of a relapse may occur if treatment is discontinued, even if major depression was previously under control.

Tell your doctor or pharmacist if you are breast-feeding or plan to breast-feed. Pristiq passes into breast milk and there is a possibility that the breast-fed baby may be affected. For this reason, the use of Pristiq is not recommended in breast-feeding women.

Tell your doctor if you have, or have had, any medical conditions, especially the following:

  • A history of fits (seizures or convulsions)
  • A personal history or family history of bipolar disorder
  • Blood pressure problems
  • Glaucoma (increased pressure in the eye)
  • A tendency to bleed more than normal or you are taking a blood thinning medication
  • Raised cholesterol or lipid levels
  • Problems with your kidneys or liver
  • Problems with your heart
  • Low sodium levels in your blood
  • Any other medical conditions.

Tell your doctor if you plan to have surgery.

If you have not told your doctor about any of the above, tell them before you start to take Pristiq.

Taking other medicines

Tell your doctor or pharmacist if you take any other medicines, including:

  • all prescription medicines
  • all medicines, vitamins, herbal supplements or natural therapies you buy without a prescription from a pharmacy, supermarket, naturopath or health food shop, such as St John’s wort or tryptophan supplements.

Do not start to take any other medicine while you are taking Pristiq, unless it is prescribed or approved by your doctor.

Some medicines may interfere with Pristiq or Pristiq may interfere with these medicines. These include:

  • Medications for depression known as monoamine oxidase inhibitors (MAOIs) (such as moclobemide, phenelzine and tranylcypromine). Tell your doctor if you are taking or have stopped taking them within the last 14 days. Ask your doctor or pharmacist if you are unsure if you are taking any of these medicines. It is important that you do not take Pristiq or medicines similar to Pristiq with MAOIs or within 14 days of taking an MAOI as this may result in a serious life-threatening condition. Your doctor or pharmacist can tell you what to do if you are taking any of these medicines.
  • Any other medications for bipolar disorder, depression, anxiety, obsessive-compulsive disorder or pre-menstrual dysphoric disorder, including St John’s wort
  • Drugs that affect serotonin levels e.g. tramadol, dextromethorphan, fentanyl, methadone and pentazocine
  • Medicines used to treat Attention Deficit Hyperactivity Disorder (ADHD) such as dexamphetamine and lisdexamphetamine
  • Medicines for weight loss, including sibutramine
  • Triptans (used to treat migraine)
  • Linezolid (used to treat infections)
  • Drugs that affect your tendency to bleed e.g. Aspirin, NSAIDS, Warfarin.

You may need to take different amounts of your medicine, or you may need to take different medicines. Your doctor will advise you.

Your doctor or pharmacist has more information on medicines to be careful with or to avoid while taking Pristiq.

Switching to Pristiq from other antidepressants

Side effects from discontinuing antidepressant medication may occur if you are switched from other antidepressants, including venlafaxine, to Pristiq. Your doctor may gradually reduce the dose of your initial antidepressant medication to help reduce these side effects.

How to take Pristiq

Follow all directions given to you by your doctor or pharmacist carefully. They may differ from the information contained in this leaflet.

If you do not understand the instructions on the box, ask your doctor or pharmacist for help.

How to take it

Swallow the tablets whole with a glass of water or other non-alcoholic liquid.

Do not divide, crush, chew or place the tablets in water.

Do not be concerned if you see a tablet ‘shell’ in your faeces after taking Pristiq. As the tablet travels the length of your gastrointestinal tract, the active ingredient desvenlafaxine is slowly released. The tablet ‘shell’ remains undissolved and is eliminated in your faeces. Therefore, even though, you may see a tablet ‘shell’ in your faeces, your dose of desvenlafaxine has been absorbed.

How much to take

The usual dose is 50 mg taken once daily with or without food.

Do not change your dose unless your doctor tells you to. Your doctor will gradually increase your dose if needed.

If you have kidney problems, you may need a lower dose of Pristiq.

When to take it

Take Pristiq at approximately the same time each day. This could be either in the morning or in the evening.

Taking it at the same time each day will have the best effect. It will also help you remember when to take it.

How long to take it

Continue taking your medicine for as long as your doctor tells you.

Although you may begin to feel better after two weeks, it may take several weeks before you feel much better. It is important to give Pristiq time to work.

This medicine helps to control your condition, so it is important to keep taking your medicine even if you feel well.

If you forget to take it

If it is less than 12 hours until your next dose, skip the dose you missed and then take your next dose when you are meant to. Otherwise, take it as soon as you remember, and then go back to taking as you would normally.

Do not take a double dose to make up for the dose you missed. This may increase the chance of you getting an unwanted side effect.

If you are not sure what to do, ask your doctor or pharmacist.

If you have trouble remembering when to take your medicine, ask your pharmacist for some hints.

If you take too much (overdose)

Immediately telephone your doctor or the Poisons Information Centre (telephone: 13 11 26) for advice, or go to Accident and Emergency at your nearest hospital if you think that you or anyone else may have taken too much Pristiq.

Do this even if there are no signs of discomfort or poisoning. You may need urgent medical attention.

Keep the telephone number for these places handy whilst taking any medications.

While you are taking Pristiq

Things you must do

Visit your doctor regularly for a check up so that your progress can be checked. Always discuss any questions you have about Pristiq with your doctor.

Take Pristiq tablets as your doctor has prescribed.

Tell any other doctors, dentists and pharmacists who treat you that you are taking this medicine.

Keep enough Pristiq tablets to last weekends and holidays. This medicine helps to control your condition, but does not cure it. It is important to keep taking your medicine even if you feel well.

Watch carefully for signs that your depression is getting worse, especially in the first few weeks of treatment or if your dose has changed. Sometimes people with depression can experience a worsening of their depressive symptoms. This can happen even when taking an antidepressant.

Tell your doctor there is the potential for a false positive urinary drug screen while on Pristiq.

Tell your doctor immediately if you experience any of the following symptoms, especially if they are severe, you have not had these symptoms before or they happen very suddenly.

  • Anxiety or agitation
  • Panic attacks
  • Difficulty sleeping
  • Irritability
  • Aggressiveness
  • Hostility or impulsiveness
  • Restlessness
  • Overactivity or uninhibited behaviour
  • Other unusual changes in behaviour
  • Thoughts of suicide.

Tell your doctor immediately if you have any thoughts about suicide or doing harm to yourself.

Warning signs of suicide:

If you or someone you know is showing the following warning signs, contact your doctor or a mental health advisor right away or go to the nearest hospital for treatment.

All thoughts or talk about suicide or violence are serious.

  • Thoughts or talk about death or suicide
  • Thoughts or talk about self-harm or doing harm to others
  • Any recent attempts of self-harm
  • An increase in aggressive behaviour, irritability or agitation.

Things to be careful of

Be careful driving or operating dangerous machinery until you know how Pristiq affects you. Pristiq tablets may make you feel drowsy.

Things you must not do

Do not stop taking Pristiq or change the dose without the advice of your doctor, even if you feel better.

Your doctor may want to slowly decrease your dose of Pristiq to help avoid side effects. Side effects are known to occur when people stop taking Pristiq, especially when they suddenly stop therapy.

Some of these side effects include:

  • Headache
  • Nausea
  • Dizziness
  • Tiredness
  • Irritability
  • Anxiety
  • Abnormal dreams
  • Diarrhoea
  • Excessive sweating
  • Visual impairment
  • High blood pressure

Slowly reducing the amount of Pristiq being taken reduces the possibility of these effects occurring. In some people this may need to occur over periods of months or longer.

Some of these symptoms may impair driving, or the operation of dangerous machinery. Avoid these activities if you experience any of these symptoms.

Avoid drinking alcohol while you are taking Pristiq.

Do not give this medicine to anyone else even if they have the same condition as you.

Side effects

Tell your doctor or pharmacist as soon as possible if you do not feel well while you are taking Pristiq.

All medicines can have side effects. Sometimes they are serious; often they are not. You may need medical attention if you get some of the side effects.

It can be difficult to tell whether side effects are the result of taking this medicine, symptoms of your condition, or side effects of other medicines you may be taking. For this reason it is important to tell your doctor of any change in your condition.

Do not be alarmed by the list of side effects. You may not experience any of them.

Ask your doctor or pharmacist to answer any questions you may have.

Tell your doctor if…

Tell your doctor or pharmacist if you notice any of the following and they worry you:

  • Stomach, bowel or urinary tract problems:
    – Nausea or vomiting
    – Loss of appetite
    – Diarrhoea
    – Constipation
    – Difficulty passing urine
  • Changes in your behaviour:
    – Difficulty sleeping, abnormal sleepiness or abnormal dreams
    – Sexual function problems such as decreased sex drive, delayed ejaculation, problems achieving erection or difficulties achieving orgasm
    – Nervousness or anxiety
    – Feeling jittery or irritable
  • Difficulty thinking or working because of:
    – Yawning
    – Disturbances in concentration
    – Fainting or dizziness after standing up
    – Fatigue
    – Rapid heart beat
    – Chills
    – Headache
  • Excessive sweating
  • Hot flushes
  • Rash
  • Weight loss
  • Weight gain
  • Blurred vision
  • Ringing in the ears
  • Altered taste, dry mouth.

Tell your doctor as soon as possible if…

Tell your doctor as soon as possible if you notice any of the following:

  • Muscle spasms, stiffness, weakness or movement disorders
  • Abnormal facial movements such as tongue thrusting, repetitive chewing, jaw swinging, or grimacing
  • A feeling of apathy or not caring about things
  • Feeling detached from yourself
  • Hallucinations
  • Confusion
  • Agitation
  • Unusually overactive
  • Problems with breathing, shortness of breath
  • Bleeding or bruising more easily than normal
  • Numbness or pins and needles
  • Sensitivity to sunlight.

Go to hospital if…

Tell your doctor immediately, or go to Accident and Emergency at your nearest hospital if you notice any of the following:

  • Palpitations, shortness of breath, intense chest pain, or irregular heartbeats
  • Severe upper abdominal pain
  • Swollen and tender abdomen
  • Fever
  • Rise or decrease in blood pressure. You may experience headache, blurred vision, palpitations, confusion or loss of consciousness. Sometimes you may not experience any of these symptoms. It is important to keep your routine doctor’s appointments so that your blood pressure can be checked
  • Swelling of the face, lips, tongue, throat or other parts of the body
  • Seizures or fits
  • Symptoms of sudden fever with sweating, rapid heartbeat and muscle stiffness, which may lead to loss of consciousness.

Tell your doctor or pharmacist if you notice anything else that is making you feel unwell. Other side effects not listed above may also occur in some people. Some of these side effects (for example, increase in blood pressure, increase in blood cholesterol, changes to liver function, protein in the urine) can only be found when your doctor does tests from time to time to check your progress.

This is not a complete list of all possible side effects. Others may occur in some people and there may be some side effects not yet known.

Tell your doctor if you notice anything that is making you feel unwell.

After taking Pristiq


Keep your Pristiq tablets in their blister pack until it is time to take them. The tablets may not last as well if you take them out of the blister pack.

Keep Pristiq tablets in a cool dry place where the temperature stays below 25°C.

Do not store Pristiq tablets or any other medicine in the bathroom or near a sink. Do not leave Pristiq tablets in the car or on windowsills. Heat and dampness can destroy some medicines.

Keep Pristiq tablets and all medication where young children cannot reach it. A locked cupboard, at least one-and-a-half metres above the ground, is a good place to store medicines.


If your doctor tells you to stop taking this medicine or the expiry date has passed, ask your pharmacist what to do with any medicine that is left over.

Product Description

What Pristiq looks like

There are two strengths of Pristiq tablets:

Each blister pack contains 28 tablets.


Pristiq tablets contain 50 mg or 100 mg desvenlafaxine succinate as the active ingredient.

It also contains the following inactive ingredients:

  • Microcrystalline cellulose
  • Hypromellose
  • Purified talc
  • Magnesium stearate
  • Polyvinyl alcohol
  • Titanium dioxide
  • Macrogol
  • Iron oxide red
  • Iron oxide yellow (50 mg tablet only)
  • Sunset yellow FCF CI15985 (100 mg tablet only).

Pristiq does not contain gluten.


Pristiq tablets are supplied by:

Pfizer Australia Pty Ltd
Sydney, NSW
Toll Free Number 1800 675 229

Australian Registration Numbers:

Pristiq 50 mg tablets: – AUST R 170674

Pristiq 100 mg tablets: – AUST R 170696

Date of Preparation

This leaflet was last revised in September 2019.

® Registered Trademark.

© Pfizer Australia Pty Ltd 2018.

Published by MIMS November 2019

Pristiq vs Effexor: Main Differences and Similarities

Pristiq (desvenlafaxine) and Effexor (venlafaxine) are almost identical drugs that treat major depressive disorder. When Effexor is processed in the body, it breaks down into an active form of desvenlafaxine. Pristiq also contains an active form of desvenlafaxine. Both Pristiq and Effexor are considered serotonin and norepinephrine reuptake inhibitors (SNRIs). While some reports suggest advantages of one over the other, there is little overall difference between these drugs.


Pristiq is the brand name for desvenlafaxine extended-release tablets. It was FDA approved in 2008 to treat depression. Pristiq is an SNRI that works by blocking the reuptake of specific neurotransmitters called serotonin and norepinephrine. By blocking their reuptake, Pristiq increases the levels of these neurotransmitters to improve feelings of wellbeing and treat depression.

Pristiq is available as a 25 mg, 50 mg, and 100 mg extended-release oral tablet. The recommended dose is 50 mg once daily. In those with kidney problems, the dose is often decreased to reduce the risk of side effects. Pristiq should also be monitored and adjusted in those with liver problems.


Effexor is also known by its generic name, venlafaxine. However, it is usually prescribed as Effexor XR, the extended-release form of the medication. Effexor XR is an SNRI used to treat depression as well as some anxiety and panic disorders.

Effexor is available as a 37.5 mg, 75 mg, and 150 mg extended-release oral capsule. The dosage varies based on the condition being treated. The maximum dose is 75 mg or 225 mg per day depending on the condition. Like Pristiq, Effexor should be monitored in those with kidney and liver problems.

Pristiq vs Effexor Side by Side Comparison

Pristiq and Effexor are identical medications with many similarities. While they have many similarities, there are some slight differences between the two. These features can be found below.

Pristiq Effexor
Prescribed For
  • Major Depressive Disorder (MDD)
  • Major Depressive Disorder (MDD)
  • Generalized Anxiety Disorder (GAD)
  • Social Anxiety Disorder (SAD)
  • Panic Disorder
Drug Classification
  • Serotonin and norepinephrine reuptake inhibitor (SNRI)
  • Serotonin and norepinephrine reuptake inhibitor (SNRI)
  • Pfizer
  • Pfizer
Common Side Effects
  • Somnolence
  • Nausea
  • Dizziness
  • Constipation
  • Insomnia
  • Anxiety
  • Decreased appetite
  • Increased sweating
  • Erectile dysfunction
  • Somnolence
  • Nausea
  • Dry mouth
  • Erectile dysfunction
  • Decreased libido
  • Constipation
  • Decreased appetite
  • Increased sweating
Is there a generic?
  • Yes
  • Desvenlafaxine
  • Yes
  • Venlafaxine or Venlafaxine extended-release
Is it covered by insurance?
  • Varies according to your provider
  • Varies according to your provider
Dosage Forms
  • Oral capsule, extended release
  • Oral tablet
  • Oral capsule, extended release
Average Cash Price
  • $274 per 30 tablets
  • $544 per 30, 150 mg capsules
SingleCare Discount Price
  • Pristiq Price
  • Effexor Price
Drug Interactions
  • MAO inhibitors (isocarboxazid, phenelzine, selegiline, etc.)
  • Serotonergic drugs (fluoxetine, paroxetine, tramadol, trazodone, etc.)
  • Aspirin
  • NSAIDs
  • Warfarin
  • Alcohol
  • CNS drugs (phenobarbital, lorazepam, oxycodone, etc.)
  • MAO inhibitors (isocarboxazid, phenelzine, selegiline, etc.)
  • CYP2D6 inhibitors (paroxetine, fluoxetine, quinidine)
  • Serotonergic drugs (fluoxetine, paroxetine, tramadol, trazodone, etc.)
  • Aspirin
  • NSAIDs
  • Warfarin
  • Desipramine
  • Alcohol
  • CNS drugs (phenobarbital, lorazepam, oxycodone, etc.)
Can I use while planning pregnancy, pregnant, or breastfeeding?
  • Pristiq is in Pregnancy Category C. Animal studies have shown adverse effects to the fetus. Consult a doctor regarding steps to take while pregnant and breastfeeding.
  • Effexor is in Pregnancy Category C. Animal studies have shown adverse effects to the fetus. Consult a doctor regarding steps to take while pregnant and breastfeeding.


Pristiq (desvenlafaxine) and Effexor (venlafaxine) are two brand name medications that treat depression. As almost identical drugs, they are both grouped in a class of medications called SNRIs. Although they are both approved to treat depression, Effexor is also approved to treat anxiety and panic disorders.

Pristiq and Effexor are both available as extended-release oral tablets. However, they are metabolized in different ways. Pristiq is processed in the body by the CYP3A4 enzyme in the liver while Effexor is primarily processed by the CYP2D6 enzyme. Therefore, they may have slightly different drug interactions.

Both medications have similar side effects such as somnolence and sexual problems in some men. Although they are slightly different in dosing and metabolism, they essentially work the same way. Both medications are effective and may be prescribed depending on medical history and other personal factors.

The information here should be used as comparative info for two similar medications. All conditions and side effects should be discussed with a doctor. After a comprehensive review, Pristiq or Effexor may be determined as potential treatment options.

However, it’s a good idea to know what some of the sleep-related side effects are that have been reported with different types of drugs which act upon the brain. Let’s start with antidepressants. The most commonly prescribed ones are known as SSRIs (selective serotonin reuptake inhibitors) and have names including Prozac (fluoxetine), Zoloft (sertraline), and Paxil (paroxetine). Complaints of both insomnia and daytime sleepiness have been reported in patients with depression on SSRIs. Prozac’s impact on sleep has been the most widely studied. Interestingly, it has been shown to have both a sedating and energizing effect depending on the individual. Prozac can also cause decreased sleep efficiency, awakenings during the night, and interrupted REM (rapid eye movement) sleep, an important period during the sleep cycle that allows a person to dream vividly.

Antidepressants and Vivid Dreams

Another class of antidepressants, SNRIs (serotonin norepinephrine reuptake inhibitors), are known to cause sleep problems similar to those in SSRIs, as well as vivid dreams. Common SNRIs are Effexor (venlafaxine), Pristiq (desvenlafaxine) and Cymbalta (duloxetine).

Treatment with Effexor has also been associated with a condition known as dyskinesia that is characterized by occasional movement of one’s limbs, repetitive and involuntary movements of the extremities – typically the legs – usually during or just before falling asleep. There have also been cases where these involuntary movements have been seen a week after a person stopped taking Effexor.

One antidepressant, Wellbutrin (bupropion), has been associated with insomnia. However, studies that have examined electrical activity of the brain in patients taking bupropion indicate the drug actually increases REM sleep time.

It’s important to recognize whether the sleep problem you are having is a result of a side effect of a drug (or drugs) you are taking, or something completely independent of medication.

Antipsychotics are usually prescribed for schizophrenia and other psychotic disorders, though they are also prescribed for bipolar disorder and to supplement antidepressants in the treatment of depression. One of the most popular antipsychotics, Seroquel (quetiapine), has been associated with faster sleep onset and longer overall sleep time. A typical antipsychotic, Clozaril (clozapine) has also been associated with improving sleep onset and sleep time.

RLS (restless legs syndrome) can ruin a good night’s sleep and antipsychotics and antidepressants have been known to lead to cause it. The strong urge that RLS causes to uncontrollably move one’s legs can make it hard to sleep, lead to sleeplessness, irritability and depressed mood. Remeron (mirtazapine), an older, atypical antidepressant, is most likely to cause RLS. A case study found that RLS appeared to be provoked in patients on a low-dose of Seroquel. Interestingly, some evidence has shown that Wellbutrin may actually help to alleviate RLS.

Lifestyle Changes May Help Curb Sleep-Related Side Effects

However, you might find relief from RLS through lifestyle changes and/or taking certain vitamins. For example, going to the bed at the same time every night and getting up at the same time each morning can help. Also, there are some indications that a lack of some vitamins and minerals, such as iron, folic acid, magnesium, and vitamin B, can contribute to RLS.

Not surprisingly, insomnia and delayed sleep onset are associated with stimulants such as Adderall and Ritalin (methylphenidate), that are used in the treatment of ADHD. However, the effect of Ritalin on sleep may depend on the amount of time a child has been on the drug and when the medication is given. There have also been reports of children having difficulty falling asleep as they are being weaned off the medication.

Sleep is an important part of staying healthy and feeling good. Again, if you feel you are experiencing sleep issues as a result of medication, speak to your doctor without delay. Sleep-related side effects due to drugs impact relatively few patients. And if it ends up your sleep problems are not drug-related, the good news is there are steps you can take to rectify the situation. Changes in sleep hygiene and even in your bedroom environment can provide some of the most effective improvements, as can making sure you are getting enough sleep in the first place. As we are in the middle of Sleep Awareness Week, I recommend visiting the National Sleep Foundation’s website for more helpful tips.

This piece is based on an article, Adverse Effects of Psychotropic Medications on Sleep, published in the journal Psychiatric Clinics of North America in 2016.

Generic Name: desvenlafaxine (des VEN la FAX een)
Brand Names: Khedezla, Pristiq

Medically reviewed by Sophia Entringer, PharmD Last updated on Dec 1, 2019.

  • Overview
  • Side Effects
  • Dosage
  • Professional
  • Interactions
  • More

What is Pristiq?

Pristiq (desvenlafaxine) is an antidepressant belonging to a group of drugs called selective serotonin and norepinephrine reuptake inhibitors (SNRIs). Desvenlafaxine affects chemicals in the brain that may be unbalanced in people with depression.

Pristiq is used to treat major depressive disorder.

Pristiq may also be used for purposes not listed in this medication guide.

Important Information

Do not use Pristiq within 7 days before or 14 days after you have used an MAO inhibitor, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, or tranylcypromine.

Some young people have thoughts about suicide when first taking an antidepressant. Stay alert to changes in your mood or symptoms. Report any new or worsening symptoms to your doctor.

Do not stop using this medicine without first talking to your doctor.

Before taking this medicine

You should not take Pristiq if you are allergic to desvenlafaxine or venlafaxine (Effexor).

Do not use Pristiq within 7 days before or 14 days after you have used an MAO inhibitor, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, or tranylcypromine. A dangerous drug interaction could occur.

Some medicines can interact with desvenlafaxine and cause a serious condition called serotonin syndrome. Be sure your doctor knows if you also take stimulant medicine, opioid medicine, herbal products, or medicine for depression, mental illness, Parkinson’s disease, migraine headaches, serious infections, or prevention of nausea and vomiting. Ask your doctor before making any changes in how or when you take your medications.

Tell your doctor if you have ever had:

  • heart disease, high blood pressure, high cholesterol, or a stroke;

  • bipolar disorder (manic depression);

  • depression, suicidal thoughts;

  • liver or kidney disease;

  • glaucoma;

  • seizures or epilepsy;

  • lung or breathing problems;

  • a bleeding or blood clotting disorder; or

  • low levels of sodium in your blood.

Some young people have thoughts about suicide when first taking an antidepressant. Your doctor should check your progress at regular visits. Your family or other caregivers should also be alert to changes in your mood or symptoms.

Ask your doctor about taking Pristiq if you are pregnant. Taking an SNRI antidepressant during late pregnancy could increase your risk of excessive bleeding just after you give birth, and may cause serious medical complications in the baby. However, you may have a relapse of depression if you stop taking your antidepressant. Tell your doctor right away if you become pregnant. Do not start or stop taking Pristiq without your doctor’s advice.

If you are pregnant, your name may be listed on a pregnancy registry to track the effects of desvenlafaxine on the baby.

It may not be safe to breastfeed a baby while you are using this medicine. Ask your doctor about any risks.

Pristiq is not FDA-approved for use by anyone younger than 18 years old.

How should I take Pristiq?

Take Pristiq exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Take Pristiq with water at the same time each day, with or without food.

Swallow the tablet whole and do not crush, chew, or break it.

Your blood pressure will need to be checked regularly.

It may take several weeks before your symptoms improve. Do not stop using Pristiq without first talking to your doctor.

You may have unpleasant side effects if you stop taking this medicine suddenly. Follow your doctor’s instructions about tapering your dose.

Some tablets are made with a shell that is not absorbed or melted in the body. Part of the tablet shell may appear in your stool. This is a normal side effect and will not make the medicine less effective.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking Pristiq?

Avoid drinking alcohol.

Ask your doctor before taking a nonsteroidal anti-inflammatory drug (NSAID) for pain, arthritis, fever, or swelling. This includes aspirin, ibuprofen (Advil, Motrin), naproxen (Aleve), celecoxib (Celebrex), diclofenac, indomethacin, meloxicam, and others. Using an NSAID with desvenlafaxine may cause you to bruise or bleed easily.

Desvenlafaxine may impair your thinking or reactions. Avoid driving or hazardous activity until you know how this medicine will affect you.

Pristiq side effects

Get emergency medical help if you have signs of an allergic reaction to Pristiq: skin rash or hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), more depressed, or have thoughts about suicide or hurting yourself.

Call your doctor at once if you have:

  • a seizure (convulsions);

  • easy bruising or bleeding (nosebleeds, bleeding gums), blood in your urine or stools, coughing up blood;

  • blurred vision, eye pain or swelling, or seeing halos around lights;

  • cough, chest discomfort, trouble breathing; or

  • low levels of sodium in the body – headache, confusion, severe weakness, memory problems, feeling unsteady, hallucinations.

Seek medical attention right away if you have symptoms of serotonin syndrome, such as: agitation, hallucinations, fever, sweating, shivering, fast heart rate, muscle stiffness, twitching, loss of coordination, nausea, vomiting, or diarrhea.

Common Pristiq side effects may include:

  • dizziness, drowsiness, anxiety;

  • increased sweating;

  • nausea, decreased appetite, constipation;

  • sleep problems (insomnia); or

  • decreased sex drive, impotence, or difficulty having an orgasm.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Pristiq?

Taking Pristiq with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Many drugs (including some over-the-counter medicines and herbal products) can increase your risk of bleeding if you take them with Pristiq, especially:

  • a blood thinner such as warfarin, or other medicine used to prevents blood clots; or

  • an NSAID (nonsteroidal anti-inflammatory drug) – aspirin, ibuprofen (Advil, Motrin), naproxen (Aleve), celecoxib, diclofenac, indomethacin, meloxicam, and others.

This list is not complete and many other drugs may affect Pristiq. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Pristiq only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2020 Cerner Multum, Inc. Version: 9.01.

Medical Disclaimer

More about Pristiq (desvenlafaxine)

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  • During Pregnancy or Breastfeeding
  • Dosage Information
  • Drug Images
  • Drug Interactions
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  • Support Group
  • Pricing & Coupons
  • En Español
  • 795 Reviews
  • Generic Availability
  • Drug class: serotonin-norepinephrine reuptake inhibitors
  • FDA Approval History

Consumer resources

  • Pristiq
  • Pristiq (Advanced Reading)

Other brands: Khedezla

Professional resources

  • Pristiq (AHFS Monograph)
  • … +1 more

Related treatment guides

  • Major Depressive Disorder
  • Depression


First of all, it’s very important you understand that antidepressants are not “happy pills.” They’re not intended to block-out your pain or totally eliminate your difficult feelings. They’re designed to raise the floor of your depression, so that you’re able to get out of bed each morning, and (at least) function in your personal and professional domains. If you’re feeling depressed you should be engaging solid, responsible help (talk therapy) to assist you with issues that are contributing to your difficulties, so they can be resolved/healed. If you’re taking antidepressants alone or without doing inner work, it’s just like slapping a Bandaid on a deep, bleeding gash–and expecting it to heal. That’s just wishful thinking.

I am not a medical professional. This article is intended solely for your edification. Please do NOT contact me about your drug challenges or difficulties! Instead, make a list of your questions and/or troubling side effects, and have a dialogue with your prescribing physician about these concerns as soon as possible.

Benefits and side-effects from your antidepressants show up pretty quickly. Within a couple of days, you should be noticing how your body feels on that medication. This business of waiting “six weeks or more” before you notice any positive change, is utter nonsense! In my clinical experience, it simply isn’t true. Full benefit is cumulative–meaning it takes awhile for your body to absorb sufficient levels of the drug you’re on, to where you feel substantially better, but to presume that someone with acute clinical depression has to wait over a month to feel incremental improvements, is ludicrous.

I generally like to recommend that people ask their physician about starting out with a micro-dose of their antidepressant. A gradual initial introduction, say 2.5 to 5 mg’s of an SSRI as opposed to a standard beginning dose of 20 mg’s is a better way to ease a client into drug support with fewer side effects. I’m certain that no medical practitioner would sanction this approach, but many of my clients have had splendid results from following this protocol with their doctor’s permission, and some have continued indefinitely on a mini or ‘micro-dose’ without ever needing to increase their daily intake. When the client is monitored closely, maximum benefit can be achieved~ and in the arena of drug therapy, less is often more–unless of course, your physician is attending to acute or suicidal depression.

If you’re taking an SSRI and it makes you feel tired or drowsy, scroll down to the last several paragraphs of this article, where you’ll find ways to resolve this extremely common reaction! Do it now then come back~ because there are some important things you should learn about your meds here. Use this article only as a guideline (an information resource).

Your antidepressants should start to impact your depression within a few days to a week; if they don’t, speak with your doctor. If they make you feel more depressed or suicidal, you could be having a paradoxical response to this particular drug, and you should phone your physician immediately, and stop taking it! Generic versions of certain antidepressants can be more problematic in this regard, because some tend to be less stable in composition–so when beginning drug therapy, it’s really best to start with samples from your physician (if he/she doesn’t offer these, be sure and ask!) or buy the name brand. This will at least give you a frame of reference as to how effective a particular antidepressant can be for you, and whether a generic refill of your Rx might be sufficient for managing your symptoms. (A number of different companies manufacture generic drugs; your *drugstore chain* pharmacist cannot control the source of his/her supply month to month, which could have unfavorable consequences for you!)

Switching to a different drug is generally no problem, particularly if they’re in the same family (like with SSRI’s and SSNRI’s). Each Selective Serotonin Re-uptake Inhibitor has slightly different properties, in order to target adjacent symptoms like Obsessive Compulsive features (OCD) and/or anxiety issues. This is discussed further down within this text.

Each individual’s physical chemistry is somewhat unique; a medication that works well for your closest friend or sibling, may not be the optimal choice for you! If you’re not experiencing a favorable response to your initial drug trial or there are unpleasant side-effects, it could be that another within the same family, or a different type of antidepressant may yield better results.

Taking your antidepressants around the same time each day (or night) keeps this drug at consistent levels in your system, which is always a good idea; just make it part of your morning or evening ritual. Some folks find it easier to remember their pill(s) if they’re in the bathroom, next to their toothbrush. Find a place that’s convenient for you, and stick with it. If you oversleep one day or get thrown off schedule, don’t sweat it. Just try to take your dosage as close to the time you normally do, and you’ll be okay. If you accidentally miss a day, the sky won’t fall–but try to be very consistent with a daily routine when you’re starting out on psychopharmaceutical medication.

Depending on how long you’ve been taking them, most of these drugs have a half-life of a week or two. This means that the time it takes your body to rid itself of this drug (completely), could take up to about 14 days. Having a bad reaction to your first or second pill? You should be feeling much better in a day or so, after discontinuing it.

A very brief, manic/hyper or non-response to your drugs over a reasonable period (1 – 3 weeks) can indicate an atypical or non-specific Bipolar Disorder, that your physician may have overlooked during your initial psychiatric evaluation. Exploring this further (ruling out a bipolar issue) is critical to the success of your drug therapy! Bipolar Disorder generally requires that a mood stabilizer be combined with your antidepressant therapy. Mood stabilizers are different than antidepressants, as they are anti-convulsive drugs that are designed to control extreme mood shifts or swings.

Though not essential, it’s helpful if your talk therapist is somewhat familiar with various types of antidepressants, and can function as your advocate or go-between, with your prescribing physician. Your psychiatrist typically sees you for follow-up visits once every couple of months (or less often, once you’re stabilized), but your weekly clinician has a more direct sense of what you’re feeling, and should be alert to any side-effects; lethargy/fatigue, skin rashes, sleeplessness, sexual difficulties, stomach/intestinal problems, etc., that may be caused by the drug you’re taking. Based on much closer, more frequent monitoring, he/she should also be noting whether your current drug therapy is sufficient in helping you move through your crisis or difficulty. In my view, two heads are better than one, and a collaborative effort involving your doctor and therapist can significantly enhance your ability to mend.

While depression is almost never “just a chemical imbalance,” balancing brain chemistry can be a critically useful adjunct to your psychotherapeutic treatment. Depending on the nature and severity of your challenge or crisis, meaningful therapeutic intervention without the help of antidepressants can be like undergoing surgery without anesthetic!

Acute levels of pain make it tough for you to ‘hold’ therapeutic work, or make good use of it. Antidepressants can relieve some of the stress associated with psychic trauma, make it possible for you to move to the other side of a setback more effectively, and come out much stronger. While you may decide (instead) to rely on coping strategies you’ve used in the past, like alcohol/illicit drug use, overeating, over-work, shopping, getting a new pet or starting a romance to divert your pain, these can further complicate and compound your struggle! Frankly, no matter how tempting it seems, it’s best to resist these impulses if you’re hoping to make tangible and timely progress.

I’m frequently asked if antidepressants inhibit psychic abilities. While these medications can reduce/control psychosis, it has never been my experience that one’s psychic or clairvoyant capacity is diminished by these drugs.

You should be advised, that alcohol is a depressant. Drinking counteracts the benefits of any medications you’re taking to combat your discomfort, and undermines even the most solid therapeutic intervention! Aside from this, if you feel your current antidepressant therapy is insufficient for managing your symptoms, speak with your therapist and/or physician about switching to a different prescription, or increasing the one you’re taking. If your doctor seems unresponsive to your concerns or needs, find another doctor! OK, now with that out of the way . . .

These days, a lot of people on antidepressants are taking SSRI’s (Selective Serotonin Re-uptake Inhibitors), such as Zoloft, Celexa, Lexapro, Prozac or Paxil. Cymbalta (an SSNRI) is a newer member of this family that contains norepinephrine, and alleviates physical pain that can accompany depression. Cymbalta seems well tolerated by some people who’ve had difficulty with other SSRI’s, or found them to be less than effective.

A few of these meds (Celexa, Lexapro, Paxil) are formulated to target additional symptoms, like anxiety/panic and obsessive-compulsive tendencies. Paxyl is very hard to tolerate for many, due to its tendency to make patients very drowsy. Each SSRI has slightly different properties, so it might take a little experimenting to find out which is most effective for you. While a psychopharmacologist or psychiatrist may send you home with drug samples, your general practitioner/GP isn’t likely to have these on hand~ and he/she is seldom trained to prescribe psychotropic drugs or diagnose you properly! This means, you could end up with a cabinet full of costly prescriptions you can’t use, which isn’t just a nuisance–it deters your ability to recover. Drug manufacturers have cut back on free samples to Dr.’s since the inception of this article. What a bummer… sorry ’bout that!

Along these lines, I’ve seen many instances where folks are over-medicated (taking several drugs simultaneously that can counteract each other, and/or be superfluous)! This issue is frighteningly common among doctors who lack experience, or who are under-educated in the realm of psychopharmacology; too often, they’ll prescribe additional meds to relieve a patient’s unpleasant side-effects on a drug, rather than switching him or her to a different one. I personally believe that in the world of drug therapy, less is usually more. A medication that’s designed to target several of your symptoms, is healthier (and more economical) than taking several that haphazardly address each one. Add to this, various antidepressants like Effexor may be tolerated at lower doses, but lethargy/fatigue, intense sweating and other uncomfortable side-effects can manifest as dosage escalates. Increased intake problems can also occur with certain mood stabilizers (like Lamictal), used to treat Bipolar symptoms.

Drowsiness or tiredness can easily be experienced if your doctor has started you on an elevated dose of your antidepressant. In my view, the initial dosage on your SSRI should never be higher than 10 mg., to see how your body chemistry handles that drug. Combating fatigue on these drugs is addressed very shortly, but if your beginning dose is too high, you will feel like a zombie–no matter what time of day you’re taking it! Keep scrolling down, for more on SSRI fatigue!

Your psychiatrist may send you home with pharmaceutical sample packs that increase your daily dosage exponentially–which means that your body must immediately adapt to twice the amount of this medication in your system. Using a tablet cutter can help increase your dose more gradually, and save you from having to deal with any unpleasant side effects, as you adjust to a higher intake (make sure your doctor sanctions this). You should not try this with capsules, but your prescription might be available in more moderated doses, which will help you adapt to these changes more comfortably.

In light of these various considerations, it’s imperative you understand that your best outcome depends on solid pharmaceutical wisdom and responsible assessment. As with any professional domain, medical practitioners can vary widely in terms of experience, dedication and skill–but a thorough diagnosis of your symptoms is essential for determining your success with treatment.

Serotonin levels are raised over a period of time with use of these drugs, so while you could begin to feel a degree of relief within a few days, optimal effectiveness may take several weeks. SSRI’s and other antidepressants can cause dehydration, which leads to headaches, dry mouth, constipation and other related physical issues, so it’s important to drink plenty of water while taking them. The most common sexual side effects of SSRI’s, is they may inhibit libido and your ability to achieve orgasm, but individual results can vary significantly; I once had a client who’d taken Paxil years before we’d met, and reported a marked increase in his sex drive during the time he was on that drug. Naturally, this somewhat atypical response might be attributed in part, to relief from depressive symptoms.

If you’re not currently in a romantic or sexual relationship, it might be wise to attend to the more immediate need for relief from your depression, instead of worrying about the “what if’s” that may loom ahead. It’s just common sense.

SSRI’s are rarely tolerated by individuals who have irritable bowl syndrome (IBS) or a medical history that’s included other colon disturbances. In these instances, a cholinergic reaction (intense diarrhea) is very common, but your doctor should cover this during your intake session! Taking these meds with a little food rather than on an empty stomach, can decrease the incidence of nasty side-effects, like nausea.

The time of day you take your antidepressants can influence outcome; most prescriptions indicate morning dosage, but this can interfere with your ability to concentrate/focus or function well during your waking hours! All SSRI’s are formulated to raise and maintain serotonin levels in your brain tissue, which provides a soothing, relaxing, mood-elevating effect. The problem is, your productivity at work can be seriously compromised, if you’re taking them at the start of your day–particularly while you’re adjusting to them. While your depression should lift with the use of these drugs, if you take them in the morning, you could feel sleepy or lethargic afterward. This is pretty critical, because nobody feels good when they’re fatigued, unfocused and anxious about performing well at their job! In light of this, you might find yourself asking; “Is the prize worth this price I’m paying to feel better? And if not, do I throw the baby out with the bathwater–or make a simple adjustment?”

Frankly, I’m utterly mystified as to why doctors are still recommending their patients take SSRI’s in the morning, given these known, anticipated side-effects! While it’s true that certain antidepressants (such as Wellbutrin) are activating and must be taken during daytime hours, it’s certainly not true for most of them. Maybe pharmaceutical companies should become more aware of how you actually feel on their drugs, and give more specified guidelines to physicians prescribing them. Now that’s a novel idea, isn’t it?

This drowsiness issue is exacerbated if you’re struggling with symptoms of Attention Deficit Disorder (ADD/ADHD) in conjunction with your depression. Your SSRI can slow you down, but if you’re taking a stimulant for your ADD, it’s supposed to wake up your brain and activate you! It seems reasonable to presume that the properties of these two drugs (when taken at the same time) could counteract each other, to where you may not receive full benefit from either. In recent years, some physicians have found that adding small amounts of a stimulant drug to their patients’ antidepressant therapy had a synergistic effect; meaning, one enhanced the other’s effectiveness. Perhaps this practice was originally intended to mitigate the tranquilizing side-effects of these drugs–and (voila!) an inherent synergy between the two, was the unintended by-product. This appears to mean, that taking your SSRI around dinnertime (later, can leave you groggy the next morning) might enable you to sleep more soundly, and awaken more refreshed.

Various amphetamine-type stimulants can be very helpful if you have ADD, but WellbutrinXL is an activating antidepressant that’s often prescribed for attention deficit issues, and may better address your needs. This drug is fast acting, and has a short half-life (the time it takes to leave your body). Wellbutrin isn’t well-tolerated by everyone; some may experience irritability or even intense rage, and it might be better to start with a non time-release version, so unfavorable reactions can pass quickly. This drug might be worth trying–especially if your doctor can send you home with some samples. If you’re hyperactive with ADHD, you may have difficulty with Wellbutrin, as it can trigger anxiety, nervousness or irritability. Under these circumstances, Strattera or small amounts of an amphetamine like Ritalin or Adderall, may be a better option for you. Withdrawing from almost any prescription should be done gradually to avoid uncomfortable and/or dangerous side-effects. The exception, is when you have a paradoxical response (mentioned earlier) to a new Rx.

SSRI drugs often help one focus more easily, because we can relieve intense psychic/emotional pain, which drives obsessive-compulsive thinking, self-sabotaging behaviors and anxiety issues in many people. My experience with ADD and ADHD’ers is they do far better on a mini-dose of antidepressant than on a stimulant drug typically given to treat attention deficit problems.

I am not a physician, but I’ve worked closely enough with individuals taking psychopharmaceutical drugs, to have noticed a pattern of improvement after they’ve implemented a simple time shift in their antidepressant therapy. I strongly urge you to always check with your doctor about any concerns you have regarding your existing drug regimen or amending it, before initiating any changes. It’s perfectly acceptable to ask him/her about taking your SSRI in the evening, if you suspect this could provide a better night’s sleep, while enhancing your alertness, focus and motivation during daytime hours. Maybe it’s true that at least in this instance, “timing is everything.”


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