Venlafaxine (Effexor): dosage, uses, side effects

If you’ve been prescribed venlafaxine or Effexor XR for depression, anxiety, or panic attacks, you may have many questions about this medication. Learn about how venlafaxine works, common and serious side effects, what to look out for, and how to take it so you can start feeling better.

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Effexor is the brand name for venlafaxine, a type of antidepressant. This drug is available in the U.S. as Effexor XR, venlafaxine extended-release, and venlafaxine immediate release (see Important Safety Information). The Effexor brand is only available as Effexor XR. The extended-release capsule slowly dispenses venlafaxine for a convenient once-a-day dose. This drug is only available by prescription (NAMI, 2020).

Venlafaxine is approved by the U.S. Food and Drug Administration (FDA) to treat mental health conditions, including major depressive disorder (MDD), generalized anxiety disorder (GAD), social anxiety disorder, and panic disorder (Singh, 2020).

Venlafaxine may also be used off-label. This means using an FDA-approved drug for a use not formally approved by the FDA, a standard practice in medicine when a healthcare provider deems a medication to be the right treatment for a patient (FDA, nd).

Effexor XR and venlafaxine are used off-label to treat attention deficit disorder (ADD), migraine prevention, post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), complex pain syndromes, fibromyalgia, diabetic neuropathy, premenstrual dysphoric disorder (PMDD), and hot flashes in women who are going through menopause (Singh, 2020).

Venlafaxine is a serotonin-norepinephrine reuptake inhibitor (SNRI). Serotonin and norepinephrine are neurotransmitters or chemical messengers that affect the brain. These chemical messengers help to balance your mood. Low levels of serotonin and norepinephrine can lead to mental health conditions like anxiety, depression, and panic disorders (Singh, 2020).

This type of antidepressant does not create additional neurotransmitters. Instead, SNRIs work by slowing down the reabsorption of your natural neurotransmitters into specialized nervous system brain cells. This “delaying” action helps restore your brain’s chemical balance and improves your symptoms of depression or anxiety.

Effexor XR or venlafaxine do not work immediately. It may take six to eight weeks until you see an improvement in your mood (NAMI, 2020). 

Venlafaxine is not a short-term treatment. It does not cure your depressive symptoms; rather, it controls them. That means it’s important to keep taking your medication as prescribed to receive the full benefits of venlafaxine. Effexor XR and venlafaxine are considered safe and effective when taken as directed (NAMI, 2020).

Speak with your healthcare provider to see if venlafaxine or Effexor XR is right for you.

Like any medication, venlafaxine or Effexor XR can cause some side effects. Some common side effects happen when you first start taking this medication and gradually go away (NAMI, 2020).

Common side effects

Some of the most common side effects that generally do go away with time include (NAMI, 2020):

• Dizziness

• Dry mouth

• Gastrointestinal issues, such as nausea or constipation

• Loss of appetite

• Sweating

• Trouble sleeping

• Weakness

Some other common adverse effects you may be more likely to experience as long as you take the medication include (NAMI, 2020): 

• Erectile dysfunction

• Decreased libido

• High blood pressure

Speak to your healthcare provider about lowering your dose or changing your medication if these symptoms persist and disrupt your quality of life.

Serious side effects

Serious side effects are not common but can occur. If you experience any of these symptoms, call your healthcare provider immediately, especially if they worsen, call 911 (Wyeth Pharmaceuticals, 2018):

• Abnormal bleeding: This includes significant or frequent nosebleeds, coughing up blood, bruising easily and often, or blood in your stool.

• High blood pressure: Some signs of high blood pressure can include headaches or shortness of breath.

• Hyponatremia (low sodium levels): This can cause headaches, weakness, fainting, and seizures.

• Lung problems: These problems can cause pneumonia with chest pain, fever, cough, and shortness of breath.

• Serotonin syndrome: This is when your levels of serotonin are too high. You can have shakiness, fever, diarrhea, rapid heartbeat, anxiety, and seizures.

Some people may have an allergic reaction to venlafaxine. Mild allergic reaction symptoms include hives, itchiness, and redness. A severe allergic reaction has these life-threatening symptoms: swelling in your body, especially in your mouth, tongue, and throat, and trouble breathing. This is a medical emergency. Call 911 or head to the nearest emergency room if you experience these symptoms (Wyeth Pharmaceuticals, 2018). 

Effexor XR has a black box warning from the FDA (its most severe warning) for its potential to cause suicidal thoughts and behaviors in people under 24 years old.

This is not a complete list of side effects. Speak with your healthcare provider if you experience new or worsening symptoms. If you feel you need to stop taking Effexor due to side effects, speak with your healthcare provider first. Stopping Effexor XR suddenly can cause serious symptoms, so it’s important to wean off the medication slowly if need be. 

Your dose depends on any underlying medical issues, your mental health diagnosis, and how severe your condition is. Your healthcare provider will usually start you on a low dose and adjust it as needed. You need to communicate with your healthcare provider about your symptom improvement and any side effects you may be experiencing.

Venlafaxine and Effexor are available in the following dosages (Medscape, nd):

• Venlafaxine immediate-release tablets come in five strengths: 25 mg, 37.5 mg, 50 mg, 75 mg, and 100 mg. 

• Venlafaxine extended-release tablets come in four strengths: 37.5 mg, 75 mg, 150 mg, and 225 mg. 

• Effexor XR comes in three strengths: 37.5 mg, 75 mg, and 150 mg. 

Take venlafaxine and Effexor XR with food. Venlafaxine immediate-release tablets are typically taken two or three times a day. Venlafaxine extended-release tablets and Effexor XR capsules are usually taken once a day. You should take your antidepressant at the same time every day and as prescribed to you (Singh, 2020).  

Do not crush, split, or chew extended-release tablets or capsules. They need to be swallowed whole. 

What happens if I miss a dose?

You may want to set a reminder on your phone to take your medication. If you miss a dose, take it as soon as you remember. If it is close to the time of your next dose, only take your next dose. Do not take two doses at once. This raises the risk of serious side effects (Wyeth Pharmaceuticals, 2018).

Before your healthcare provider prescribes venlafaxine or Effexor XR, they will ask you about your medical and mental health history and the medications you currently take to determine if this medication will work best for you. 

Let your healthcare provider know if you have been diagnosed with bipolar disorder, angle-closure glaucoma, high cholesterol, high blood pressure, hyponatremia (low sodium in your blood), lung diseases, heart disease, stroke, tachycardia (rapid heart rate), kidney or liver disease, or a seizure disorder. Venlafaxine may increase the negative effects of these conditions (Wyeth Pharmaceuticals, 2018). 

Venlafaxine or Effexor XR can interact with certain medications, supplements, vitamins, and herbs. Some may increase the severity of the side effects or decrease the effectiveness of your antidepressant.

One of the more severe side effects is serotonin syndrome, which may occur if you take venlafaxine or Effexor XR with another medication that also increases serotonin levels in your body. When the neurotransmitter serotonin builds up in your body, it can cause agitation, anxiety, diarrhea, fever, hallucinations, rapid heartbeat, high or low blood pressure, vomiting, muscle rigidity, muscle twitching, and seizures. Call your healthcare provider immediately if you experience any of these symptoms (Wyeth Pharmaceuticals, 2018).

Medications you should not take with venlafaxine

If you take monoamine oxidase inhibitors (MAOIs) like isocarboxazid (Marplan), phenelzine (Nardil), selegiline (Eldepryl, Emsam, Zelapar), and tranylcypromine (Parnate), or if you have stopped taking one of these medications within the past 14 days, you should not take venlafaxine or Effexor XR. This combination can significantly increase your risk for serotonin syndrome. If you need to start taking an MAOI, you will typically need to wait at least one week after stopping venlafaxine (Wyeth Pharmaceuticals, 2018).

You also shouldn’t take Zyvox (linezolid) and methylene blue together with venlafaxine (Wyeth Pharmaceuticals, 2020).

Medications that interact with venlafaxine

Other types of medications also increase your risk of serotonin syndrome and other serious side effects. These include (Wyeth Pharmaceuticals, 2018): 

• Several selective-serotonin reuptake inhibitors (SSRIs), such as sertraline (Zoloft; see Important Safety Information) and fluoxetine (Prozac; see Important Safety Information)

• Other SNRIs like duloxetine (Cymbalta; see Important Safety Information)  

• Lithium, a medication to treat bipolar disorder

• Some stimulants, like Adderall XR

• Migraine medications called triptans

• Prescription pain relievers like Tramadol

• Fentanyl-based drugs

Some drug interactions can cause severe bleeding problems. These include taking venlafaxine or Effexor XR with prescribed anticoagulants or blood thinners like warfarin (Coumadin) or Xarelto. In addition, taking over-the-counter pain relievers like aspirin and non-steroidal anti-inflammatories (NSAIDs) like naproxen or ibuprofen (Advil or Motrin) together with venlafaxine can cause bleeding in your stomach (Wyeth Pharmaceuticals, 2018). 

Medications for weight loss like phentermine taken together with venlafaxine can cause excessive weight loss, high blood pressure, fast heart rate, and serotonin syndrome (Wyeth Pharmaceuticals, 2018).

Other interactions with venlafaxine

The supplements St. John’s wort, 5-HTP, and tryptophan can increase your risk for serotonin syndrome, especially if combined with venlafaxine (Wyeth Pharmaceuticals, 2018).

If you need to take a drug test for work or school, Effexor XR can cause a false positive result for phencyclidine (PCP), amphetamines, or methamphetamines (meth), even if you didn’t take any of these drugs. These false-positive results can occur up to a few days after you stop taking Effexor XR or venlafaxine (Singh, 2020).

Do not stop taking venlafaxine without speaking to your healthcare professional. If you abruptly stop taking venlafaxine, you may experience withdrawal symptoms. Some people may also have these symptoms when they adjust their venlafaxine dose downward. Your healthcare provider may gently taper the dose off to avoid withdrawal symptoms.

Withdrawal symptoms include anxiety, agitation, confusion, sleep problems, nausea, vomiting, diarrhea, tingling, numbness, electric shock-type feelings, and ringing in the ears. Additional symptoms include mania, irritability, lack of coordination, and depression (Wyeth Pharmaceuticals, 2018) 

Let your healthcare professional know if you experience these symptoms when decreasing or stopping this medication.

In rare cases, venlafaxine can cause fatal skin conditions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, and erythema multiforme (Wyeth Pharmaceuticals, 2018). 

Pregnant people should not take venlafaxine, especially in the last trimester. This is because venlafaxine may cause problems in your newborn baby. If you plan on breastfeeding your newborn, discuss your plans with your healthcare provider. There is a chance that this medication can be transferred via breast milk (Wyeth Pharmaceuticals, 2018). 

Have your eyes checked before taking venlafaxine. This medication can cause angle-closure glaucoma. This eye condition is caused by a blockage of eye fluids which increases eye pressure. This can result in a loss of vision. If you notice eye pain, swelling, or redness in or around your eye, changes in vision like seeing halos or rings around lights, or nausea, go to the nearest emergency room (Wyeth Pharmaceuticals, 2018).

If you are having any type of surgery, including dental surgery, let your surgeon know that you are taking venlafaxine (Wyeth Pharmaceuticals, 2018).

Venlafaxine, like other antidepressants, can cause sleepiness. Do not drive or use equipment that can harm you until you know how venlafaxine affects you. In the same vein, venlafaxine and alcohol interact with each other. Both have sedating qualities and can cause severe drowsiness (Wyeth Pharmaceuticals, 2018).

This is not a complete list of precautions with venlafaxine. Speak with your healthcare provider before starting this medication, and take it only as prescribed.

Antidepressants are one of the treatments that can help with your depression. Talk with your healthcare provider about the risks and benefits of venlafaxine. Venlafaxine is considered safe and effective when taken correctly. Working together with your healthcare provider, you can make the decision that works best for you to relieve your symptoms.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

July 12, 2021

Written by

Tobi Ash, MBA, RN, BSN

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.