What is venlafaxine?
Venlafaxine is an antidepressant used to treat major depressive disorder, anxiety disorders, and panic disorder. It is a serotonin and norepinephrine reuptake inhibitor (SNRI), a class of drug that also includes desvenlafaxine, duloxetine, and levomilnacipran.
It works by altering levels of certain neurotransmitters, sometimes called the brain’s chemical messengers, which are involved in regulating aspects such as your mood, emotions, and appetite.
Venlafaxine comes in tablet or capsule form and can be regular-release or extended-release formulas. The regular-release formula was originally sold under the brand name Effexor and the extended-release formula as Effexor XR. While Effexor XR is still sold, the regular-release formula is now available as a generic drug and is no longer sold under the name Effexor.
What is venlafaxine HCl ER/XR?
Venlafaxine and venlafaxine HCl are the same drug; HCl stands for hydrochloride, which is an acid salt. Medications are often converted into hydrochlorides or other salts to improve their solubility in water, which quickens absorption into the bloodstream and improves their therapeutic effect.
HCl is often dropped from the name for convenience.
Venlafaxine ER refers to the extended-release formula, which is most commonly sold under the brand name Effexor XR.
What is venlafaxine used for?
Venlafaxine is approved by the FDA for treating major depressive disorder, generalized anxiety disorder, social anxiety disorder, and panic disorder.
Venlafaxine also has several off-label uses. Off-label use of drugs means it is used in a manner that is not approved by the FDA and is done so at a physician’s discretion based on their professional opinion.
Although SNRIs are not prescribed off-label as regularly as other antidepressants, venlafaxine is sometimes prescribed to treat hot flashes, migraines, obsessive-compulsive disorder, diabetic neuropathy, attention-deficit/hyperactivity disorder, and post-traumatic stress disorder.
How does venlafaxine work?
Venlafaxine belongs to a class of antidepressants called serotonin and norepinephrine reuptake inhibitors (SNRIs). SNRIs prevent the reuptake (or reabsorption) of two types of neurotransmitters, which increases their availability in the brain. Both types of neurotransmitters – serotonin and norepinephrine – are associated with mood and emotions.
Serotonin’s many roles in the body include helping regulate mood, social behavior, appetite, sleep, and memory. Low levels of serotonin have been linked to depression and anxiety. Venlafaxine prevents the reuptake (or reabsorption) or serotonin, increasing its availability in the brain, which is believed to alleviate the symptoms of depression and anxiety.
This is a similar mechanism of action to another class of antidepressants, called selective serotonin reuptake inhibitors (SSRIs). Common SSRIs include sertraline, citalopram, fluoxetine, and escitalopram.
The main difference between SSRIs and SNRIs, such as venlafaxine, is that the latter also prevents the reuptake of another type of neurotransmitter called norepinephrine.
Norepinephrine, also known as noradrenaline, is associated with regulating stress. As with serotonin, increasing levels of norepinephrine in your brain helps tackle the symptoms of depression and anxiety.
How long does venlafaxine stay in your system?
The elimination half-life of a drug refers to the time it takes for 50% of the drug to be eliminated from the body. With each subsequent half-life, a further 50% of the remaining drug is eliminated.
Regular-release venlafaxine has an average half-life of roughly five hours. It takes approximately 5.5 x the half-life of a drug for it to be cleared from your system, which would mean it takes just over a day (27 to 28 hours) for venlafaxine. However, the active metabolite of venlafaxine stays in your body for longer and continues to have an effect on your body.
When venlafaxine is metabolized in the body it results in a substance called O-desmethylvenlafaxine (ODV), which the drug’s only active metabolite (the word active means the substance continues to have an effect on the body, as opposed to inactive metabolites that do not). ODV is equally as potent as venlafaxine and has the same therapeutic effects.
The half-life of ODV is roughly 11 hours, meaning it takes two to three days to be cleared from your system.
Extended-release venlafaxine has an average half-life of around 15 hours, meaning it takes three to four days to be cleared from your system.
These times are averages; the time it takes for a drug to be eliminated from your body depends on various factors, including sex, age, and body weight.
How long does it take for venlafaxine to work?
Venlafaxine will usually start having an effect within the first few days, with symptoms such as inability to sleep, lack of energy, and lack of appetite gradually improving. It usually takes around six weeks for you to feel the full benefits of venlafaxine.
You should continue taking venlafaxine as prescribed, even if you do not notice an improvement in your symptoms immediately.
If you have not felt any (or much) improvement after around six weeks, or if side effects outweigh the benefits of venlafaxine, you should discuss alternative treatment options with your doctor.
Does venlafaxine cause suicidal thoughts and behavior?
Like other antidepressants, venlafaxine comes with an FDA black box warning about suicidal thoughts and behavior. Black box warnings are the strictest warnings issued by the FDA and are done so when there is significant evidence that a drug or product is associated with an adverse reaction that may lead to death or serious injury.
The full black box warning regarding suicidal thoughts and behaviors reads:
Antidepressants increased the risk of suicidal thoughts and behavior in children, adolescents, and young adults in short-term studies. These studies did not show an increase in the risk of suicidal thoughts and behavior with antidepressant use in patients over age 24; there was a reduction in risk with antidepressant use in patients aged 65 and older.
In patients of all ages who are started on antidepressant therapy, monitor closely for clinical worsening and emergence of suicidal thoughts and behaviors. Advise families and caregivers of the need for close observation and communication with the prescriber.
What are the side effects of venlafaxine?
Some common side effects of venlafaxine include:
- Bad taste in your mouth
- Loss of appetite
- Dry mouth
- Increased sweating
- Blurred vision
- Weight loss
- Loss of sexual desire/ability
These symptoms will often ease off or go away once your body adjusts to venlafaxine. You should speak to your doctor if any of these symptoms are particularly severe or persist/worsen over time. Venlafaxine can also raise your blood pressure, so your doctor may recommend tracking your blood pressure at home.
Venlafaxine can also cause more serious side effects. You should contact your doctor (or emergency services if you think your symptoms may be life-threatening or a medical emergency) immediately if the following side effects occur:
- Suicidal thoughts or thoughts of self-harm
- Chest pain
- Constant or severe headaches
- Easy bruising or bleeding or bleeding that is difficult to stop
- Muscle cramps, pain, or stiffness
- Shaking (tremors)
- Yellow skin or eyes
- Vomiting blood
- Unexplained or frequent bleeding from your gums
In rare cases, venlafaxine can lead to a potentially life-threatening condition called serotonin syndrome. This is a bigger risk when taken with certain other drugs or supplements (see question 9: Which other drugs interact with venlafaxine?). You should contact your doctor (or emergency services if you think your symptoms may be life-threatening or a medical emergency) immediately if you experience symptoms of serotonin syndrome, including:
- Muscle twitching
- Irritability or agitation
- Severe nausea, vomiting, or diarrhea
- Fast heartbeat
- Loss of coordination
Allergic reactions to venlafaxine are rare but can occur. Signs of a serious allergic reaction should be treated as a medical emergency. They include:
- Skin rash – for example itchy, red, or swollen skin
- Tightness in the chest or throat
- Trouble breathing or talking
- Swollen mouth, face, lips, tongue, or throat
This is not an extensive list of possible side effects of venlafaxine. For more information about side effects, please read the information leaflet that comes with the medication or speak to your doctor or pharmacist.
Which other drugs interact with venlafaxine?
There are many different drugs that can interact with venlafaxine.
One of the most serious interactions can cause a potentially life-threatening condition called serotonin syndrome (symptoms of which can be found in the above question: What are the side effects of venlafaxine?). A number of drugs and supplements can interact with venlafaxine and increase your risk of serotonin syndrome, including:
- Other antidepressants, including SSRIs (such as citalopram), tricyclics (such as amitriptyline), MAOIs (such as rasagiline), and atypical antidepressants (such as trazodone)
- Tripans (such as sumatriptan, used to treat migraine headaches)
- Drugs containing dextromethorphan (found in many over the counter cough and cold medications)
- St. John’s wort
This is not a comprehensive list of substances that can interact with venlafaxine and increase your risk of serotonin syndrome.
Other drugs that may interact with venlafaxine include:
- Several drugs used to treat cancer, including vemurafenib, vandetanib, osimertinib, ivosidenib, ceritinib, and cabozantinib
- Arsenic trioxide
Venlafaxine can interact with many more drugs and supplements than those listed here, some of which can increase the risk of serotonin syndrome. You should speak to your doctor about all prescription and over the counter medications you take, as well as supplements.
Can I drink alcohol while taking venlafaxine?
Alcohol can worsen some side effects of venlafaxine, including dizziness, drowsiness, and inability to concentrate.
It is usually recommended that you avoid drinking alcohol or limit how much you drink while taking venlafaxine, especially at the start of your treatment when you are most likely to experience side effects.
If you have any questions or concerns about drinking alcohol while on venlafaxine, you should discuss them with your doctor.
What painkillers can I take with venlafaxine?
If you need to take a painkiller while on venlafaxine, avoid aspirin or NSAIDs (non-steroidal anti-inflammatory drugs) such as ibuprofen and naproxen because they may lead to an increased risk of bleeding.
Paracetamol is generally safe to take together with venlafaxine.
Should I take venlafaxine with food?
Regular-release venlafaxine is usually taken two or three times per day with food, while extended-release is usually taken once per day – in the morning or evening – with food.
It is usually recommended that you take venlafaxine at the same time every day. You should discuss with your doctor the best way of taking venlafaxine and it is important to follow your doctor’s instructions carefully.
Is venlafaxine safe for pregnant women?
Animal studies have found that very high doses of venlafaxine can be harmful to developing fetuses. However, there are no adequate and well-controlled studies about venlafaxine’s effect on pregnancy in humans. Accordingly, the FDA classes venlafaxine as ‘category C’ regarding pregnancy, meaning it should only be taken by pregnant women if absolutely necessary and if the benefits outweigh the potential risk to the fetus. Otherwise, alternative treatment should be considered.
This mirrors the advice offered by the NHS in the UK.
Small amounts of venlafaxine and its active metabolite, ODV, have been found to pass into human breast milk. Your doctor should decide whether the benefits of venlafaxine outweigh the low risk of side effects to a nursing infant.
If you are breastfeeding while taking venlafaxine and notice your baby is not feeding well, is unusually sleepy, or you have any other concerns, you should speak to your doctor as soon as possible.
How do you wean off venlafaxine?
You should never suddenly stop taking venlafaxine or wean yourself off without speaking to your doctor.
If you want to stop taking venlafaxine, you should speak to your doctor about the safest way of doing so to minimize the risk of withdrawal symptoms. It can take two to six weeks or longer to wean off venlafaxine, depending on the dosage you’ve been taking and how your body responds to reducing your dosage.
Venlafaxine withdrawal symptoms can be serious, including:
- Brain shivers
- Electric shock-like sensations
- Weight gain
- Trouble sleeping
- Numbness or tingling in your hands or feet
How long can venlafaxine withdrawal last?
If you taper off venlafaxine under medical supervision, you may still experience withdrawal symptoms. However, they should be less severe and will typically disappear within a few weeks.
If you experience severe or persistent withdrawal symptoms, your doctor may reduce your dosage more slowly, giving your body more time to make gradual adjustments.
The content on this page is provided for informational purposes only. If you have any questions or concerns about your treatment, you should talk to your doctor, pharmacist, or healthcare professional. This is particularly important if you are taking multiple medications or have any existing medical conditions.