Bipolar Disorder Treatment Medications Warnings and Precautions When Using Effexor (Venlafaxine) By Marcia Purse Marcia Purse is a mental health writer and bipolar disorder advocate who brings strong research skills and personal experiences to her writing. Learn about our editorial process Marcia Purse Medically reviewed by Medically reviewed by Steven Gans, MD on March 11, 2020 Steven Gans, MD is board-certified in psychiatry and is an active supervisor, teacher, and mentor at Massachusetts General Hospital. Learn about our Review Board Steven Gans, MD Updated on March 13, 2020 Print Radu Bighian / EyeEm / Getty Images Table of Contents View All Warnings Withdrawal Side Effects Precautions Other Facts Effexor (venlafaxine) is an antidepressant that is generally prescribed in an extended-release form as Effexor XR. Effexor is in a class of antidepressants called serotonin-norepinephrine reuptake inhibitors (SNRIs). Other categories of antidepressants include selective serotonin reuptake inhibitors (SSRIs) such as Prozac (fluoxetine) and Zoloft (sertraline), or tricyclic antidepressants such as Elavil (amitriptyline). Effexor appears to work by preventing your body from re-absorbing two different chemicals used to transmit nerve signals: serotonin and norepinephrine. These two neurotransmitters play an important role in determining a person's mood. The extended-release form of the drug, Effexor XR, is also prescribed for generalized anxiety disorder, panic disorder, and social anxiety disorder. Effexor Warnings One important thing to know before taking Effexor is that it must not be used in combination with another type of antidepressants called monoamine oxidase inhibitors (MAOIs) such as Nardil (phenelzine), Marplan (isocarboxazid), and Parnate. Serious and even fatal complications may result from such a combination. In addition, wait 14 days after discontinuing the MAOI drug before starting Effexor or Effexor XR, and wait at least seven days after discontinuing either form of Effexor before starting an MAOI. Withdrawal From Effexor It's best to start at a low dose of Effexor and build up to the desired strength gradually. Don't ever stop Effexor abruptly. A withdrawal syndrome, which may be severe, can occur even if the medication is tapered off, so be sure to work with your doctor if you need to go off of Effexor. Symptoms of withdrawal may include: Bizarre dreamsDizzinessGastrointestinal upsetHeadachesNauseaParesthesias (abnormal sensations of burning, prickling, tingling, etc.)Recurrence of depressionUnstable moods Effexor Side Effects Like any medication, side effects may occur while taking Effexor. Be sure to contact your doctor if they don't go away or become bothersome. Common side effects include: ConstipationDiarrheaDrowsinessFeeling tiredHeadacheHeartburnLoss of appetiteNauseaSexual side effectsVomiting Other Precautions Make sure your doctor knows your complete medical history. Effexor may need to be used with caution if you have: Brain disease or damage, or a history of seizures: The risk of seizures may be increased when taking Effexor.Heart disease or high or low blood pressure: Effexor may occasionally make these conditions worse.History of mania: The risk of developing mania may be increased while taking Effexor. Obviously, this is very important for bipolar patients to watch for.Kidney disease or liver disease: Higher blood levels of Effexor may occur, increasing the chance of side effects. Your doctor may need to adjust your dose. Other Important Facts These facts may be important to be aware of if you're taking or plan to take Effexor. It may take several weeks for the full effects of this medication to kick in. You should always take Effexor as directed, generally with food, and do not break, crush or chew tablets or open the capsules. If you miss a dose, do not take a double dose to make up. Be cautious and let your doctor know when taking any over-the-counter medications with Effexor or Effexor XR. Nausea is the most commonly reported side effect. This will usually diminish within 2 weeks. Animal test results show that the use of Effexor while pregnant or nursing may not be wise. Talk to your doctor about weighing the risks versus the benefits. Effexor and Effexor XR may cause weight loss. This weight loss is usually small. Talk to your doctor about this if you're concerned or if you start losing too much weight. Alcohol can increase the feeling of drowsiness this medication may cause. Was this page helpful? Thanks for your feedback! Dealing with racing thoughts? Always feeling tired? Our guide offers strategies to help you or your loved one live better with bipolar disorder. Sign up for our newsletter and get it free. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Shelton RC. Serotonin and Norepinephrine Reuptake Inhibitors. Handb Exp Pharmacol. 2019;250:145-180. doi:10.1007/164_2018_164 U.S. Food and Drug Administration. Effexor XR (venlafaxine Extended-Release) Capsules. Updated 2017. U.S. Food and Drug Administration. Effexor. Updated 2006. Ye C, Ninneman M, Christian JS, Zhang F, Musselman D. Seizure Induced by a Therapeutic Dose of Venlafaxine ER: A Case Report. J Psychiatr Pract. 2018;24(2):117-120. doi:10.1097/PRA.0000000000000298 Patel R, Reiss P, Shetty H, et al. Do antidepressants increase the risk of mania and bipolar disorder in people with depression? A retrospective electronic case register cohort study. BMJ Open. 2015;5(12):e008341. doi:10.1136/bmjopen-2015-008341 Additional Reading "Venlafaxine." MedLine Plus, U.S. National Library of Medicine (2014).