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Drug Side Effects of Effexor

author image Rae Uddin
Rae Uddin has worked as a freelance writer and editor since 2004. She specializes in scientific journalism and medical and technical writing. Her work has appeared in various online publications. Uddin earned her Master of Science in integrated biomedical sciences with an emphasis in molecular and cellular biochemistry from the University of Kentucky College of Medicine.
Drug Side Effects of Effexor
Pharmacist talking to woman about a prescription Photo Credit: Wavebreakmedia/iStock/Getty Images

Effexor (venlafaxine) is a prescription antidepressant medication indicated for the treatment of generalized anxiety disorder, depression, social anxiety disorder and panic disorder. This medication is a type of serotonin and norepinephrine reuptake inhibitor (SNRI) and works by increasing the amount of these mood-enhancing neurochemicals in the brain. Effexor is administered orally (capsule or extended-release capsule) and should only be taken as prescribed by your doctor. Be sure to discuss any concerns you may have regarding the drug side effects of Effexor with your doctor prior to beginning treatment.

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Stomach Upset

Certain patients may experience stomach-related side effects of Effexor during treatment. These can include nausea, vomiting or stomach pain. Burning or painful sensations in your chest or throat (heartburn) can also occur during Effexor treatment and may be accompanied by abdominal gas or burping. You can develop changes in your bowel habits and may begin to experience frequent episodes of diarrhea or constipation. Contact your doctor immediately if you notice blood in your stools or if you experience moderate to severe chest pain.

Dry Mouth

While receiving treatment with Effexor, you can develop dry mouth. If this occurs, you can also experience increased thirst or mild pain in your mouth or throat. Certain patients also develop changes in taste, which can cause foods to taste different or bland when you are eating.

Mood Alterations

Effexor can cause mood alterations in some people during treatment. You may frequently feel anxious or nervous, which may negatively impact your relationships or work or school obligations. Speak with your doctor immediately if you experience severe mood changes or if you begin to have troubling thoughts of self-harm or suicide.

Sleeping Difficulties

Treatment with Effexor can cause sleeping difficulties. During treatment, some patients can become abnormally fatigued or tired and can begin to yawn frequently. Other patients may have difficulty falling asleep or staying asleep through the night (insomnia), which can contribute to additional side effects of daytime sleepiness, fatigue, headache or weakness. Abnormal dreams or vivid nightmares can also occur due to Effexor, which may cause you to wake up frequently throughout the night. Such side effects can further contribute to side effects of tiredness and fatigue.

Weight Loss

While receiving treatment with Effexor you can develop a decreased appetite. If this occurs, you may begin to eat less frequently or eat smaller amounts of food. This can cause unintended weight loss.

Decreased Libido

Certain patients experience a decrease in sexual drive or desire (libido) as a side effect of Effexor treatment, explain health professionals at, a peer-reviewed drug product website. You may find it difficult to become aroused or orgasm normally. Such side effects can also have an impact on your intimate relationships.

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