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The Negative Side Effects of Cymbalta

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.
The Negative Side Effects of Cymbalta
After you take a dose of Cymbalta, you may feel abnormally tired or drowsy as a side effect of treatment.

Cymbalta (duloxetine) is a prescription medication indicated for the treatment of generalized anxiety disorder, depression, fibromyalgia and diabetic nerve pain. This medication is part of a class of drugs called selective serotonin and norepinephrine reuptake inhibitors, which act by increasing the levels of these chemicals within the brain. Discuss the negative side effects of Cymbalta with your doctor before beginning treatment.

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The most common negative side effect of Cymbalta is nausea. In clinical trial data provided by the U.S. Food and Drug Administration (FDA), approximately 25 percent of Cymbalta-treated patients experienced nausea. In comparison, only 9 percent of placebo-treated (sugar pill-treated) patients reported similar side effects. Nausea can be uncomfortable and may become worse during motion-related activities, such as walking or riding in a vehicle. Cymbalta can also cause certain patients to experience dry mouth or a decreased appetite during treatment, which can lead to weight changes in some patients. To limit the occurrence of stomach-related side effects, your doctor may recommend that you take Cymbalta after eating a small meal or snack.


During treatment with Cymbalta, you can experience constipation, which can make it difficult for you to produce a bowel movement. An estimated 11 percent of patients taking this medication in clinical trials reported constipation as a side effect of treatment. Only 4 percent of patients taking placebo reported experiencing similar side effects, explains the FDA. Symptoms of constipation can contribute to nausea and may be accompanied by stomach bloating, cramping or pain.


After you take a dose of Cymbalta, you may feel abnormally tired or drowsy as a side effect of treatment. Certain patients also experience dizziness, weakness or blurred vision in conjunction with drowsiness. Such side effects can negatively impact your ability to remain attentive and alert while driving or participating in work- or school-related activities. Side effects of severe fatigue, weakness, tiredness or fainting during Cymbalta treatment should be immediately reported to your doctor.

Increased Sweating

You can experience excessive sweating--especially at night--while receiving treatment with Cymbalta. Increased perspiration can cause your bed sheets or clothing to feel damp when you wake up in the morning. You may also find that night sweats cause you to wake up frequently throughout the night, which can contribute to side effects of drowsiness or fatigue.

Suicidal Thoughts

Patients under the age of 24 who take antidepressants such as Cymbalta are at an increased risk of experiencing suicidal thoughts during treatment. Contact your child’s pediatrician or doctor immediately if you notice unusual changes in your child’s behavior, such as increased depression, panic or aggression, or if he begins to think about harming or killing himself.

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