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Use of Cymbalta (duloxetine) or serotonin norepinephrine reuptake inhibitor (SNRI) antidepressants can elevate Prolactin levels resulting in hyperprolactinemia, galactorrhea, non-menstrual vaginal spotting etc. The symptoms that you are experiencing could be related to Cymbalta use. You can consider requesting your treating doctor to change you to alternative medicines for better symptom control. Be in regular follow-up and monitoring of your treating doctor and gynecologist.
Take care.