Milnacipran affects certain chemicals in the brain called neurotransmitters. An abnormality in these chemicals is thought to be related to fibromyalgia. Milnacipran is not used to treat depression but how it works in the body is similar to how some antidepressants work. Milnacipran is used to treat a chronic pain disorder called fibromyalgia. Milnacipran may also be used for other purposes not listed in this medication guide.