Cymbalta: Brand name for duloxetine hydrochloride, a drug approved by the FDA to treat major depresssion in adults and to manage the pain associated with diabetic peripheral neuropathy, nerve damage in diabetes. The drug acts as a serotonin and norepinephrine reuptake inhibitor, increasing the levels of serotonin and norepinephrine, two neurotransmitters, or chemical messengers, believed to be important in regulating a person's emotions as well as reducing the sensitivity to pain.