Elagolix has some common side effects like mood changes, insomnia, and nausea and is used to treat endometriosis which is when tissue grows outside the uterus and can cause pelvic pain and infertility.
Side effects of elagolix include menopausal-like symptoms such as hot flashes, night sweats, insomnia, amenorrhea, mood changes, anxiety, and decreased bone density, among others. Elagolix, sold under the brand name Orilissa, is a gonadotropin-releasing hormone antagonist (GnRH antagonist) medication which is used in the treatment of pain associated with endometriosis in women. Endometriosis is a condition in which cells similar to those in the endometrium, the layer of tissue that normally covers the inside of the uterus, grow outside the uterus. The main symptoms are pelvic pain and infertility. In endometriosis, there is a risk of associated female infertility of between 30% and 50%. The mechanisms by which endometriosis may cause infertility are not clearly understood, particularly when the extent of endometriosis is low. Nausea Common causes in include: endometriosis in women, bowel adhesions, irritable bowel syndrome, and interstitial cystitis. 
