Description: Naldemedine, also known as S 297995, is a peripherally-selective μ-opioid receptor antagonist under development by Shionogi for the treatment of opioid-induced adverse effects including constipation, nausea, and vomiting. Clinical studies have thus far found it to possess statistically significant effectiveness for these indications and to be generally well-tolerated with predominantly mild to moderate gastrointestinal side effects. No effects indicative of central opioid withdrawal or impact on the analgesic or mydriatic effects of co-administered opioids have been observed.