Movantik (naloxegol) is a prescription medicine that blocks certain effects of narcotic medicines. An opioid is sometimes called a narcotic. Movantik is used to treat opioid induced constipation (OIC) caused by prescription pain medicines called narcotic or opiates, in adults with long-lasting (chronic) pain that is not caused by cancer. Naloxegol treats constipation without reducing the pain-relieving effects of the narcotic.