About 70% of morphine is used to make other opioids such as hydromorphone, oxycodone, heroin, and methadone. It is a Schedule II drug in the United States, Class A in the United Kingdom, and Schedule I in Canada.t can be used for both acute pain and chronic pain. Morphine is also frequently used for pain from myocardial infarction and during labour. It can be administered orally, intramuscularly, subcutaneously, intravenously, into the space around the spinal cord, or rectally.