Hydromorphone: pharmacology and clinical applications in cancer patients.

Hydromorphone is a more potent opioid analgesic than morphine and is used for moderate to severe pain. It can be administered by injection, by infusion, by mouth, and rectally. Oral bioavailability is low. The kidney excretes hydromorphone and its metabolites. Some metabolites may have greater analgesic activity than hydromorphone itself but are unlikely to contribute to the pharmacological activity of hydromorphone. With the exception of pruritus, sedation and nausea and vomiting, which may occur less after hydromorphone than after morphine, the side-effects of these drugs are similar. On a milligram basis hydromorphone is five times as potent as morphine when given by the oral route, and 8.5 times as potent as morphine when given intravenously.