Hydromorphone, also known as dihydromorphinone, and sold under the brand name Dilaudid, among others, is a centrally acting pain medication of the opioid class. It is made from morphine. Comparatively, hydromorphone is to morphine as hydrocodone is to codeine – it is a hydrogenated ketone thereof. In medical terms, it is an opioid analgesic, and in legal terms, a narcotic. Hydromorphone is commonly used in the hospital setting, mostly intravenously (IV) because its bioavailability is very low orally, rectally, and intranasally. Sublingual administration (under the tongue) is usually superior to swallowing for bioavailability and effects; however, hydromorphone is bitter and hydrophilic like most opiates, not lipophilic, so it is absorbed poorly and slowly through mouth membranes.