Hydromorphone, also known as dihydromorphinone, and sold under the brand name Dilaudid among others, is an opioid used to treat moderate to severe pain. Typically, long-term use is only recommended for pain due to cancer. It may be used by mouth or by injection into a vein, muscle, or under the skin. Effects generally begin within half an hour and last for up to five hours. Common side effects include dizziness, sleepiness, nausea, itchiness, and constipation. Serious side effects may include abuse, low blood pressure, seizures, respiratory depression, and serotonin syndrome. Rapidly decreasing the dose may result in opioid withdrawal. Generally, use during pregnancy or breastfeeding is not recommended. Hydromorphone is believed to work by activating opioid receptors, mainly in the brain and spinal cord. Hydromorphone 2 mg IV is equivalent to approximately 10 mg morphine IV. Hydromorphone was patented in 1923. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2020, it was the 250th most commonly prescribed medication in the United States, with more than 1million prescriptions. Hydromorphone is made from morphine. Medical use Hydromorphone is used to treat moderate to severe pain. It may be used by mouth or by injection into a vein, muscle, or under the skin. Effects generally begin within half an hour and last for up to five hours. Typically, long-term use is only recommended for pain due to cancer. A 2016 Cochrane review (updated in 2021) found little difference in benefit between hydromorphone and other opioids for cancer pain. Side effects Adverse effects of hydromorphone are similar to those of other potent opioid analgesics, such as morphine and heroin. The major hazards of hydromorphone include dose-related respiratory depression, urinary retention, bronchospasm, and sometimes, circulatory depression. More common side effects include lightheadedness, dizziness, sedation, itching, constipation, nausea, vomiting, headache, perspiration, and hallucinations. These symptoms are common in ambulatory patients and in those not experiencing severe pain. Simultaneous use of hydromorphone with other opioids, muscle relaxants, tranquilizers, sedatives, and general anesthetics may cause a significant increase in respiratory depression, progressing to coma or death. Taking benzodiazepines (such as diazepam) in conjunction with hydromorphone may increase side effects such as dizziness and difficulty concentrating. If simultaneous use of these drugs is required, dose adjustment may be made. A particular problem that may occur with hydromorphone is accidental administration in place of morphine due to a