Hydromorphone (Dilaudid) is an opioid medication (powerful pain reliever) that's used to relieve pain when non-opioid medications don't provide enough pain relief. Depending on the form, it can be used to control sudden pain quickly or more long-lasting (chronic) pain. Taking hydromorphone (Dilaudid) for a long period of time can become habit-forming, and people can have bothersome symptoms if the medication is stopped suddenly.