Adverse effects of hydromorphone are similar to those of other opioid analgesics, such as morphine. The major hazards of hydromorphone include dose-related respiratory depression and sometimes circulatory depression. More common side effects include light-headedness, dizziness, sedation, constipation, nausea, vomiting, and sweating. Massive overdoses are rarely observed in opioid tolerant individuals, but when they occur they may lead to circulatory system collapse. A particular problem that may occur with hydromorphone is accidental administration instead of morphine due to a mix-up between the similar names, either at the time the prescription is written or when the drug is dispensed. This has led to several deaths and calls for hydromorphone to be distributed in distinctly different packaging to morphine to avoid confusion. The effects of overdose can be exaggerated by dose dumping if the medication is taken with alcohol or benzodiazepines.
A possible and likely side effect associated with hydromorphone is euphoria, achieved dually through a perceived effect from the transition of a state of pain to a state of pain-relief induced through opioids, or through direct stimulation of the μ opioid receptor (μ1 and μ2) [of which hydromorphone, related to the morphine molecule, is a primary μ agonist
