Pharmacology · Opioids and antagonists
Hydromorphone !
A μ-opioid agonist several times more potent than morphine, for severe pain. Mix-ups between its strengths, or with morphine, have caused deaths.
Updated 2026-11-01
The figure shows morphine in the μ receptor; hydromorphone, a ketone derivative of morphine, occupies the same site. There is no structure of hydromorphone in the receptor.
Mechanism of action
Hydromorphone is a full μ-receptor agonist, a semi-synthetic derivative of morphine and more potent than it. It activates the Gi protein, closes presynaptic calcium channels and opens potassium channels, reducing pain transmission; in the brainstem it reduces the drive to breathe.
- Binds the μ receptor with more potency than morphine
- The Gi protein closes Ca²⁺ channels and opens K⁺ channels
- Less neurotransmission in the pain pathway
- Strong pain relief; respiratory depression if the dose is excessive
Pharmacokinetics
- Metabolism
- Liver, almost all by glucuronidation to hydromorphone-3-glucuronide.
- Elimination
- Kidney; in renal or hepatic impairment treatment starts with lower doses.
Indications
- Severe pain needing an opioid, including postoperative and cancer pain
Adverse effects
Common
- Dizziness, lightheadedness and sedation
- Nausea and vomiting
- Sweating and flushing
- Dry mouth and itching
- Constipation
Contraindications
- Significant respiratory depression
- Acute or severe bronchial asthma without monitoring or resuscitation equipment
- Known or suspected gastrointestinal obstruction, including paralytic ileus
- Hypersensitivity to the drug
Key interactions
- Benzodiazepines, alcohol and other central nervous system depressants
- Add up to profound sedation, respiratory depression, coma and death.
- Naloxone
- Reverses its effects and can precipitate withdrawal in dependent patients.
What is monitored
- Respiratory rate, oxygen saturation and sedation level
- Blood pressure
- Bowel habits
- Kidney and liver function
Administration and safety
- The high-potency formulation is only for opioid-tolerant patients; confusing it with the standard one can be fatal.
- Hydromorphone and morphine have similar names and very different potencies: name and concentration are checked with an independent double check.
- It can be given intravenously, intramuscularly or subcutaneously; intravenous doses are given slowly.
- Controlled medicine: the order is verified, every dose recorded and leftovers kept secure.
Nursing care
- Before each dose: respiratory rate, oxygen saturation and sedation level; hold the dose and report excessive sedation or slow breathing.
- Keep naloxone at hand and teach the family to recognise an overdose.
- Prevent constipation from the start and track bowel habits.
- Prevent falls: dizziness, drowsiness and orthostatic hypotension.
- Teach the patient to lock the medicine away and dispose of leftovers safely.
Pregnancy and breastfeeding
Prolonged use in pregnancy can cause neonatal opioid withdrawal syndrome, which is expected and treatable; the newborn is watched after birth.
Test yourself
Think of the answer, then tap the question to see it.
Why is hydromorphone a high-risk medicine for errors?
It is much more potent than morphine, has a similar name and comes in a high-potency formulation; mix-ups can cause fatal overdose.
Which patients may receive the high-potency formulation of hydromorphone?
Only those who are already opioid-tolerant.
What is checked before each dose of hydromorphone?
Respiratory rate, oxygen saturation and sedation level, because respiratory depression is its gravest risk.
Related drugs
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Hydromorphone: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); HYDROMORPHONE HYDROCHLORIDE injection, solution (DailyMed (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 23 (McGraw Hill, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.