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[Pharmacology](https://durgical.com/en/pharmacology/) · [Opioids and antagonists](https://durgical.com/en/pharmacology/classes/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

- Class: [Opioids and antagonists](https://durgical.com/en/pharmacology/classes/opioids-and-antagonists/)
- Receptor: μ-opioid receptor
- ATC code: N02AA03

## ⚠ High-alert medication

An error with this medicine can cause serious harm: double checks and protocols are used.

◎**μ-opioid receptor**Hydromorphone

ⓘ 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.

**Target in 3D:** μ-opioid receptor. PDB structure 8EF6 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/8EF6) · Drag to rotate · pinch to zoom

## 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

### Serious (rare, important)

- Life-threatening respiratory depression, above all at the start or after a dose increase
- Addiction, abuse and misuse, with risk of overdose and death
- Neonatal opioid withdrawal syndrome with prolonged use in pregnancy
- Adrenal insufficiency with prolonged use
- Severe hypotension
- Overdose from confusing the high-potency and standard formulations, or with other opioids

## 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.

## Memory aid

HYDROmorphone = morphine with «hyper» potency: the name looks alike, the dose does not. Always double-check.

## 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.

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## Related drugs

- [Morphine](https://durgical.com/en/pharmacology/morphine/)
- [Fentanyl](https://durgical.com/en/pharmacology/fentanyl/)
- [Naloxone](https://durgical.com/en/pharmacology/naloxone/)

[← Back to the class: Opioids and antagonists](https://durgical.com/en/pharmacology/classes/opioids-and-antagonists/)

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](https://medlineplus.gov/druginfo/meds/a682013.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [HYDROMORPHONE HYDROCHLORIDE injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e034eb96-03e0-46e1-8b92-5e1f94555e7b) (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](https://atcddd.fhi.no/atc_ddd_index/?code=N02AA03) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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