Drug interactions

Diamorphine + Ketamine

Severity: Major

Diamorphine and Ketamine: major interaction.

Last updated 29 Oct 2026 Sources: US FDA label

For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.

Summary

Diamorphine (heroin) is a potent opioid and ketamine can add to its sedative and respiratory depressant effects. The pair is used intentionally for analgesia but overdose risk rises.

Ketamine

What this interaction means in plain words

Diamorphine and Ketamine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.

Evidence level: Moderate

Why it happens

Additive CNS and respiratory depression via opioid receptor agonism and NMDA antagonism.

What to do

Use reduced doses and monitor respiratory rate, oxygen saturation and sedation closely. Keep naloxone and airway equipment available.

What to ask your pharmacist

Does the benefit of taking both outweigh the risk in my case?
Do I need any blood test, ECG or other check while on both?
What early warning signs should I watch for, and what should I do if they appear?

Bring a full list of your medicines, including over-the-counter products, supplements and herbal remedies, to every pharmacy visit.

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References

Ketalar - FDA drug label (DailyMed) - section 7 Drug Interactions (class statement: opioid analgesics; "Concomitant use of ketamine with opioid analgesics, benzodiazepines, or other central nervous system (CNS) depressants, including alcohol, may result in profoun") — DailyMed (FDA label)

Benzhydrocodone / acetaminophen + Ketamine Major
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Buprenorphine buccal + Ketamine Major
Buprenorphine long-acting + Ketamine Major
Buprenorphine subdermal implant + Ketamine Major
Buprenorphine transdermal + Ketamine Major

Frequently asked questions

Can I take Diamorphine with Ketamine?

MediHelp rates the interaction as major. Diamorphine and Ketamine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Diamorphine (heroin) is a potent opioid and ketamine can add to its sedative and respiratory depressant effects. The pair is used intentionally for analgesia but overdose risk rises.

How serious is the interaction between Diamorphine and Ketamine?

MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use reduced doses and monitor respiratory rate, oxygen saturation and sedation closely. Keep naloxone and airway equipment available.

What other medicines interact with Ketamine?

MediHelp also lists interactions of Ketamine with, for example, Benzhydrocodone / acetaminophen, Brexanolone, Buprenorphine buccal. The full list is on the Ketamine page.

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