Drug Interaction Report

Dihydrocodeine and Hydromorphone Injection: Interaction Details

A pharmacist-reviewed analysis of the Dihydrocodeine and Hydromorphone Injection interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Dihydrocodeine

No brand names on record
+

Hydromorphone Injection

Dilaudid Dilaudid-HP® Dilaudid®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
How we grade severity & evidence

Severity levels

  • Contraindicated: These should generally not be used together.
  • Major: Potentially serious — often needs a change or close monitoring.
  • Moderate: Can be significant — usually manageable with monitoring.
  • Minor: Usually limited clinical impact.

Evidence grades

  • Established: Well documented — supported by controlled studies or strong clinical data.
  • Probable: Good supporting evidence, though not definitively proven.
  • Suspected: Some evidence suggests this interaction, but it is not well established.
  • Possible: Limited or conflicting evidence; the interaction may occur.
  • Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.

Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.

Of 54 documented Dihydrocodeine interactions, 51 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
unspecified
Evidence
theoretical
Severity
Major

What happens

Increased risk of respiratory and CNS depression and an increased risk of serotonin syndrome

Interaction Deep Dive

Concomitant use of dihydrocodeine with CNS depressants can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death. Reserve the concomitant use of dihydrocodeine and CNS depressants to patients for whom alternatives are inadequate. If concomitant use is necessary, use the lowest dose and shortest duration necessary to achieve treatment goals. Consider using a lower dose of dihydrocodeine or the CNS depressant and closely monitor for sedation, respiratory depression, and signs and symptoms of serotonin syndrome1. Inform patients and caregivers of this potential interaction and educate them on the signs and symptoms of respiratory depression (including sedation). If concomitant use is warranted, consider prescribing naloxone for the emergency treatment of opioid overdose 2.

Why it happens (mechanism)

Additive CNS depression; additive serotonergic effects

Literature reports

2 reports — tap to read

a) Observational studies have demonstrated that concomitant use of opioid analgesics and benzodiazepines increases the risk of drug-related mortality compared to use of opioid analgesics alone. Because of similar pharmacological properties, it is reasonable to expect similar risk with the concomitant use of other CNS depressant drugs with opioid analgesics 2.

b) Cases of serotonin syndrome, a potentially life-threatening condition, have been reported during concomitant use of opioids with serotonergic drugs 2.

Common questions

Can I take Dihydrocodeine and Hydromorphone Injection together?

Increased risk of respiratory and CNS depression and an increased risk of serotonin syndrome Always confirm with your pharmacist or prescriber before making any change.

How serious is the Dihydrocodeine and Hydromorphone Injection interaction?

It is rated major. Potentially serious — often needs a change or close monitoring.

How quickly could this interaction happen?

The documented onset is "unspecified". The timing of this interaction is not well characterized.

How strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

  • Does my dose of Dihydrocodeine or Hydromorphone Injection need adjusting while I take them together?
  • What symptoms should prompt me to call you or my prescriber right away?
  • Does the timing of my doses matter for this combination?
  • Is there a safer alternative to one of these medications for me?

References (2)

  1. Product Information: TREZIX(TM) oral capsules, acetaminophen caffeine dihydrocodeine bitartrate oral capsules. WraSer Pharmaceuticals (per DailyMed), Ridgeland, MS, 2016. DailyMed
  2. Product Information: SYNALGOS(R)-DC oral capsules, aspirin, caffeine, dihydrocodeine bitartrate oral capsules. Sun Pharmaceuticals Industries Inc (per FDA), Cranbury, NJ, 2023. DailyMed
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Dihydrocodeine

Keep reading about Dihydrocodeine

All Dihydrocodeine interactions (54)
Also serious with: Linezolid Injection Clopidogrel Cyclosporine Ophthalmic Furosemide Injection
Hydromorphone Injection

Keep reading about Hydromorphone Injection

All Hydromorphone Injection interactions (344) Hydromorphone Injection drug information
Also serious with: Isocarboxazid Naltrexone Phenelzine Safinamide

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