Potency of Dilaudid (Hydromorphone) Compared to Morphine
Hydromorphone (Dilaudid) is approximately 5-7.5 times more potent than morphine when administered orally, and approximately 8.5 times more potent when administered intravenously. 1, 2
Potency Ratios by Route of Administration
Intravenous Administration
- Hydromorphone is 8.5 times more potent than morphine 2
- This means 1 mg of IV hydromorphone is equivalent to 8.5 mg of IV morphine
- Clinical guidelines recommend using hydromorphone at 0.015 mg/kg IV compared to morphine at 0.1 mg/kg IV, reflecting this potency difference 1
Oral Administration
- Hydromorphone is 5-7.5 times more potent than oral morphine 1
- According to the European Association for Palliative Care (EAPC), hydromorphone is "between 5 and 10 times as potent" as morphine 1
- The Annals of Oncology guidelines specifically list hydromorphone as 7.5 times more potent than oral morphine 1
Clinical Implications of Higher Potency
Advantages
- Smaller milligram doses are required for equivalent analgesia
- Clinicians may be more likely to adequately treat pain with 1.5 mg of hydromorphone versus 10 mg of morphine 1
- Hydromorphone has a quicker onset of action compared to morphine 1
- May cause less pruritus than morphine (0% vs 6% in one study) 3
Dosing Considerations
- Due to higher potency, careful dose calculation is essential when converting between these opioids
- For acute severe pain, hydromorphone at 0.015 mg/kg IV is comparable or potentially superior to morphine at 0.1 mg/kg IV 1, 3
- A 1 mg + 1 mg patient-driven protocol for hydromorphone is recommended over other IV opioids in emergency settings 1
Equianalgesic Conversion Factors
When converting between morphine and hydromorphone, use these approximate ratios:
- IV morphine to IV hydromorphone: 8.5:1
- Oral morphine to oral hydromorphone: 5-7.5:1
- Oral hydromorphone to oral morphine: 1:5-7.5
Important Clinical Caveats
- The potency ratio may vary slightly between patients due to individual factors
- Hydromorphone may have different cognitive and mood effects compared to morphine (potentially less cognitive impairment but improved mood) 4
- Both medications provide adequate analgesia with similar side effect profiles, with the exception of potentially less pruritus with hydromorphone 3, 4
- For patients with renal impairment, hydromorphone may be preferred over morphine due to fewer active metabolites 5
When switching between these opioids, start with the calculated equianalgesic dose but monitor closely and adjust as needed based on individual patient response.