What is the equivalent dose of hydromorphone (HM) subcutaneously (SQ) for a patient taking 90 units of Kadian (morphine sulfate) daily?

Hydromorphone Conversion for 90 mg Daily Kadian (Morphine Sulfate)

For a patient taking 90 mg of Kadian (morphine sulfate) daily, the equivalent subcutaneous hydromorphone dose is 12 mg daily, which can be administered as 0.5 mg every 2 hours or 1 mg every 4 hours. 1

Understanding the Conversion Process

Step 1: Determine the Morphine Equivalence Ratio

• According to clinical guidelines, hydromorphone is approximately 7.5 times more potent than oral morphine when administered orally 1
• For parenteral (subcutaneous) hydromorphone, the potency increases to approximately 3 times that of parenteral morphine 1, 2
• Parenteral morphine is approximately 3 times more potent than oral morphine 1

Step 2: Calculate the Equivalent Dose

1. Convert oral Kadian (morphine sulfate) 90 mg daily to parenteral morphine:

   • 90 mg oral morphine ÷ 3 = 30 mg parenteral morphine daily

2. Convert parenteral morphine to parenteral hydromorphone:

   • 30 mg parenteral morphine ÷ 2.5 = 12 mg parenteral hydromorphone daily

Step 3: Determine Dosing Schedule

• Subcutaneous hydromorphone can be administered:
  • 0.5 mg every 2 hours
  • 1 mg every 4 hours
  • 2 mg every 8 hours
  • Consider continuous infusion if frequent dosing is needed

Important Clinical Considerations

Individualization of Dosage

• The FDA label for hydromorphone emphasizes that dosage should be individualized based on:
  • Pain severity and frequency
  • Patient's medical status
  • Previous opioid exposure 2

Special Populations

• For elderly patients or those with hepatic or renal impairment, consider starting at a lower dose due to altered pharmacokinetics 2
• Patients with renal dysfunction may require dose adjustment as hydromorphone has active metabolites 3

Monitoring and Titration

• Monitor vital signs regularly, especially respiratory rate and oxygen saturation 3
• Titrate dose as needed based on pain control and side effects
• Be aware that oxygen desaturation can occur with IV hydromorphone, particularly with bolus dosing 4

Common Pitfalls to Avoid

1. Conversion Ratio Variations: Research suggests that the morphine-to-hydromorphone ratio may vary based on previous opioid exposure. Some studies suggest a ratio closer to 5:1 for morphine-to-hydromorphone conversion 5, 6, while the established guideline ratio is 7.5:1 1. Using the more conservative ratio (7.5:1) is safer to prevent overdosing.

2. Route of Administration: Always account for the change in bioavailability when converting between routes. The oral-to-parenteral conversion factor for hydromorphone is approximately 2.5:1 7.

3. Incomplete Cross-Tolerance: When rotating opioids, incomplete cross-tolerance may occur. Consider reducing the calculated equianalgesic dose by 25-50% when initiating the new opioid, then titrate to effect 1.

4. Monitoring Requirements: Subcutaneous administration requires regular monitoring of the injection site for irritation, inflammation, or infection.

By following these guidelines and carefully monitoring the patient's response, you can safely and effectively convert from oral Kadian to subcutaneous hydromorphone while maintaining adequate pain control.