What is the subcutaneous (SC) conversion of hydromorphone 0.25 mg orally (PO) every 6 to 8 hours?

Subcutaneous Conversion of Oral Hydromorphone

When converting hydromorphone 0.25 mg PO given every 6-8 hours to subcutaneous administration, the appropriate subcutaneous dose is 0.05 mg every 6-8 hours, based on a 5:1 oral-to-parenteral conversion ratio. 1, 2

Conversion Process

To convert from oral to subcutaneous hydromorphone, follow these steps:

1. Calculate total daily oral dose:

   • 0.25 mg PO × 3-4 times daily = 0.75-1 mg total daily oral dose

2. Apply conversion ratio:

   • Oral to parenteral (subcutaneous) conversion ratio for hydromorphone is 5:1 1, 2
   • 0.75-1 mg ÷ 5 = 0.15-0.2 mg total daily subcutaneous dose

3. Calculate individual subcutaneous dose:

   • 0.15-0.2 mg ÷ 3-4 doses = 0.05 mg subcutaneous dose every 6-8 hours

Evidence-Based Considerations

• The National Comprehensive Cancer Network (NCCN) guidelines recommend using a 5:1 oral-to-parenteral conversion ratio for hydromorphone 1
• Hydromorphone is approximately 5-7 times more potent than oral morphine 2
• For parenteral routes (IV and subcutaneous), hydromorphone is considered equipotent 1

Clinical Pearls and Pitfalls

• Start low, especially in:

  • Elderly patients
  • Opioid-naïve patients
  • Patients with renal dysfunction (hydromorphone-3-glucuronide can accumulate) 3

• Monitoring considerations:

  • Watch for signs of opioid toxicity including respiratory depression
  • Neurotoxicity (tremors, agitation) can occur even with low doses in patients with kidney dysfunction 3

• Dose adjustments:

  • When converting between opioids, consider reducing the calculated equianalgesic dose by 25-50% to account for incomplete cross-tolerance 1
  • For patients with inadequate pain control, titrate carefully by 25% increments 1

• Pharmacokinetic considerations:

  • Oral bioavailability of hydromorphone is low 4
  • Subcutaneous administration provides more consistent absorption than oral administration

This conversion ratio ensures appropriate analgesia while minimizing the risk of adverse effects when transitioning from oral to subcutaneous hydromorphone administration.