What is the equianalgesic dose of IV Dilaudid (hydromorphone) for a patient taking 180 mg of methadone?

Equianalgesic Dose of IV Hydromorphone for 180 mg of Methadone

The equianalgesic dose of IV hydromorphone for a patient taking 180 mg of methadone is approximately 13.5 mg per day. 1

Conversion Process

Converting from methadone to another opioid requires special consideration due to methadone's unique pharmacokinetics and pharmacodynamics. The process involves multiple steps:

1. Convert methadone to morphine equivalent:

   • According to recent guidelines, 180 mg of oral methadone is equivalent to approximately 1,458 mg of oral morphine (using a conversion ratio of 1:8.1 for this dose range) 2

2. Convert oral morphine to IV hydromorphone:

   • Using the NCCN guidelines, we can determine that 10 mg IV morphine is equivalent to 1.5 mg IV hydromorphone 3
   • Therefore, 1,458 mg oral morphine ≈ 486 mg IV morphine (oral to IV morphine ratio of 3:1)
   • 486 mg IV morphine ÷ 10 × 1.5 = 72.9 mg IV hydromorphone

3. Apply dose reduction for cross-tolerance:

   • Reduce by 25-50% when converting between opioids to account for incomplete cross-tolerance 3
   • Using a conservative 50% reduction: 72.9 mg × 0.5 = 36.45 mg IV hydromorphone

4. Consider research-based conversion ratios:

   • Research specifically studying conversion from methadone to other opioids found a ratio of 1:13.5 for IV methadone to morphine equivalent daily dose 1
   • Using this direct ratio: 180 mg methadone × 13.5 ÷ 30 = 13.5 mg IV hydromorphone (using standard morphine to hydromorphone ratio of 30:1.5 or 20:1)

Important Clinical Considerations

• Start low and titrate: Begin with the lower calculated dose (13.5 mg/day) and titrate based on patient response
• Divided dosing: Administer the daily dose in divided doses every 2-3 hours as needed for pain 4
• Monitor closely: Methadone has a long half-life (8-59 hours), so its effects may persist for days after discontinuation 2
• Risk of respiratory depression: IV hydromorphone is potent and can cause significant respiratory depression, especially when initiating therapy 4, 5

Cautions and Pitfalls

• Avoid using standard conversion tables: Standard opioid conversion tables often overestimate the dose of IV hydromorphone needed when converting from methadone 6
• Patient variability: There is significant inter-patient variability in opioid response, so close monitoring is essential 4
• High-dose considerations: For patients on high doses of opioids (≥30 mg/day of IV hydromorphone equivalent), a lower conversion ratio may be needed 7
• Hepatic/renal impairment: Start with 25-50% of the calculated dose in patients with hepatic or renal impairment 4

Practical Administration

• Administer IV hydromorphone slowly, over at least 2-3 minutes 4
• Have rescue doses available during the transition period
• Monitor for signs of both overdose (sedation, respiratory depression) and withdrawal (anxiety, sweating, restlessness)
• Reassess frequently during the first 24-48 hours of conversion

This conversion is complex and requires careful clinical judgment, but the most evidence-based approach suggests using approximately 13.5 mg of IV hydromorphone per day as the equianalgesic dose for 180 mg of methadone.