What is the conversion dose from hydrocodone to morphine?

Hydrocodone to Morphine Conversion Dose

The standard conversion ratio is 1 mg of hydrocodone equals approximately 1 mg of oral morphine, making them essentially equianalgesic on a milligram-per-milligram basis.

Conversion Algorithm

When converting from hydrocodone to morphine, follow this structured approach:

Step 1: Calculate Total Daily Hydrocodone Dose

• Add up all hydrocodone doses taken in a 24-hour period 1
• For example, if a patient takes hydrocodone 10 mg four times daily, the total daily dose is 40 mg

Step 2: Apply the Conversion Ratio

• Use a 1:1 ratio as the baseline conversion (1 mg hydrocodone = 1 mg oral morphine) 2, 3
• For the example above, 40 mg hydrocodone daily would convert to approximately 40 mg morphine equivalent daily dose (MEDD)

Step 3: Reduce for Incomplete Cross-Tolerance

• Reduce the calculated morphine dose by 25-50% to account for incomplete cross-tolerance 4
• Using the example: 40 mg MEDD reduced by 25-50% = 20-30 mg morphine daily
• This reduction is critical to prevent overdosing when switching between opioids 4

Step 4: Divide Into Appropriate Dosing Schedule

• Divide the total daily morphine dose by the number of doses per day based on the formulation 4
• For immediate-release morphine given every 4 hours (6 doses/day): 20-30 mg ÷ 6 = 3.3-5 mg per dose
• For extended-release formulations, divide by 2 for twice-daily dosing

Critical Clinical Considerations

Breakthrough Pain Management

• Always prescribe breakthrough pain medication during the transition period 1
• Breakthrough doses should be 10-15% of the total daily morphine dose 1, 5
• Use short-acting opioids for breakthrough pain 1

Patient-Specific Adjustments

• Consider using 100% of the equianalgesic dose (no reduction) if pain was poorly controlled on hydrocodone 4
• Use the lower end of the dose reduction range (50% reduction) if switching due to side effects 4
• Adjust for age, renal function, hepatic function, and comorbidities 4

Important Caveats and Pitfalls

Avoid Fixed Ratios Without Clinical Judgment

• Do not apply conversion ratios rigidly without considering patient variability 4
• Significant variation exists in opioid conversion calculations across institutions and clinicians 2, 3
• The 1:1 hydrocodone-to-morphine ratio is approximate and should be adjusted based on clinical response 2

No Washout Period Required

• No washout period is needed when converting between pure opioid agonists like hydrocodone and morphine 4
• Begin the new opioid immediately after calculating the appropriate dose

Monitor Closely During Transition

• Reassess pain control and side effects frequently during the first 24-48 hours 1
• If breakthrough medication is required more than 3 times per day, increase the scheduled morphine dose 5
• Document pain scores and medication use to guide dose adjustments 5