Opioid Conversion from Tylenol #3 to Hydromorphone Contin
Direct Conversion Recommendation
For a patient taking 8 Tylenol #3 tablets daily (240 mg codeine/day), convert to approximately 6-9 mg oral hydromorphone daily, divided into 2 doses of Hydro Morph Contin (3-4.5 mg every 12 hours), with the lower end preferred initially. 1, 2
Step-by-Step Conversion Algorithm
Step 1: Calculate Total Daily Codeine Dose
- Each Tylenol #3 contains 30 mg codeine 1
- 8 tablets × 30 mg = 240 mg codeine per day
Step 2: Convert Codeine to Morphine Equivalents
- Using standard equianalgesic ratios, 200 mg oral codeine ≈ 30 mg oral morphine 1
- 240 mg codeine ÷ 200 mg × 30 mg = 36 mg oral morphine equivalent per day
Step 3: Convert Morphine to Hydromorphone
- The conversion ratio from oral morphine to oral hydromorphone is approximately 5:1 2, 3, 4
- 36 mg oral morphine ÷ 5 = 7.2 mg oral hydromorphone per day
Step 4: Apply Cross-Tolerance Reduction
- Reduce the calculated dose by 25-50% to account for incomplete cross-tolerance between different opioids 1, 2
- 7.2 mg × 0.50 to 0.75 = 3.6 to 5.4 mg hydromorphone daily
- However, if pain was poorly controlled on the current regimen, you may use 100% of the equianalgesic dose (7.2 mg) or even increase by 25% 1
Step 5: Divide into Appropriate Dosing Schedule
- Hydro Morph Contin is dosed every 12 hours 1
- Starting dose: 3 mg every 12 hours (total 6 mg/day) if using 50% reduction
- Alternative: 4 mg every 12 hours (total 8 mg/day) if using 25% reduction or if pain was inadequately controlled 1
Critical Safety Considerations
Provide Breakthrough Medication
- Prescribe immediate-release hydromorphone for breakthrough pain at 10-15% of the total daily dose 5
- For a 6 mg/day regimen: 0.5-1 mg IR hydromorphone every 4 hours as needed
- For an 8 mg/day regimen: 1-1.5 mg IR hydromorphone every 4 hours as needed 1
Monitor and Titrate
- No washout period is needed when converting between pure opioid agonists 5
- Reassess pain control after 48-72 hours 3
- If average pain intensity remains >4/10, increase the total daily dose by 25-50% 1, 4
- Most patients stabilize within 4-21 days of conversion 3, 4
Common Pitfalls to Avoid
Codeine-Specific Considerations
- Codeine is a prodrug requiring CYP2D6 metabolism to morphine for analgesic effect 1
- Approximately 10% of patients are poor metabolizers and may have experienced inadequate analgesia on codeine 1
- If the patient was a poor responder to codeine, consider using 100% of the calculated equianalgesic dose rather than reducing it 1
Acetaminophen Discontinuation
- The patient was also receiving 2600-4000 mg acetaminophen daily (depending on Tylenol #3 formulation) 1
- Consider whether additional non-opioid analgesia is needed after conversion 1
Renal Function Advantage
- Unlike morphine and codeine, hydromorphone has less problematic metabolite accumulation, though caution is still warranted in severe renal impairment 1
- Morphine-6-glucuronide and codeine metabolites accumulate in renal insufficiency causing neurotoxicity 1, 6