OxyContin ER 15 mg every 4 hours delivers substantially more oxycodone per day and is therefore the stronger regimen
Dosing Frequency Error
OxyContin ER 12-hour formulation should never be dosed every 4 hours—this represents a critical prescribing error that triples the intended daily dose. 1, 2
- OxyContin ER is designed for administration every 12 hours, not every 4 hours 2, 3
- Dosing OxyContin ER every 4 hours would result in 6 doses per day (90 mg total daily dose) instead of the intended 2 doses per day (30 mg total daily dose) 2
- Extended-release formulations have peak plasma concentrations delayed to 2-6 hours and are specifically engineered for 12-hour duration of action 4, 3
Total Daily Dose Comparison
If OxyContin ER 15 mg is incorrectly dosed every 4 hours (as stated):
- Total daily oxycodone: 90 mg (15 mg × 6 doses)
- MME equivalent: 135 MME/day (using 1.5 conversion factor) 1
If oxycodone HCl IR 10 mg is correctly dosed every 4 hours:
- Total daily oxycodone: 60 mg (10 mg × 6 doses)
- MME equivalent: 90 MME/day (using 1.5 conversion factor) 1
The OxyContin ER regimen as written delivers 50% more total daily opioid than the immediate-release oxycodone regimen. 1
Relative Potency Considerations
- Oxycodone has an equianalgesic conversion factor of 1.5 relative to morphine (meaning oxycodone is 1.5 times stronger than morphine milligram-per-milligram) 1
- Both formulations contain the same active ingredient (oxycodone), so the only difference is total daily dose and release kinetics 2, 5
- Immediate-release oxycodone reaches peak plasma concentrations within 1 hour with 3-4 hour duration 2
- Extended-release oxycodone has 60-87% oral bioavailability and reaches peak concentrations in 2-4 hours with 12-hour duration 2, 3
Critical Safety Concerns
Dosing OxyContin ER every 4 hours places the patient at 135 MME/day, which exceeds the CDC threshold of 90 MME/day associated with significantly increased overdose risk. 1
- The CDC guideline emphasizes careful reassessment before increasing dosages to ≥50 MME/day and progressive increases in risk as dosage increases 1
- Dosages ≥90 MME/day have limited evidence of benefit and substantially elevated mortality risk 1
- Breaking, crushing, or chewing OxyContin ER tablets (or taking them more frequently than intended) can result in rapid release and absorption of a potentially fatal dose 2
Correct Prescribing Practice
The appropriate comparison should be:
- Oxycodone IR 10 mg every 4 hours (60 mg/day = 90 MME/day)
- OxyContin ER 15 mg every 12 hours (30 mg/day = 45 MME/day)
Under correct dosing, the immediate-release regimen would be twice as strong as the extended-release regimen. 1, 2
Common Pitfall
- Never increase dosing frequency of extended-release formulations—instead, increase the dose amount if pain control is inadequate 1, 6
- Modified-release formulations are designed for 12-hour intervals; more frequent dosing defeats the purpose of the extended-release mechanism and creates dangerous overdose risk 1, 4
- For breakthrough pain on a 12-hourly ER regimen, provide immediate-release oxycodone as rescue medication at 10-20% of the total daily dose, available every 1-2 hours as needed 1, 6