Opioid Conversion (with cross-tolerance reduction)
Morphine-equivalent conversion across morphine, oxycodone, hydromorphone, hydrocodone, and fentanyl patch with explicit 25–50% cross-tolerance reduction.
- Rotating an opioid for inadequate analgesia, side-effects, or formulary
- Converting a patient from PO to IV during a hospitalization (or vice versa at discharge)
- Estimating a patch strength when transitioning to long-acting therapy
- Sanity-checking a basal/bolus PCA order against a home regimen
- Always apply a cross-tolerance reduction. This is the single most-skipped step and the source of most rotation overdoses. Default to 25–50% reduction; pick 50% in opioid-naïve, elderly, sleep apnea, renal failure, or any clinical concern about respiratory drive.
- MME is a tool, not a target. The CDC 2022 guideline reframed MME as "consider individualized factors" rather than a hard ceiling — but high MMEs (>50, >90/day) remain a flag for closer monitoring and a non-opioid plan.
- Fentanyl patches are nonlinear. Conversions are conservative and onset/offset are slow (18–24 hr). Don't titrate a patch every day; wait at least 72 hours before adjusting.
- Methadone is not in this tool. Its conversion is dose-dependent, its half-life is variable, and its QT and respiratory risks are unique. Rotate to or from methadone with palliative care or pain specialist supervision.
- Renal failure changes the picture. Morphine accumulates M3G/M6G; codeine and tramadol require CYP2D6 conversion. Hydromorphone and fentanyl are generally safer in advanced CKD.
- Breakthrough dosing. A common pattern is 10–15% of the 24-hour total as the breakthrough dose (PRN q1–2h PO or q15–30min IV).
Opioid rotation is one of the highest-stakes routine prescribing tasks: get it right and pain improves, get it wrong and the patient stops breathing. The mistakes are usually not in the table — they are in skipping the cross-tolerance reduction or applying it to a methadone rotation that should not have been attempted unsupervised.
Sum of all doses in 24 hr
Input MME / day
60MME
After reduction
40MME
| Drug | Raw equivalent | After reduction |
|---|---|---|
| Morphine PO | 60mg/day | 40mg/day |
| Morphine IV/SC | 20mg/day | 13mg/day |
| Oxycodone PO | 40mg/day | 27mg/day |
| Hydromorphone PO | 15mg/day | 10mg/day |
| Hydromorphone IV/SC | 3mg/day | 2mg/day |
| Hydrocodone PO | 60mg/day | 40mg/day |
| Codeine PO | 400mg/day | 270mg/day |
| Tramadol PO | 600mg/day | 400mg/day |
| Fentanyl transdermal | 25mcg/hr | 16.8mcg/hr |
| Tapentadol PO | 150mg/day | 100mg/day |
Fentanyl patch — nearest strength: 12 mcg/hr
Fentanyl patch conversions are nonlinear and conservative. Available strengths: 12, 25, 37.5, 50, 75, 100 mcg/hr. When initiating a patch, plan for an 18–24 hour onset and a 12–24 hour offset after removal.
Methadone is not a linear conversion
Methadone is intentionally omitted from this tool. Its conversion ratio depends on the starting MME (the higher the dose, the more potent methadone becomes — sometimes 1:20 at higher MMEs), and it has unique QT and respiratory risks. Methadone rotation is a specialist task — pain or palliative care should drive it.
Always reduce 25–50% for incomplete cross-tolerance
Tolerance is opioid-specific only in part. When rotating between agents, the new drug typically appears more potent than the table predicts. Standard practice is to reduce the calculated equivalent dose by 25–50% (33% is a reasonable default), then titrate to effect. In opioid-naïve patients or those with respiratory comorbidities, reduce by 50%.
Frequently asked
How do I convert IV morphine to oral morphine?
The standard ratio is IV : PO = 1 : 3. So 10 mg IV morphine over 24 hours equals approximately 30 mg PO morphine over 24 hours. After conversion, apply a 25–50% cross-tolerance reduction and then titrate to effect.
What is the conversion from oral morphine to oral oxycodone?
Oral oxycodone is roughly 1.5× as potent as oral morphine. Morphine 30 mg PO ≈ oxycodone 20 mg PO. Some references cite a 1:1 ratio for "oxycodone is similar to morphine," which is dangerously imprecise — especially in opioid-naïve patients.
Why do I need to reduce the dose by 25–50% when switching opioids?
Tolerance is incomplete across opioids — meaning a patient tolerant to one agent is not fully tolerant to another, even at the mathematically equivalent MME. The new drug therefore behaves as if more potent than the conversion table predicts. Standard practice is a 25–50% reduction at rotation, with closer titration to effect after.
How do I convert morphine to a fentanyl patch?
A common conservative rule: oral morphine (mg/24 hr) divided by ~2.4 ≈ fentanyl patch (mcg/hr). So morphine 60 mg/day ≈ 25 mcg/hr patch. Available patch strengths are 12, 25, 37.5, 50, 75, and 100 mcg/hr. Round down rather than up, and remember the 18–24 hour onset.
Why isn't methadone in this calculator?
Methadone equivalence is dose-dependent, not linear. At low MMEs (under ~100/day) it is roughly 1:4 vs morphine; at high MMEs (over ~1000/day) it can be 1:20 or more. Methadone also has unique QT, drug-interaction, and respiratory risks, and a long variable half-life. Rotation should be done by pain or palliative care specialists, not from a table.
What is the morphine equivalent of tramadol 100 mg?
Approximately 10 MME — tramadol is roughly 0.1× the potency of oral morphine on a mg basis. The conversion is contested because tramadol's analgesic mechanism is partly non-opioid (SNRI) and CYP2D6-dependent, so individual response varies dramatically.
Should I worry about MME limits?
The 2022 CDC guideline removed the previous hard 90 MME/day threshold but recommends careful evaluation for patients above 50 MME/day and reassessment of risks and benefits above 90. The numbers are screening triggers, not absolute limits — chronic cancer pain, palliative care, and titration after rotation can all legitimately exceed them.