Question 1

How do I convert IV morphine to oral morphine?

Accepted Answer

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.

Question 2

What is the conversion from oral morphine to oral oxycodone?

Accepted Answer

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.

Question 3

Why do I need to reduce the dose by 25–50% when switching opioids?

Accepted Answer

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.

Question 4

How do I convert morphine to a fentanyl patch?

Accepted Answer

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.

Question 5

Why isn't methadone in this calculator?

Accepted Answer

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.

Question 6

What is the morphine equivalent of tramadol 100 mg?

Accepted Answer

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.

Question 7

Should I worry about MME limits?

Accepted Answer

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.

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

Opioid Conversion (with cross-tolerance reduction)

References

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