Morphine Equivalents

CRNA Study Suite · Opioid Conversion & PCA
Convert
Equianalgesic Reference
Drug / RouteDose= MME (mg)
Morphine IV10 mg30
Morphine PO30 mg30
Fentanyl IV100 mcg30
Hydromorphone IV1.5 mg30
Hydromorphone PO7.5 mg30
Oxycodone PO20 mg30
Hydrocodone PO30 mg30
Codeine PO200 mg30
Tramadol PO300 mg30
CDC Opioid Prescribing Guideline conversion factors (widely used clinical reference)
Conversion Result
Input Dose
--
mg
= Oral Morphine (MME)
--
mg
= Morphine IV equivalent
--
mg
= Hydromorphone IV
--
mg
= Fentanyl IV
--
mcg
= Oxycodone PO
--
mg
Cross-tolerance reduction: When rotating opioids, reduce the calculated equivalent by 25-50% to account for incomplete cross-tolerance. Always titrate to effect.
Calculation Breakdown
Step 1 — Convert to MME (oral morphine equivalent)
--
Step 2 — Derive other formulations
--
PCA Starting Doses (Nagelhout Ch 56, p. 1302)
DrugBolusLockout
Morphine (1 mg/mL)0.5-2.5 mg5-10 min
Fentanyl (10 mcg/mL)10-20 mcg4-10 min
Hydromorphone (0.2 mg/mL)0.05-0.25 mg5-10 min
Methadone (1 mg/mL)0.5-2.5 mg8-20 min
⚠ Meperidine NOT recommended for PCA — normeperidine metabolite is neurotoxic (tremors, seizures, not naloxone-reversible).
(Bordi, 2023, p. 1302)
References

Bordi, S. K. (2023). Acute pain: Physiology and management. In S. Elisha, J. S. Heiner, & J. J. Nagelhout (Eds.), Nurse anesthesia (7th ed., pp. 1293-1309). Elsevier.

How this works

How MME conversion works

Morphine milligram equivalent (MME) conversion translates different opioids into a common oral morphine reference so total daily opioid exposure can be compared across agents. Using morphine as the reference (factor of 1), oxycodone converts at 1.5, hydromorphone at 5, hydrocodone at roughly 1, and transdermal fentanyl at 2.4 per mcg per hour of patch strength (Hurley et al., 2025, pp. 2530-2532).

Why you reduce the calculated dose

These factors are rough population level estimates, not precise individual predictions. When rotating from one opioid to another, cross tolerance is incomplete, so the new opioid can be more potent in that patient than the equianalgesic dose predicts. Reduce the calculated dose to about 50 to 75% and then titrate, to avoid oversedation and respiratory depression (Hurley et al., 2025, pp. 2530-2532).

References

Hurley, R. W., Elkassabany, N. M., & Wu, C. L. (2025). Acute postoperative pain. In Miller's anesthesia (10th ed., pp. 2512-2537). Elsevier.