Equianalgesic Doses of Opioid Analgesics*,†,‡

* Equivalences are based on single-dose studies influenced by clinical experience. Cross-tolerance between medications is incomplete, so when one medication is substituted for another, the equianalgesic dose should be reduced by 50%; methadone should be reduced by 75–90%. Some experts have suggested that morphine:methadone equivalence is nonlinear and that it changes when morphine dosage is higher, as in the following morphine-to-methadone conversion ratios:* Equivalences are based on single-dose studies influenced by clinical experience. Cross-tolerance between medications is incomplete, so when one medication is substituted for another, the equianalgesic dose should be reduced by 50%; methadone should be reduced by 75–90%. Some experts have suggested that morphine:methadone equivalence is nonlinear and that it changes when morphine dosage is higher, as in the following morphine-to-methadone conversion ratios:

• < 30 OMME/day: 2:1

• 31–99 OMME/day: 4:1

• 100–299 OMME/day: 8:1

• 300–499 OMME/day: 12:1

• 500–999 OMME/day: 15:1

• ≥ 1000 OMME/day: 20:1

Methadone dosage should still be reduced by 75–90% even when this more conservative equivalence calculation is used. Methadone dosage should still be reduced by 75–90% even when this more conservative equivalence calculation is used.

† See also Kreutzwiser D, Tawfic QA and Pain Guidelines (based on Quill TE: Primer of Palliative Care, ed. 7. Chicago, Academy of Hospice and Palliative Medicine, 2019).

‡ Additional recommendations for even more conservative dosing regimens are available in the following resources:

Chou R, Cruciani RA, Fiellin DA, et al. Methadone safety: a clinical practice guideline from the American Pain Society and College on Problems of Drug Dependence, in collaboration with the Heart Rhythm Society. . Methadone safety: a clinical practice guideline from the American Pain Society and College on Problems of Drug Dependence, in collaboration with the Heart Rhythm Society.J Pain. 2014;15(4):321-337. doi:10.1016/j.jpain.2014.01.494

McPherson ML, Walker KA, Davis MP, et al. Safe and Appropriate Use of Methadone in Hospice and Palliative Care: Expert Consensus White Paper. . Safe and Appropriate Use of Methadone in Hospice and Palliative Care: Expert Consensus White Paper.J Pain Symptom Manage. 2019;57(3):635-645.e4. doi:10.1016/j.jpainsymman.2018.12.001

§ Parenteral oxycodone is available in Europe but not in the United States.§ Parenteral oxycodone is available in Europe but not in the United States.

OMME = oral morphine milligram equivalents.