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Fast Fact and Concept #36: Calculating Opioid Dose Conversions

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Title: Fast Fact and Concept #36: Calculating Opioid Dose Conversions

Author(s): Robert Arnold; David E. Weissman

The need to change from one opioid to another, or from one route to another, is common. The published conversion tables provide a rough guide for making calculations . However, clinical judgement must always be used to arrive at a reasonable dose conversion. The following examples assume a change in drug or route at a time of stable pain control using equianalgesic doses. See Fast Fact #20: Opioid Dose Escalation for information about dose escalation guidelines.

Opioid Equianalgesic Values for use with the following examples**

Morphine 10 mg parenteral = Morphine 30 mg oral = Hydromorphone 1.5 mg parenteral = Hydromorphone 7.5 mg oral.

Change route, keeping drug the same (e.g. oral to IV morphine)
Example: Change 90 mg q12 MS Contin to MS by IV continuous infusion

Calculate the 24 hour current dose: 90mg q 12 = 180 mg MS/24 hours

Look up equianalgesic ratio: 30 mg po MS = 10 mg IV MS

Calculate new dose using ratios: 180/30 x 10 = 60 mg IV MS/24 hours or 2.5 mg/hour infusion

Change drug, keep the same route: (e.g. po morphine to po hydromorphone)

There is incomplete cross-tolerance between all different opioids, but the exact amount will differ, thus, equianalgesic tables are only approximations. Depending on age and prior side effects, most experts recommend starting a new opioid at 50% of the calculated equianalgesic dose.

Example: Change 90 mg q 12 MS Contin to oral hydromorphone.

1. Calculate the 24 hour current dose: 90 Q12 x 2 = 180 mg po MS/24 hrs
2. Look up equianalgesic ratio: 30 mg po morphine = 7.5 mg po hydromorphone
3. Calculate new dose using ratios: 180/30 X 7.5 = 45 mg oral hydromorphone/24 hours.
4. Reduce dose 50% for cross-tolerance: 45 x.5 = 22 mg/24 hours = 4 mg q4h

Changing drug and route (e.g. oral morphine to IV hydromorphone)

Example: Change from 90 mg q12 MS Contin to IV hydromorphone as a continuous infusion.

1. Calculate the 24 hour current dose: 90 Q12 x 2 = 180 mg po MS/24 hrs
2. Look up equianalgesic ratio of po to IV morphine: 30 mg po MS = 10 mg IV MS
3. Calculate new dose using ratios: 180/30 x 10 = 60 mg IV MS/24 hours
4. Look up equianal. ratio of IV morphine to IV hydromorphone: 10 mg MS = 1.5 mg hydromorphone
5. Calculate new dose using ratios: 60/10 x 1.5 = 9 mg IV hydromorphone/24 hours
6. Reduce dose 50% for cross-tolerance: 9 x.5 = 4.5 mg/24 hours = 0.2 mg IV continuous infusion

** See AHCPR Guidelines for full Equianalgesic Table; See Fast Fact #2 for information on dose conversions using Transdermal Fentanyl.

References

Jacox A, Carr DB, Payne R, et al. Management of Cancer Pain. Clinical Practice Guideline No. 9. AHCPR Publication No. 94-0592. Rockville, MD. Agency for Health Care Policy and Research, U.S. Department of Health and Human Services, Public Health Service, 1994. (page 54)

Gordon DB, Stevenson KK, Griffie, J, et al. Opioid equianalgesic calculations. J Pall Med 1999;2:209-218

Copyright Notice: Users are free to download and distribute Fast Facts for educational purposes only. Citation for referencing: Arnold, R and Weissman DE. Fast Facts and Concepts #36: CALCULATING OPIOID DOSE CONVERSIONS; March, 2001. End-of-Life Physician Education Resource

Contact:
David E. Weissman, MD, FACP
Editor, Journal of Palliative Medicine
Palliative Care Program Director
Medical College of Wisconsin
(P) 414-805-4607
(F) 414-805-4608

Disclaimer: Fast Facts provide educational information, this information is not medical advice. Health care providers should exercise their own independent clinical judgment. Some Fast Fact information cites the use of a product in dosage, for an indication, or in a manner other than that recommended in the product labeling. Accordingly, the official prescribing information should be consulted before any such product is used.

Creation Date: 3/2001

Format: Handouts

Purpose: Instructional Aid, Self-Study Guide, Teaching

Audience(s)
Training: Fellows, 3rd/4th Year Medical Students, PGY1 (Interns), PGY2-6, Physicians in Practice
Specialty: Anesthesiology, Emergency Medicine, Family Medicine, General Internal Medicine, Geriatrics, Hematology/Oncology, Neurology, OB/GYN, Ophthalmology, Pulmonary/Critical Care, Pediatrics, Psychiatry, Surgery
Non-Physician: Nurses

ACGME Competencies: Medical Knowledge

Keyword(s): Addiction, Chronic non-malignant pain, Controlled substance regulations, Pain, Pain assessment, Pain treatment


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