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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)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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