Opioids - Equianalgesic Dosages
Published equianalgesic ratios are considered crude estimates at best and therefore it is imperative that careful consideration is given to individualizing the dose of the selected opioid. Dosage titration of the new opioid should be completed slowly and with frequent monitoring.
Factors that must be addressed during the conversion process include: Age of the patient or presence of coexisting conditions. Use additional caution with elderly patients (65 years and older), and in patients with liver, renal, or pulmonary disease.
Conversion ratios in many equianalgesic dosing tables do not apply to repeated doses of opioids.
Review the concept of incomplete cross-tolerance:
The amount of residual drug in the patient's system must be accounted for. Example: fentanyl will continue to be released from the skin 12 to 36 hours after removal of the patch. Residual effects from discontinued long-acting formulations should also be assessed before converting a patient to a new opioid.
The use of high but ineffective doses of a previous opioid may result in overestimation of the converted opioid.
Ideally, methadone conversions (especially patients who were previously receiving high doses of an opioid) should only be attempted in cooperation with a pain specialist or a specialist in palliative medicine.
Meperidine should be used for acute dosing only and not used for chronic pain management (meperidine has a short half-life and a toxic metabolite: normeperidine). Its use should also be avoided in patients with renal insufficiency, CHF, hepatic insufficiency, and the elderly because of the potential for toxicity due to accumulation of the metabolite normeperidine. Seizures, confusion, tremors, or mood alterations may be seen. In patients with normal renal function, total daily doses should not exceed 600mg/24hrs.
|Equianalgesic dosage table|
|Buprenorphine (IM/IV): 0.4
Butorphanol (IM/IV): 2.0
Codeine (IM/IV): 120
Codeine (PO): 200
Fentanyl (IM/IV): 0.1
Fentanyl (Transdermal): 0.2
Hydrocodone (PO): 30
Hydromorphone (IV/IM/SC): 1.5
Hydromorphone (PO): 7.5
Levorphanol (acute PO): 4.0
Levorphanol (chronic PO): 1.0
Meperidine (IV/IM/SC): 75
Meperidine (PO): 300
Methadone (acute IV): 5.0
Methadone (acute PO): 10
|Morphine (IV/IM/SC): 10
Morphine (acute PO): 60
Morphine (chronic PO): 30
Nalbuphine (IV/IM/SC): 10
Oxycodone (PO): 20
Oxymorphone (IV/IM/SC): 1.0
Oxymorphone (PO): 10
Tapentadol (PO): 75-100
Methadone Chronic dosing:
|Fentanyl Patch Conversions - Package Insert Recommendations|
|1] American Pain Society (APS). Principles of Analgesic Use in the Treatment of Acute Pain and Cancer Pain, 6th edition. 2008. Glenview, IL 60025.
2] Ayonrinde OT, Bridge DT. The rediscovery of methadone for cancer pain management. Med J Aust 2000; 173(10): 536-540.
3] Breitbart W, Chandler S, Eagel B, et al. An alternative algorithm for dosing transdermal fentanyl for cancer-related pain. Oncology. 2000;14:695-705.
4] Duragesic® Package Insert:
5] Donner B, et al. Direct conversion from oral morphine to transdermal fentanyl. Pain. 1996; 64:527-534.
6] Fisch MJ, Cleeland CS: Managing cancer pain. In: Skeel RT, ed.: Handbook of Cancer Chemotherapy. 6th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2003, pp 663.
7] Methadone PI (package insert). Dolophine hydrochloride, 5 mg, 10mg tablets. Oct .2006.
8] Ripamonti C, Groff L, Brunelli C, Polastri D, Stavrakis A, De Conno F. Switching from morphine to oral methadone in treating cancer pain: what is the equianalgesic dose ratio? J Clin Oncol. 1998;16(10):3216-3221.