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Opioids - Equianalgesic Dosages

Before using the data below, please review these important points:


bullet 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. 

bullet 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. 

bullet Conversion ratios in many equianalgesic dosing tables do not apply to repeated doses of opioids.

bullet Review the concept of incomplete cross-tolerance:

D. McAuley:   "Incomplete cross-tolerance relates to tolerance to a currently administered opiate that does not extend completely to other opioids. This will tend to lower the required dose of the second opioid. This incomplete cross-tolerance exists between all of the opioids and the estimated difference between any two opiates could vary widely. This points out the inherent dangers of using an equianalgesic table and the importance of viewing the tabulated data as approximations. Many experts recommend - depending on age and prior side effects - reducing the dose of the new opiate by 33 to 50 percent to account for this incomplete cross-tolerance. (Example: a patient is receiving 200mg of oral morphine daily (chronic dosing), however, because of side effects a switch is made to oral hydromorphone 25 - 35mg daily - (this represents a 33 to 50 percent reduction in dose compared to the calculated 50mg conversion dose produced via the equianalgesic calculator). This new regimen can then be re-titrated to patient response. In all cases, repeated comprehensive assessments of pain are necessary in order to successfully control the pain while minimizing side-effects."


bullet 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.

bullet The use of high but ineffective doses of a previous opioid may result in overestimation of the converted opioid. 

bullet 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. 

bullet 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:
0-99 mg: 4:1  
100-299 mg: 8:1
300-499 mg: 12:1
500-999 mg:  15:1
>1000 mg:  20:1
Fentanyl Patch Conversions - Package Insert Recommendations
RECOMMENDED INITIAL DURAGESIC® DOSE BASED UPON DAILY ORAL MORPHINE DOSE4
Oral 24-hour
Morphine
(mg/day)
DURAGESIC®
Dose
(mcg/h)
NOTE: In clinical trials, these ranges of daily oral morphine doses were used as a basis for conversion to DURAGESIC®.
This table should not be used to convert from DURAGESIC® to other therapies because this conversion to DURAGESIC® is conservative. Use of this table for conversion to other analgesic therapies can overestimate the dose of the new agent. 
60–134 25
135–224 50
225–314 75
315–404 100
405–494 125
495–584 150
585–674 175
675–764 200
765–854 225
855–944 250
945–1034 275
1035–1124 300
Discontinuation of DURAGESIC®:
To convert patients to another opioid, remove DURAGESIC® and titrate the dose of the new analgesic based upon the patient's report of pain until adequate analgesia has been attained. Upon system removal, 17 hours or more are required for a 50% decrease in serum fentanyl concentrations. Opioid withdrawal symptoms (such as nausea, vomiting, diarrhea, anxiety, and shivering) are possible in some patients after conversion or dose adjustment. For patients requiring discontinuation of opioids, a gradual downward titration is recommended since it is not known at what dose level the opioid may be discontinued without producing the signs and symptoms of abrupt withdrawal.
References
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: http://www.duragesic.com/prescribing-information.html
     Accessed: October 2010.

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.
Drug  Duration     Half-life    Route       Equianalgesic
 Dosage
Codeine 4–6 h 3 h IM 120 mg
      PO 200 mg
Fentanyl 1–2 h 1.5–6 h IM 0.1 mg
Hydrocodone 4–8 h 3.3–4.5 h PO 30 mg
Hydromorphone 4–5 h 2–3 h IM 1.3–1.5 mg
      PO 7.5 mg
Levorphanol 6–8 h 12–16 h IM 2 mg
      PO 4 mg
Meperidine 2–4 h 3–4 h IM 75 mg
      PO 300 mg
Methadone 4–6 h 15–30 h IM 10 mg
      PO 10–20 mg
Morphine 3–7 h 1.5–2 h IM 10 mg
      PO 30–60 mg
Oxycodone 4–6 h NA PO 15-30 mg (20 mg)
Oxymorphone 3–6 h NA IM 1 mg
      PR 10 mg
Propoxyphene 4–6 h 6–12 h PO 130-200 mg *
(Inconclusive data)
*Propoxyphene HCL: 130mg;  Napsylate: 200mg. Not recommended for chronic pain.

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