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Those Nasty Opioid Conversions: How to do them.

1. Don’t memorize the tables! Memorize where you put the tables (they should be in your pocket) and how to use them!

2. There are a number of ways to do this---use the method you feel comfortable with that gives you the correct answer.

3. Don’t hesitate to use a pocket electronic calculator

Basic Procedure to convert from “old” to “new” opioid regimen:

1. Calculate the total dose of the “old” opioid in a 24 hour period.

2. Make the following equation; the dose equivalency of “old” and “new” opioid, taken from the table, page 14 APS Pain Manual, goes in the numerator!

mg “old” opioid = mg “new” opioid

current mg of “old” in 24 hr X

Where X = mg of “new” opioid in a 24 hour period.

3. Divide the 24 hour dose of the “new” opioid to obtain the desired interval dose (eg., q4h, q12h, etc.)

Some Examples:

example 1: A patient who been taking 10 mg of oxycodone q3h PO can no longer swallow; you want to start a continuous IV morphine infusion at an equianalgesic dose.

1. 10 mg oxycodone q3h = 10 x (24/3) = 80 mg oxycodone/24 hrs.

2. Table 3 (page 14) of APS Pain Manual (4^th Edition) says that 30 mg PO oxycodone = 10 mg of morphine (note: recent studies suggest that the equivalency is really 20 mg PO oxycodone = 10 mg IV morphine, but we will use the one in the table for the example)

Make the dosage ratio:

30 mg PO oxycodone = 10 mg IV morphine

80 mg PO oxycodone/24 hrs X mg IV morphine/24 hrs

X = 27 mg IV morphine/24 hrs

3. The hourly infusion rate = 27 mg/24 hrs = 1.125 mg IV morphine per hour (you can round off to 1 mg/hr)

example 2: A patient with a pathologic fracture had satisfactory relief of pain with an IV morphine infusion of 6 mg per hour. You want to send her home on an equianalgesic dose of sustained release oral morphine (MS Contin or OraMorph SR given q12h, or Kadian q day).

1. 6 mg/hr = 144 mg IV morphine/24 hrs

2. Ratio:

10 mg IV morphine = 30 mg PO morphine

144 mg IV morphine/24 hrs X mg PO morphine/24 hrs

X = 432 mg PO morphine/24 hrs – Kadian can be given once per day

3. The q12h dose = 216 mg (MS Contin or OramorphSR) PO q12h --rounding to accommodate pill size = ~ 200 mg q12h

4. Calculate the PRN dose for “breakthrough” pain: Divide the 24 hr sustained release morphine dose (400 mg) by 6 = 66 mg immediate acting morphine PO q2h PRN.

example 3: Same as example 2, but the patient’s pain was controlled by an IV infusion of hydromorphone (Dilaudid) at 1 mg/hr. Calculate the equianalgesic q12h sustained-release morphine dose.

1. 1 mg/hr = 24 mg IV hydromorphone/24 hrs

2. Ratio:

1.5 mg IV hydromorphone = 30 mg PO morphine

24 mg IV hydromorphone/24 hrs X mg PO morphine/24 hrs

X = 480 mg PO morphine/24 hrs

3. The q12h dose = 240 mg sustained-release morphine PO q12h

Adapted from:
Weissman DE, Dahl JL, Dinnorf PA.
Handbook of Cancer Pain Management, 5th Edition..
Wisconsin Cancer Pain Initiative, Madison, WI, 1996.

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