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Example 2

Levy’s Rule Example 2

Mr. Tom Hack, a terminally ill, colon cancer patient

Mr. Tom Hack, a terminally ill colon cancer patient has pain that is well controlled on Morphine Sustained Action, 90mg every 8 hours. Mr. Hack is now unable to swallow and so the Morphine needs to be converted into a transdermal fentanyl patch. Calculate the hourly dose of the fentanyl patch.

To calculate the hourly dose of the fentanyl patch:
Step 1 Total dose of sustained release morphine taken over 24 hours

3 x 90 mg = 270 mg
Step 2 Half of total dose of sustained release morphine taken over 24 hours

(The Levy rule states that the hourly fentanyl patch strength in micrograms is half of the total daily dose of sustained release morphine in milligrams.)

270 mg / 2 = 135 mg
Step 3 Therefore the rough fentanyl equivalent for 270 mg of morphine =

135 micrograms of fentanyl / hour
Step 4 The fentanyl patch comes in multiples of 25 micrograms. So round up the calculated 135 micrograms dosage of fentanyl to 125 micrograms or a 150 microgram patch depending on whether patient’s pain is under good control or not.
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