Example 1

Levy’s Rule Example 1

Mr. John Smith, a terminally ill, lung cancer patient

Mr. John Smith, a terminally ill lung cancer patient has pain that is well controlled on Morphine Sustained Action, 90mg every 12 hours. Mr. Smith is now unable to swallow and so the morphine needs to be converted into a transdermal fentanyl patch.

To calculate the hourly dose of the fentanyl patch:

Step 1 Total dose of sustained release morphine taken over 24 hours

2 x 90 mg = 180 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.)

180 mg / 2 = 90 mg

Step 3 Therefore the rough fentanyl equivalent for 180 mg of morphine =

90 micrograms of fentanyl / hour

Step 4 The fentanyl patch comes in multiples of 25 micrograms. So round up the calculated 90 micrograms dosage of fentanyl to 100 micrograms or a 75 microgram patch depending on whether patient’s pain is under good control or not.

 

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