NAPLEX Question of the Week: Opiate Dosing

With the ongoing opioid epidemic causing significant morbidity and mortality, this week's question will focus on potency.
NAPLEX Question of the Week: Opiate Dosing

Rank the following opiates with doses from highest to lowest dose based on currently accepted equianalgesic dosing conversions assuming no cross-tolerance:

A. Morphine 10mg IV

B. Hydromorphone 2mg IV

C. Fentanyl 12.5mcg IV

D. Oxycodone 10mg PO

Answer with rationale:

Opiate dosing is an important part of pharmacy practice. This can include initiation of opiate therapy as well as converting from one opiate to another. There are a number of excellent resources in AccessPharmacy, including the Pain Management chapter in the 11th edition of Pharmacotherapy: A Pathophysiologic Approach found here: In Table 77-11, a list of commonly available opiate analgesics with equianalgesic doses can be found. For the agents in this question, the typical equianalgesic doses are the following: Morphine 10mg IV = Hydromorphone 1.5mg IV = Oxycodone 15-30mg PO = Fentanyl 125mcg IV. Based on these equianalgesic doses using morphine as the reference, the highest dosage listed would be the hydromorphone followed by morphine then oxycodone and then finally fentanyl. Therefore the correct order would be B-A-D-C.

Keep in mind that potency does not equal effectiveness. While fentanyl is a more potent agent based on its mcg dosing, this does not mean that it is any more effective than morphine dosed in mg at equianalgesic doses. 

Good luck studying until next week. Keep grinding as it will be worth it in the long run!

Dr. B

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Go to the profile of TK
over 2 years ago

Thank you for referencing the book! sometimes we need to dive more , and this is a perfect reference!