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Discussion

Dosage calculation

Hello,

I am working on a calculation for changing from one IV opioid to another and maintaining approximate equal pain relief. I'm just having trouble figuring out if i'm setting up my equation correctly.

Question: If a patient is receiving meperidine 25 mg/hr via continuous IV drip, how much morphine IV/hr would be required for the same analgesic effect?

We have a chart that says meperidine 75 mg IV is equivalent to 10 mg IV for morphine sulfate.

So i set up my calculation as: 75 mg X 25 mg

-------- --------

10 mg X mg

75 (X) = 10 (25)

75 x = 250

x=3.33 mg/hr of morphine

This doesn't really seem right for me, but this is the most logical equation i can seem to come up with.... what do you guys think?

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    • Featured Replies

    Why don't you think it seems right?

    75mg/hr of meperidine = 10mg/hr of Morphine

    So if I need 25mg/hr of meperidine, I would need less mg of morphine than 10mg/hr.

    It makes total sense to me.

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    • Author

    I'm not sure why i thought it didn't make sense, maybe because we haven't been taught how to actually convert between opioid medications. But yeah, I just didn't understand how the number could be lower than 10. but if that is the answer that you guys are coming up with then it should be right? i tried working on it last night but gave up and then i looked at it again this morning and this is what I got. Thank you.

  • Quote
    I'm not sure why i thought it didn't make sense, maybe because we haven't been taught how to actually convert between opioid medications. But yeah, I just didn't understand how the number could be lower than 10. but if that is the answer that you guys are coming up with then it should be right? i tried working on it last night but gave up and then i looked at it again this morning and this is what I got. Thank you.

    Think of it this way: If the number is higher than 10, you will be giving more than 75mg/hr meperidine. Is the patient ordered to get more than 75?

    but yeah, 3.33 sounds right.

  • Quote
    • Author
    Think of it this way: If the number is higher than 10, you will be giving more than 75mg/hr meperidine. Is the patient ordered to get more than 75?

    but yeah, 3.33 sounds right.

    Alright yeah, that makes sense since its only 25 mg/hr of meperidine

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    Think of it like this... 75 is equal to 10. You are delivering a third of 75 (25), so your equivalent should be a third of 10 (3.33). If you were delivering double the 75 (150), then you could double the 10 to get the equivalent (20).

  • Quote
    • Author
    Think of it like this... 75 is equal to 10. You are delivering a third of 75 (25), so your equivalent should be a third of 10 (3.33). If you were delivering double the 75 (150), then you could double the 10 to get the equivalent (20).

    hmm didn't think of it that way..thanks!!!

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