Dosing Calculation ... help!

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I need help with a dosage calculation. The problem is as follows:

The order is for demerol 35mg with versed 0.6mg IM prior to a colonoscopy. Available to the nurse is demerol 50mg/ml and versed 1mg/ml. The nurse would administer a total of how many ml's?

I am totally stumped on this one. Can someone please tell me how to set up this problem? Thanks!

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I think you figure them out totally separate, then you are combining them in the one IM injection.

So I get 0.7 mL from the demerol portion, 0.6 mL from the Versed portion, combined for a total IM injection of 1.3 mL.

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Okay, you must be right because the answer is 1.3ml I just couldn't figure out how to get there! Thanks!

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Specializes in PICU, Sedation/Radiology, PACU.

For most dosage calculations not involving drip rates, you use the following formua:

Desired dose/Available dose x volume

The volume is whatever the dose is contained in. For example, if you have 25 mg in one pill, the volume is one. If you have 25mg in 5mls the volume is 5.

For this question, you have to calculate both dosages seperately and add them together.

So for the demerol:

Desired dose 35 mg / Available dose 50 mg x volume 1mL = 0.7ml

For the versed:

Desired dose 0.6 mg / Available dose 1 mg x volume 1mL = 0.6 mL

0.7 + 0.6 = 1.3 mL total.

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Sorry for the silly question but I was just wondering...when nurses have a lot of calculations to figure out do they usually do them in their head on the fly or do they have a calculator with them all the time?

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I remembered the formula as devil over hell times the lost souls which = dose over or divided by what is on hand times the mg, ml,pills

7/3.5x2 =4 Hope that may help

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Specializes in PICU, Sedation/Radiology, PACU.
Sorry for the silly question but I was just wondering...when nurses have a lot of calculations to figure out do they usually do them in their head on the fly or do they have a calculator with them all the time?

I keep a calculator in my pocket and use it frequently during work. I use it for dosage calculations and tabulating I&Os. Even if a medication comes from the pharmacy with a dose on the label, I always double check myself. We also have to dilute medications or draw from a multi-dose vial, so I do a lot of calculations.

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Specializes in being a Credible Source.
Sorry for the silly question but I was just wondering...when nurses have a lot of calculations to figure out do they usually do them in their head on the fly or do they have a calculator with them all the time?
I can only speak for this nurse but I always keep a calculator in my pocket. Nothing worse than being hella busy and not being able to find one.

I *can* do many of the simpler calcs in my head but I *never* do...

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Specializes in Obstetrics.

I use the desired/on hand x vehicle equation. In this equation you do it separately and then add the two results together so: Demerol desired is 35mg/50mg x ml= 0.7

Versed desired is 0.6mg/1mg x ml= 0.6ml. 0.7ml of Demerol and 0.6ml of Versed= 1.3ml total.

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Specializes in Medical Surgical/Addiction/Mental Health.

"I remembered the formula as devil over hell times the lost souls "

Love it!!!

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Sorry for the stupid question but I don't understand. If you have

35mgx1mg=0.7 is that not the answer? Why do you add the 0.6ml?

50mg

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Specializes in PICU, Sedation/Radiology, PACU.
Sorry for the stupid question but I don't understand. If you have

35mgx1mg=0.7 is that not the answer? Why do you add the 0.6ml?

50mg

Go back and read the original question. The order says to give 35mg of demerol and 0.6mg of versed. The question asks for the total mLs that you will administer. 0.7mL of demerol plus the 0.6 mL of versed = 1.3 mLs.

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