Can you check my dosage calc problem?

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Erythromycin is ordered at 750 mg in 100ml of d5w IV over 1hr and 1gm vial of erythromycin is available. The nurse is instructed to reconstitute with 20ml of sterile water. How many mL will the nurse add to d5w to administer the correct dose.

this is how I worked the problem: 750mg/1gm x 20ml/1 x 1gm/1000mg = 15000/1000=15ml is this right?

any help would be greatly appreciated!

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Specializes in NICU, ICU, PICU, Academia.

That is correct

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Yes, this is what I calculated.

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Specializes in Step-down ICU.

I got 15 by doing 750/1000*20=

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Specializes in None yet..

I haven't started nursing school yet so I'm not "thinking like a nurse" but here's how I figured it:

Goal is to administer 750 mg of the drug.

I'll prepare a solution of 1g/20mL. Convert to the same units using a factor of 1000mL/g = 1000mg/20mL = 50mL/g of drug in the solution.

There is some quantity Q of the prepared solution will deliver 750 mg of the drug.

Q * 50mg/mL = 750mg

Q = 750mg * mL/50mg

Q = 15 mL

Was anyone else slow when they started calculating dosages? Will I get faster, do you think? Right now I need to plod through step by step. I can't imagine writing out one long string of variables or jumping right to the ration.

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Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.
I haven't started nursing school yet so I'm not "thinking like a nurse" but here's how I figured it:

Goal is to administer 750 mg of the drug.

I'll prepare a solution of 1g/20mL. Convert to the same units using a factor of 1000mL/g = 1000mg/20mL = 50mL/g of drug in the solution.

There is some quantity Q of the prepared solution will deliver 750 mg of the drug.

Q * 50mg/mL = 750mg

Q = 750mg * mL/50mg

Q = 15 mL

Was anyone else slow when they started calculating dosages? Will I get faster, do you think? Right now I need to plod through step by step. I can't imagine writing out one long string of variables or jumping right to the ration.

No need to think like a nurse here...it's all just math. ;)

Well done

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Specializes in None yet..
No need to think like a nurse here...it's all just math. ;)

Well done

Whew! Thanks, Esme12!!! That's such a less terrifying way to think of it! (Seeing monsters under every bed now that the start date for nursing school is six weeks away.)

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What Esme says :). And yes, it will get quicker- you will start to "see" the necessary info much quicker after doing many calculations. For example, I see "what is 3/4 of 20?" When I read that problem. You start to do it in your head :). You'll get there- and it won't take long! :)

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Specializes in Pedi.
What Esme says :). And yes, it will get quicker- you will start to "see" the necessary info much quicker after doing many calculations. For example, I see "what is 3/4 of 20?" When I read that problem. You start to do it in your head :). You'll get there- and it won't take long! :)

Yup, that's what I saw too. 750 mg/1000 mg = 3/4. I can figure out what 3/4 of 20 is in my head.

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