Calculation about dilution

Nurses Medications

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Hi everyone~I am a semester 2 student nurse, I am quite confusing with dilution of medication.

Question:You need to serve your patient 2mg morphine, you have 10mg/1ml morphine. (you need to dilute morphine with 10ml NS) How many ml morphine you need to serve?

10mg/1ml morphine dilute with 10ml NS that means after dilution I will have 10mg morphine in 11ml or 10mg morphine in 10ml???

MunoRN said:
It's actually a very legitimate question, since based on the question you would be ending up with a final volume of 11mls. This is often how the question is phrased in nursing school: "dilute with 10ml NS", which is different than "dilute with NS to produce 10mg/10ml". Leaving aside that seems to be perpetuating the myth that these medications need to be diluted at all, the correct answer to the question as written would be that you would have a concentration of 10mg/11ml, and to give 2mg you would give 2.2 ml, which if course is silly and why the more correct answer is that the instructor who wrote this question is not to bright.

What's confusing me is first he said the instructor said to dilute it in 10 mls then it was 9 so I'm not sure what the original question was. As for diluting, in peds/neo we do have to dilute so we get accurate and measurable amounts. Not so much with adults.

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Specializes in Critical Care.
Wuzzie said:
What's confusing me is first he said the instructor said to dilute it in 10 mls then it was 9 so I'm not sure what the original question was. As for diluting, in peds/neo we do have to dilute so we get accurate and measurable amounts. Not so much with adults.

And maybe the OP can clarify, but my understanding was that it was explained correctly in the lecture (add 9ml of NS to 1ml of medication to make 10mls total), but that the homework or test question said to "add 10mls of NS". This is often how instructors worded these questions when I was in school and it drove me a bit nuts, when we'd point out that adding (10mls in this example) that the resulting total volume wouldn't be 10mls, they'd often respond with "well, you know what we mean".

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MunoRN said:
And maybe the OP can clarify, but my understanding was that it was explained correctly in the lecture (add 9ml of NS to 1ml of medication to make 10mls total), but that the homework or test question said to "add 10mls of NS". This is often how instructors worded these questions when I was in school and it drove me a bit nuts, when we'd point out that adding (10mls in this example) that the resulting total volume wouldn't be 10mls, they'd often respond with "well, you know what we mean".

True dat!

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MunoRN said:
It's actually a very legitimate question, since based on the question you would be ending up with a final volume of 11mls. This is often how the question is phrased in nursing school: "dilute with 10ml NS", which is different than "dilute with NS to produce 10mg/10ml". Leaving aside that seems to be perpetuating the myth that these medications need to be diluted at all, the correct answer to the question as written would be that you would have a concentration of 10mg/11ml, and to give 2mg you would give 2.2 ml, which if course is silly and why the more correct answer is that the instructor who wrote this question is not to bright.

This answer is exactly what I need, thank you TvT

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Specializes in 15 years in ICU, 22 years in PACU.
sallyrnrrt said:
I generally don't do home work

You have on hand10mg/1ml. Morphine, you need to give( not serve) 2mg. Morphine diluted in saline flush

Each 1ml of 10 mg morphine, contains 1mg of morphine per 0.1ml...... There fore to give 2mg, you would add to the flush

0.2ml of the stock 10mg / 1 ml of morphine......

If you added 1ml of your stock solution to even 100mls. normal saline, regardless of the dilution, you would be giving 10mg morphine, instead of 2 mg.......

Geezer. This is high school math

OMG! This advice to give 2mg of morphine is mathmatically correct but not practical and nobody would do this in real life.

The point of diluting the morphine is to more accurately give 2mg. Drawing 0.2 ml of the 10mg/ml solution is asking for trouble.

Khoo Sereen said:
you have 10mg/1ml morphine. (you need to dilute morphine with 10ml NS) How many ml morphine you need to serve?

10mg/1ml morphine dilute with 10ml NS that means after dilution I will have 10mg morphine in 11ml or 10mg morphine in 10ml???

Unfortunately the question is poorly written in that you DO NOT dilute with 10ml of NS you dilute to 10ml. As previously stated, you add the 1 ml of morphine to 9 ml of NS to make a total of 10ml of solution containing 10mg of morphine. Now it is easy to draw up 2ml of solution containing 2mg of morphine.

In real life, if you don't immediately waste the remaining morphine, you would be sure to label your remaining 8ml of NS (Morphine 1mg/ml), as it contains 8mg of morphine.

That's how the smart kids do it.

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On 3/21/2018 at 2:10 PM, Mavrick said:

If you don't immediately waste the remaining morphine, you would be sure to label your remaining 8ml of NS (Morphine 1mg/ml), as it contains 8mg of morphine.

That is exactly correct, especially at ICU.

Meanwhile, Morphine is compatible to both water for injection and normal saline.

Certainly, a larger Morphine dose via IV infusion would be diluted with normal saline.

Regarding a smaller Morphine dose via IV injection, many nurses dilute 10 mg/mL Morphine with normal saline instead of water for injection.

According to Australian Injectable Drugs Handbook 7th edition, the requirement for Morphine IV injection is as follows:

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IV injection:

Dilute the dose in 4-5 mL of water for injection and inject slowly over 4 to 5 minutes for rapid onset of action.

Practice example: Dilute the 10 mg/mL ampoule with 9 mL of water for injection to make a concentration of 1 mg/mL.

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Is water for injection or normal saline the first choice for Morphine dilution before IV injection?

What is the rationale of your choice?

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why is any hospital providing Morphine 10 mg/ml vials? If you are practicing in the US, concentrated morphine should not be available on the nursing unit. Your hospital pharmacy should be dispensing products with the most appropriate size and dilution. For a Morphine 2 mg dose, the pharmacy should be providing either a 2 mg vial or a 2 mg prefilled syringe/cartridge.

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On 3/21/2018 at 2:10 PM, Mavrick said:

In real life, if you don't immediately waste the remaining morphine, you would be sure to label your remaining 8ml of NS (Morphine 1mg/ml), as it contains 8mg of morphine.

That's how the smart kids do it.

This is what the smart kids do when having to deal with more narcotic than is presently needed for the patient's dose: Waste it immediately with a witness and document having done so. This prevents opportunities (for the dumb kids who have nothing better to do) to cause trouble about "diversion."

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