Wasting Morphine Medication Calculation Problem

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Hey guys I wanted some help with this question: The doctor prescribes 4 mg of I.M. morphine every 3 hours for your patient's pain. The drug is available in a prefilled syringe containing 10 mg of morphine/mL. How many milliliters of morphine should you waste?

I understand that you should give 0.4mL to the patient but how much do you waste? If anybody could help me understand this part of the question I would really appreciate it. Thanks guys :sneaky:

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Specializes in UM.

you would have 0.6ml left

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Specializes in Trauma, Teaching.

You didn't say how many mL are in the syringe. Not all concentrations are the same. If this is 10mg/mL, then you would subtract what you give from the total you started with. Whatever is left over is what you waste.

10 mg/mL, give 0.4, waste 0.6.

Some prefilled syringes are 4mg/mL, some are 2mg/mL. You have to read the labels very carefully.

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Thanks guys that really helped ;)

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Specializes in Trauma, Teaching.

You're welcome, and looking back a 2nd time, ah, you did say per mL. oops. :shy:

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can someone explain how you got 0.6?

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You have 10 mg morphine in 1 mL, and need to administer 4 mg.

You know that you have to administer 4 mg. How many mL will you have to administer 4 mg?

Now, you have to waste the remaining morphine. You started with 10 mg/mL. What volume of the medication did you have for the 4 mg dose that you administered? Subtract that from what you started with.

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so I'm administering 4mg/0.4mL and I have a total of 10mg/mL but I'm still not arriving at 0.6. URGHHH I FEEL DUMB!

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If i subtract 10 from .4 I get 9.6

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You don't have 10 mL. You have 10 mg in 1 mL.

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10 x 4

---- ---- = 10x =4= x=4/10 or .4ml Dose wanted Subtract dose wanted from original

1ml X. Quantity (1ml) 1ml minus .4=.6

.6 is wasted.

i tried to type this on my tablet but it didn't format the way I typed it sorry. Not sure this will help

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You have a total of 1ml. You are administering 0.4ml. 1-0.4=? It's simple math. Don't overthink it.

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