Wasting Morphine Medication Calculation Problem

0 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 


Jan 20, '13 by JBudd, MSN GuideYou 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. 

Jan 20, '13 by JBudd, MSN GuideYou're welcome, and looking back a 2nd time, ah, you did say per mL. oops.


Nov 1 by chareYou 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. 
Nov 1 by bklynfinestso 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!



Nov 2 by RNKPCE10 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 helpLast edit by RNKPCE on Nov 2 : Reason: Trying to improve format 
Nov 2 by WuzzieYou have a total of 1ml. You are administering 0.4ml. 10.4=? It's simple math. Don't overthink it.