Wasting Morphine Medication Calculation Problem

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, '13You 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. 



Nov 1, '16You 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, '16so 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, '1610 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, '16 : Reason: Trying to improve format 
Nov 2, '16You have a total of 1ml. You are administering 0.4ml. 10.4=? It's simple math. Don't overthink it.

Dec 13, '16if there are 10mg in 1 mL each 0.1 mL has 1 mg morphine which equals 0.4mL given and 0.6mL wasted.