When giving methylnatrexone subcutaneously, if the dose is 12 mg and the concentration available is 8 mg/0.4 mL, how many mL should the nurse administer?

To determine the correct volume of methylnaltrexone to administer, it's important to calculate how much volume corresponds to the prescribed dose of 12 mg given the concentration available.

The available concentration is 8 mg in 0.4 mL. To find out how much volume is needed to achieve a dose of 12 mg, we can set up a proportion based on the concentration:

1. First, calculate how much methylnaltrexone is in 1 mL using the provided concentration:

   • If 0.4 mL contains 8 mg, then:
   • To find out how much is in 1 mL:
     • ( \frac{8 , \text{mg}}{0.4 , \text{mL}} = 20 , \text{mg/mL} )

2. Next, using the concentration of 20 mg/mL, determine the volume needed to get a dose of 12 mg:

   • Use the formula:
     • ( \text{Volume (mL)} = \frac{\text{Desired Dose (mg)}}{\text{Concentration (mg/mL)}} )

   • Substituting the values: