Question

You are asked to prepare a 250 mcg dose. The medication is labeled 0.3mg/ mL . How many mL will you need for the prescribed dose? Round your final answer to 3 decimal places if necessary.

Answer 1

We have to prepare a 250 mcg (micrograms) dose.

The medication is labeled 0.3 mg/mL.

We have to calculate how many mL we need for the prescribed dose.

We first express 0.3 mg as mcg. One miligram is 1/1,000 of a gram while one microgram 1/1,000,000 of a gram.

We can use this relations to find the ratio:

`\frac{1\text{ g}}{1000\text{ mg}}*\frac{1000000\text{ mcg}}{1\text{ g}}=\frac{1000\text{ mcg}}{1\text{ mg}}`

Then, we have the unit ratio: 1000 mcg are equivalent to 1 mg.

We then can convert 0.3 mg into mcg as:

`0.3\text{ mg}*\frac{1000\text{ mcg}}{1\text{ mg}}=300\text{ mcg}`

We can now apply the rule of three to find how many mL we need.

If 1 mL contains 300 mcg, then x mL will contain 250 mcg:

`\begin{gathered} (x)/(250)=(1)/(300) \\ x=(250)/(300) \\ x\approx0.833\text{ mL} \end{gathered}`

Answer: we need 0.833 mL.