Question

1. the physician orders cefazolin 500 mg im q8h. it is reconstituted with 2.5 ml of sterile water to provide 330 mg/ml. how many milliliters will you administer? 18. the physician orders ticar 400 mg im q4h. it is reconstituted with 2 ml of sterile water to provide 1 g/2.6 ml. how many milliliters will you administer? 19. the physician orders carbenicillin 500 mg im q8h. it is reconstituted with 5 ml of diluent to provide 1 g/3 ml. how many milliliters will you administer? 20. the physician orders penicillin g 400,000 u im q4h. it is reconstituted with 1.6 ml of sterile water to provide 500,000 u/ml. how many milliliters will you administer?

Explanation:

Step1: Set up proportion

For each problem, we use the proportion $\frac{\text{Desired dose}}{\text{Concentration}}=\text{Volume to administer}$.

Step2: Convert units if needed

In problems where the units of the desired dose and the concentration's units don't match (e.g., when concentration is in g/mL and dose is in mg), convert to the same unit. 1 g = 1000 mg.

Step3: Solve for volume

For problem 17:
The desired dose is 500 mg and the concentration is 330 mg/mL. Using the formula $\text{Volume}=\frac{500}{330}\approx1.52$ mL.
For problem 18:
First convert 1 g to 1000 mg. The concentration is 1000 mg/2.6 mL and the desired dose is 400 mg. Then $\text{Volume}=\frac{400\times2.6}{1000}=1.04$ mL.
For problem 19:
Convert 1 g to 1000 mg. The concentration is 1000 mg/3 mL and the desired dose is 500 mg. So $\text{Volume}=\frac{500\times3}{1000}=1.5$ mL.
For problem 20:
The desired dose is 400000 U and the concentration is 500000 U/mL. Then $\text{Volume}=\frac{400000}{500000}=0.8$ mL.

Answer:

1. Approximately 1.52 mL
2. 1.04 mL
3. 1.5 mL
4. 0.8 mL