M M Skills Problem Example and Solution: You have been
asked to make 500 mL of 50% dexamethasone
solution from a 90% dexamethasone stock solution.
What volume of the stock lidocaine and what volume
of water do you need?
M

278 ml of lidocaine and 222 ml of water are needed to make the solution.

Explanation:

Given that I have been asked to make 500 mL of 50% dexamethasone solution from a 90% dexamethasone stock solution, to determine what volume of the stock lidocaine and what volume of water do I need, I need to perform the following calculation:

100 x 0.90 + 0 x 0 = 90

90 x 0.90 + 10 x 0 = 81

80 x 0.90 + 20 x 0 = 72

60 x 0.90 + 40 x 0 = 54

55 x 0.90 + 45 x 0 = 49.5

56 x 0.90 + 44 x 0 = 50.4

55.5 x 0.90 + 44.5 x 0 = 49.95

55.6 x 0.90 + 44.4 x 0 = 50.04

500 x 0.556 = 278

Thus, 278 ml of lidocaine and 222 ml of water are needed to make the solution.

hmu

Explanation: