A pharmacy technician is preparing a mouthwash with a 1:2:1 ratio of diphenhydramine, lidocaine, and aluminium hydroxide. If the solution contains 60 mL of lidocaine, how many mL of diphenhydramine should be compounded?

To determine the correct amount of diphenhydramine to be compounded, understanding the 1:2:1 ratio is essential. The ratio indicates that for every part of diphenhydramine, there are two parts of lidocaine and one part of aluminium hydroxide.

Given that the pharmacy technician has 60 mL of lidocaine, we can deduce the quantities of the other components based on the ratio. Since lidocaine is two parts in the ratio, we recognize that 60 mL represents those two parts. To find out the volume of one part, we divide the volume of lidocaine by 2:

60 mL (lidocaine) ÷ 2 parts = 30 mL per part.

Now that we have established that each part in the ratio corresponds to 30 mL, we can identify the volume of diphenhydramine, which corresponds to one part. Therefore, to match the 1:2:1 ratio:

Diphenhydramine = 30 mL (one part).

Consequently, the required amount of diphenhydramine to be compounded is 30 mL, confirming that this choice aligns precisely with the established ratio of the components in the mouthwash formulation.