Question

question 12

a pharmacy technician is preparing a prescription for a mouthwash that contains a 1:2:1 ratio of diphenhydramine, lidocaine, and aluminum hydroxide. if the solution contains 60 ml of lidocaine, how many ml of diphenhydramine should the technician compound?

60 ml
15 ml
30 ml
20 ml

Explanation:

Identify the given ratio and values

Using the Compounding Ratios knowledge point
The ratio of diphenhydramine to lidocaine to aluminum hydroxide is:

$$ 1 : 2 : 1 $$

The volume of lidocaine is:

$$ V_{\text{lidocaine}} = 60\text{ mL} $$

Set up the proportion for diphenhydramine

Using the Compounding Ratios knowledge point

$$ \frac{V_{\text{diphenhydramine}}}{V_{\text{lidocaine}}} = \frac{1}{2} $$

Calculate the volume of diphenhydramine

Using the Compounding Ratios knowledge point

$$ V_{\text{diphenhydramine}} = 60\text{ mL} \times \frac{1}{2} = 30\text{ mL} $$

Answer:

• (A) 60 mL
• (B) 15 mL
• (C) 30 mL (Correct answer)
• (D) 20 mL