78. A 200 g compounded ointment contains 10 g of active ingredient. Which of the following strengths should the pharmacy technician place on the prescription label?
Answer: B
The strength of the compounded ointment is 5%.
The compounded ointment contains 10 g of active ingredient in a total of 200 g of ointment. To determine the strength, the active ingredient amount is divided by the total weight and then multiplied by 100, resulting in a strength of 5%.
A) 10%
This option is incorrect because a 10% strength would imply that there are 10 g of active ingredient in every 100 g of ointment. However, the actual calculation shows that 10 g in 200 g is a 5% strength.
B) 5%
This option is correct as it accurately reflects the proportion of active ingredient in the ointment. The calculation (10 g active ingredient / 200 g total ointment) x 100 equals 5%, making this the proper strength to place on the prescription label.
C) 20%
This option is incorrect as it suggests that there would be 20 g of active ingredient in every 100 g of ointment. Given the total amount of active ingredient (10 g) and the total weight (200 g), this strength is mathematically impossible.
D) 25%
This option is also incorrect because a 25% strength would indicate that there are 25 g of active ingredient per 100 g of ointment, which is not supported by the provided quantities. The actual strength is much lower at 5%.
Conclusion
The correct strength of 5% accurately represents the concentration of active ingredient in the compounded ointment, calculated through direct proportion. All other options misrepresent the relationship between the active ingredient and the total weight, leading to incorrect interpretations of the formulation's strength.