74. A prescription order is written for 40 mg of a drug. It is available in a 10 mL vial with a concentration of 25 mg/mL. How many mL are needed for the ordered dose?
Answer: B
1.6 mL are needed for the ordered dose.
To calculate the volume required for a 40 mg dose of a drug with a concentration of 25 mg/mL, divide the dose by the concentration: 40 mg ÷ 25 mg/mL = 1.6 mL.
A) 0.625
This option is incorrect because it represents a volume too small to deliver the prescribed dose. If 0.625 mL were used, it would only provide 15.625 mg (0.625 mL × 25 mg/mL), which falls short of the required 40 mg.
B) 1.6
This option is correct as it accurately reflects the volume needed to achieve the prescribed dose. By calculating 40 mg divided by the concentration of 25 mg/mL, the result is indeed 1.6 mL, which is the correct amount needed.
C) 6.25
This choice is incorrect because it suggests a much larger volume than necessary. If 6.25 mL were given, it would provide 156.25 mg (6.25 mL × 25 mg/mL), significantly exceeding the required 40 mg.
D) 16
This option is incorrect as it indicates an excessively high volume. Administering 16 mL would result in delivering 400 mg (16 mL × 25 mg/mL), which is far beyond the prescribed dose of 40 mg.
Conclusion
The correct answer, 1.6 mL, is derived from the appropriate calculation based on the drug's concentration. All other options either underestimate or overestimate the volume required, demonstrating a clear understanding of dosage calculations is essential in medication administration.