70. Caiculator Aprescription 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 administer a dose of 40 mg from a solution that has a concentration of 25 mg/mL, you need to calculate the volume required. This is done by dividing the desired dose by the concentration, yielding 1.6 mL.
A) 0.625
This option is incorrect because if you were to use 0.625 mL at a concentration of 25 mg/mL, it would only provide 15.625 mg (0.625 mL × 25 mg/mL), which is significantly less than the required 40 mg.
B) 1.6
This option is correct. To find the required volume, you divide the ordered dose (40 mg) by the concentration (25 mg/mL). This results in 1.6 mL (40 mg ÷ 25 mg/mL = 1.6 mL), which is precisely the volume needed to deliver the ordered dose.
C) 6.25
Choosing 6.25 mL is incorrect because at a concentration of 25 mg/mL, this volume would provide 156.25 mg (6.25 mL × 25 mg/mL), which far exceeds the required dose of 40 mg.
D) 16
This option is also incorrect. Administering 16 mL would deliver an excessive amount of 400 mg (16 mL × 25 mg/mL), which is ten times greater than the prescribed dose of 40 mg.
Conclusion
The calculation confirms that 1.6 mL is indeed the correct volume needed to achieve the ordered dose of 40 mg. The other options either underdose or overdose the required amount, demonstrating that accurate calculations based on concentration are crucial in medication administration.