A medication is available as 250 mg per 5 mL suspension. A prescriber orders 375 mg. How many milliliters should be administered?
- A.6.5 mL
- B.7.5 mL
- C.8 mL
- D.5 mL
Show answer & rationale
Correct answer
B. 7.5 mL
Rationale
B is correct: Set up the proportion: 250 mg / 5 mL = 375 mg / x mL. Cross-multiply: 250x = 1875. Divide: x = 1875 ÷ 250 = 7.5 mL. A is incorrect: 6.5 mL would deliver 325 mg (6.5 × 50 mg/mL), which is less than the ordered dose. C is incorrect: 8 mL would deliver 400 mg, which exceeds the ordered dose. D is incorrect: 5 mL delivers only 250 mg, the available concentration, not the ordered 375 mg.
Key concepts
Dosage calculationProportion and ratioUnit conversion