The stock suspension for amoxicillin contains 250 mg per 5 mL. If a doctor orders 1.5 g by mouth, how many milliliters should be administered?

The stock suspension for amoxicillin contains 250 mg per 5 mL. If a doctor orders 1.5 g by mouth, how many milliliters should be administered?

• A. 15 mL
• B. 50 mL
• C. 30 mL
• D. 60 mL

Answer: (C)

The key idea is to use the suspension’s concentration to turn the prescribed amount into a volume. The suspension has 250 mg in 5 mL, which is 50 mg per 1 mL. The order is 1.5 g, which equals 1500 mg. Divide the dose by the concentration: 1500 mg ÷ 50 mg/mL = 30 mL. So 30 mL is needed. A quick check: 30 mL × 50 mg/mL = 1500 mg, matches the order. The other volumes would give too little or too much: 15 mL gives 750 mg, 50 mL gives 2500 mg, and 60 mL gives 3000 mg.

The key idea is to use the suspension’s concentration to turn the prescribed amount into a volume. The suspension has 250 mg in 5 mL, which is 50 mg per 1 mL. The order is 1.5 g, which equals 1500 mg. Divide the dose by the concentration: 1500 mg ÷ 50 mg/mL = 30 mL. So 30 mL is needed. A quick check: 30 mL × 50 mg/mL = 1500 mg, matches the order. The other volumes would give too little or too much: 15 mL gives 750 mg, 50 mL gives 2500 mg, and 60 mL gives 3000 mg.