A cough syrup is ordered as 0.4 g every 4 hours. The syrup strength is 100 mg per 5 mL. How many teaspoons should be given per dose?

A cough syrup is ordered as 0.4 g every 4 hours. The syrup strength is 100 mg per 5 mL. How many teaspoons should be given per dose?

• A. 2 tsp
• B. 3 tsp
• C. 4 tsp
• D. 5 tsp

Answer: (C)

Translating a mass-based order into a syrup volume using concentration is the key idea. Start by converting the ordered amount to milligrams: 0.4 g equals 400 mg. The syrup concentration is 100 mg in 5 mL, which is 20 mg per mL. To deliver 400 mg, you need 400 mg ÷ 20 mg/mL = 20 mL of syrup. Since 1 teaspoon is 5 mL, 20 mL equals 20 ÷ 5 = 4 teaspoons per dose. So the correct dose is 4 teaspoons.

Translating a mass-based order into a syrup volume using concentration is the key idea. Start by converting the ordered amount to milligrams: 0.4 g equals 400 mg. The syrup concentration is 100 mg in 5 mL, which is 20 mg per mL. To deliver 400 mg, you need 400 mg ÷ 20 mg/mL = 20 mL of syrup. Since 1 teaspoon is 5 mL, 20 mL equals 20 ÷ 5 = 4 teaspoons per dose. So the correct dose is 4 teaspoons.