Pharmacy Dosage Calculations 2 — Questions and Answers
Question 1: A physician orders 500 mg of amoxicillin. The available stock is 250 mg/5 mL. How many mL should be dispensed per dose?
- 5 mL
- 10 mL (Correct answer)
- 15 mL
- 20 mL
Correct answer: 10 mL
Using the ratio: 250 mg/5 mL = 500 mg/x. Solving: x = (500 × 5) / 250 = 10 mL.
Question 2: A patient needs 0.4 mg of clonidine. The available tablets are 0.2 mg each. How many tablets should be given?
- 0.5 tablet
- 1 tablet
- 2 tablets (Correct answer)
- 4 tablets
Correct answer: 2 tablets
0.4 mg ÷ 0.2 mg/tablet = 2 tablets.
Question 3: An IV infusion of 1,000 mL is to run over 8 hours. What is the flow rate in mL/hr?
- 100 mL/hr
- 115 mL/hr
- 125 mL/hr (Correct answer)
- 150 mL/hr
Correct answer: 125 mL/hr
1,000 mL ÷ 8 hr = 125 mL/hr.
Question 4: A prescription calls for 1.5 g of a drug. How many milligrams is this?
- 15 mg
- 150 mg
- 1,500 mg (Correct answer)
- 15,000 mg
Correct answer: 1,500 mg
1 g = 1,000 mg, so 1.5 g = 1,500 mg.
Question 5: A technician needs to prepare 240 mL of a 2% solution using a 10% stock solution. How many mL of stock solution are needed?
- 24 mL
- 36 mL
- 48 mL (Correct answer)
- 60 mL
Correct answer: 48 mL
Using alligation or C1V1 = C2V2: 10% × V1 = 2% × 240 mL → V1 = 480/10 = 48 mL.
Question 6: A drop factor is 15 gtts/mL and the ordered rate is 90 mL/hr. What is the drip rate in gtts/min?
- 15 gtts/min
- 20 gtts/min
- 22.5 gtts/min (Correct answer)
- 30 gtts/min
Correct answer: 22.5 gtts/min
(90 mL/hr × 15 gtts/mL) ÷ 60 min = 1350/60 = 22.5 gtts/min.
Pharmacy Dosage Calculations 2
A physician orders 500 mg of amoxicillin.
The available stock is 250 mg/5 mL.
How many mL should be dispensed per dose?