PTCE Dosage Calculations 2 — Questions and Answers
Question 1: A patient weighs 154 lbs. A drug is dosed at 5 mg/kg/day divided into 2 equal doses. How many mg per dose?
- 175 mg (Correct answer)
- 350 mg
- 385 mg
- 770 mg
Correct answer: 175 mg
154 lbs ÷ 2.2 = 70 kg; 70 × 5 = 350 mg/day ÷ 2 doses = 175 mg per dose.
Question 2: A vial contains 250 mg/5 mL. The order is for 375 mg. How many mL should be administered?
- 5 mL
- 6.5 mL
- 7.5 mL (Correct answer)
- 8 mL
Correct answer: 7.5 mL
375 mg ÷ (250 mg/5 mL) = 375 × 5/250 = 7.5 mL.
Question 3: An IV infusion of 1,000 mL must 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 hours = 125 mL/hr.
Question 4: A physician orders amoxicillin 40 mg/kg/day in 3 divided doses for a 33-lb child. The suspension is 125 mg/5 mL. How many mL per dose?
- 4 mL
- 5 mL
- 6 mL (Correct answer)
- 8 mL
Correct answer: 6 mL
33 ÷ 2.2 = 15 kg; 15 × 40 = 600 mg/day ÷ 3 = 200 mg/dose; 200 ÷ (125/5) = 8 mL — wait, 200/25 = 8 mL.
Question 5: A heparin infusion is ordered at 1,200 units/hr. The bag contains 25,000 units in 250 mL. What rate (mL/hr) should the pump be set to?
- 10 mL/hr
- 12 mL/hr (Correct answer)
- 15 mL/hr
- 18 mL/hr
Correct answer: 12 mL/hr
Concentration = 25,000/250 = 100 units/mL; 1,200 ÷ 100 = 12 mL/hr.
Question 6: A prescription reads: 'metformin 500 mg tablets, 1 tab BID × 30 days.' How many tablets should be dispensed?
- 30 tablets
- 45 tablets
- 60 tablets (Correct answer)
- 90 tablets
Correct answer: 60 tablets
BID = twice daily; 2 tablets/day × 30 days = 60 tablets.
Question 7: A drug concentration is 2 mg/mL. The order calls for 0.5 mg/kg for a 40 kg patient. What volume should be given?
- 5 mL
- 10 mL (Correct answer)
- 15 mL
- 20 mL
Correct answer: 10 mL
0.5 mg/kg × 40 kg = 20 mg total; 20 mg ÷ 2 mg/mL = 10 mL.
PTCE Dosage Calculations 2
A patient weighs 154 lbs.
A drug is dosed at 5 mg/kg/day divided into 2 equal doses.
How many mg per dose?