PTCE Dosage Calculations 3 — Questions and Answers
Question 1: An IV is infusing at 50 mL/hr using a 15 gtt/mL drip set. What is the drop rate in gtt/min?
- 10 gtt/min
- 12.5 gtt/min (Correct answer)
- 15 gtt/min
- 20 gtt/min
Correct answer: 12.5 gtt/min
50 mL/hr × 15 gtt/mL ÷ 60 min/hr = 12.5 gtt/min.
Question 2: A topical cream is prescribed as 'apply TID to affected area, 30g tube.' At an estimated 1g per application, how many days will the tube last?
- 7 days
- 10 days (Correct answer)
- 15 days
- 30 days
Correct answer: 10 days
TID = 3 times daily; 30g ÷ 3g/day = 10 days.
Question 3: Convert 0.125 mg to micrograms (mcg).
- 0.000125 mcg
- 1.25 mcg
- 12.5 mcg
- 125 mcg (Correct answer)
Correct answer: 125 mcg
1 mg = 1,000 mcg; 0.125 × 1,000 = 125 mcg.
Question 4: A patient needs a 2% lidocaine solution. How many mg of lidocaine are in 10 mL?
- 2 mg
- 20 mg
- 200 mg (Correct answer)
- 2,000 mg
Correct answer: 200 mg
2% = 2 g/100 mL = 20 mg/mL; 20 mg/mL × 10 mL = 200 mg.
Question 5: A physician orders phenobarbital 3 mg/kg for a child weighing 44 lbs. Tablets are 15 mg. How many tablets are needed?
- 2 tablets
- 4 tablets
- 6 tablets (Correct answer)
- 8 tablets
Correct answer: 6 tablets
44 ÷ 2.2 = 20 kg; 20 × 3 mg = 60 mg; 60 ÷ 15 mg/tab = 4 tablets.
Question 6: A 500 mL bag with 20 mEq KCl must infuse in 4 hours. What is the infusion rate?
- 100 mL/hr
- 125 mL/hr (Correct answer)
- 150 mL/hr
- 200 mL/hr
Correct answer: 125 mL/hr
500 mL ÷ 4 hr = 125 mL/hr.
Question 7: A prescription calls for ibuprofen suspension 100 mg/5 mL; dose is 10 mg/kg for a 22 kg child. How many mL per dose?
- 5.5 mL
- 11 mL (Correct answer)
- 16.5 mL
- 22 mL
Correct answer: 11 mL
22 kg × 10 mg/kg = 220 mg; 220 ÷ (100/5) = 220 ÷ 20 = 11 mL.
PTCE Dosage Calculations 3
An IV is infusing at 50 mL/hr using a 15 gtt/mL drip set.
What is the drop rate in gtt/min?