Saudi Prometric Nursing Pharmacology and Drug Calculations 1 — Questions and Answers
Question 1: A patient weighing 70 kg is prescribed gentamicin 5 mg/kg IV once daily. What is the correct dose?
- 350 mg (Correct answer)
- 500 mg
- 250 mg
- 420 mg
Correct answer: 350 mg
Dose = weight (kg) × dose/kg = 70 kg × 5 mg/kg = 350 mg. Weight-based dosing of aminoglycosides like gentamicin is standard practice to optimize therapeutic efficacy while minimizing nephrotoxicity and ototoxicity.
Question 2: A nurse is preparing to administer heparin 5,000 units subcutaneously. The available vial contains 10,000 units/mL. How many mL should be administered?
- 0.5 mL (Correct answer)
- 1 mL
- 0.25 mL
- 2 mL
Correct answer: 0.5 mL
Volume = desired dose / available concentration = 5,000 units / 10,000 units per mL = 0.5 mL. This is a standard dosage calculation using the ratio method or the formula D/H × V.
Question 3: A patient is prescribed morphine 4 mg IV. The available solution contains 10 mg in 5 mL. How many mL should the nurse administer?
- 2 mL (Correct answer)
- 0.4 mL
- 4 mL
- 8 mL
Correct answer: 2 mL
Concentration = 10 mg/5 mL = 2 mg/mL. Volume = 4 mg ÷ 2 mg/mL = 2 mL. Alternatively: (4 mg / 10 mg) × 5 mL = 2 mL.
Question 4: A nurse is administering an IV infusion of 1,000 mL normal saline over 8 hours. Using a drip set of 20 drops/mL, what is the correct drip rate in drops per minute (dpm)?
- 42 dpm (Correct answer)
- 20 dpm
- 50 dpm
- 125 dpm
Correct answer: 42 dpm
Drip rate = (Volume in mL × Drop factor) / Time in minutes = (1,000 × 20) / (8 × 60) = 20,000 / 480 = 41.67 ≈ 42 dpm. This standard formula calculates gravity IV infusion rates.
Question 5: A patient is prescribed dopamine 400 mg in 250 mL D5W to infuse at 5 mcg/kg/min. The patient weighs 80 kg. What is the infusion rate in mL/hr?
- 15 mL/hr (Correct answer)
- 30 mL/hr
- 7.5 mL/hr
- 60 mL/hr
Correct answer: 15 mL/hr
Step 1: Dose in mcg/min = 5 × 80 = 400 mcg/min. Step 2: Convert to mg/min: 400/1,000 = 0.4 mg/min. Step 3: Concentration = 400 mg/250 mL = 1.6 mg/mL. Step 4: mL/min = 0.4/1.6 = 0.25 mL/min. Step 5: mL/hr = 0.25 × 60 = 15 mL/hr.
Question 6: A nurse is administering IV ampicillin 500 mg in 100 mL normal saline to be infused over 30 minutes. Using a microdrip set (60 drops/mL), what is the drip rate?
- 200 dpm (Correct answer)
- 100 dpm
- 50 dpm
- 120 dpm
Correct answer: 200 dpm
Drip rate = (100 mL × 60 drops/mL) / 30 minutes = 6,000 / 30 = 200 dpm. With microdrip sets, mL/hr equals drops per minute (since 60 drops/mL ÷ 60 min = 1). So 100 mL/0.5 hr = 200 mL/hr = 200 dpm.
Saudi Prometric Nursing Pharmacology and Drug Calculations 1
A patient weighing 70 kg is prescribed gentamicin 5 mg/kg IV once daily.
What is the correct dose?