NEX Mathematical Calculations: Dosages and Solutions 2

Question 1

A physician orders 500 mg of amoxicillin. The available supply is 250 mg per capsule. How many capsules should the nurse administer?

Accepted Answer

2 capsules

Answer

Using the formula: Desired dose / Available dose = 500 mg / 250 mg = 2 capsules.

Question 2

A patient weighs 176 pounds. A medication is ordered at 5 mg/kg/day divided into two doses. What is the amount per dose?

Accepted Answer

200 mg

Answer

Convert pounds to kg: 176 ÷ 2.2 = 80 kg. Total daily dose: 80 × 5 = 400 mg. Divided by 2 doses: 400 ÷ 2 = 200 mg per dose.

Question 3

An IV infusion of 1,000 mL of normal saline is ordered to run over 8 hours. The drip factor is 15 gtt/mL. What is the correct flow rate in gtt/min?

Accepted Answer

31 gtt/min

Answer

Flow rate = (Volume × Drop factor) / (Time in minutes) = (1000 × 15) / (8 × 60) = 15000 / 480 = 31.25, rounded to 31 gtt/min.

Question 4

How many milliliters of a drug should be drawn up if the order is for 75 mg and the vial contains 100 mg/2 mL?

Accepted Answer

1.5 mL

Answer

Using the formula: (Desired/Available) × Volume = (75/100) × 2 = 0.75 × 2 = 1.5 mL.

Question 5

A nurse needs to prepare a 1:4 dilution of a stock solution. If the final volume needed is 200 mL, how much stock solution is required?

Accepted Answer

50 mL

Answer

A 1:4 dilution means 1 part stock to a total of 4 parts. Stock volume = Total volume / Dilution factor = 200 / 4 = 50 mL of stock solution.

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