NCLEX: Drug Dosage Calculation Exam 10

EXPLANATION

✔Solution:

Understanding the Problem:

Nurse Jackson must administer an intramuscular injection of lorazepam. The ordered dose is 3 mg, and the available injection has a concentration of 4 mg per mL. We need to calculate the volume in mL that provides 3 mg.

Step-by-Step Calculation:

1. Identify the given values:

• Ordered dose: 3 mg
• Concentration: 4 mg per 1 mL

2. Set up the conversion using dimensional analysis:

Volume required = 3 mg × (1 mL / 4 mg)

• The "mg" units cancel, leaving the result in mL.

3. Perform the calculation:

• 3 mg ÷ 4 mg/mL = 0.75 mL, which rounds to approximately 0.8 mL

Final Answer:

• Nurse Jackson should prepare 0.8 mL of the lorazepam injection.

ANSWER: 0.8 mL

Simplified recap: Divide 3 mg by the concentration (4 mg/mL) to obtain 0.75 mL, which rounds to 0.8 mL.

EXPLANATION

✔Solution:

Understanding the Problem:

Nurse Brown must administer 125 mg of methylprednisolone sodium succinate as an IV push dose. The available medication has a concentration of 40 mg per mL. We need to determine how many milliliters will provide a 125 mg dose.

Step-by-Step Calculation:

1. Identify the given values:

• Ordered dose: 125 mg
• Concentration: 40 mg per mL

2. Set up the conversion using dimensional analysis:

Volume required = 125 mg × (1 mL / 40 mg)

• The "mg" units cancel out, leaving the result in mL.

3. Perform the calculation:

• 125 mg ÷ 40 mg/mL = 3.125 mL, which rounds to approximately 3.1 mL

4. Final Answer:

• Nurse Brown should prepare 3.1 mL of the methylprednisolone sodium succinate solution for each dose.

ANSWER: 3.1 mL

Simplified recap: Divide 125 mg by 40 mg/mL to get 3.125 mL, which rounds to 3.1 mL.

EXPLANATION

✔Solution:

Understanding the Problem:

Nurse Reed is administering an IV heparin infusion at a rate of 11 mL per hour using microdrip tubing, which typically has a drop factor of 60 drops per mL. We need to determine the drip rate in drops per minute.

Step-by-Step Calculation:

1. Convert the infusion rate from mL per hour to mL per minute:

• 11 mL/hour ÷ 60 minutes/hour = 0.1833 mL/min

2. Convert the mL per minute rate to drops per minute using the drop factor:

• 0.1833 mL/min × 60 drops/mL = 11 drops/min

3. Final Answer:

• Nurse Reed should manually regulate the infusion to deliver 11 drops per minute.

ANSWER: 11 drops per minute

Simplified recap: 11 mL/hour equals 0.1833 mL/min; multiplying 0.1833 mL/min by 60 drops/mL yields 11 drops per minute.

EXPLANATION

✔Solution:

Understanding the Problem:

Nurse Green must administer 100 mL of ranitidine in D5W over 45 minutes using IV tubing with a drop factor of 15 drops per mL. We need to calculate the drip rate in drops per minute.

Step-by-Step Calculation:

1. Calculate the infusion rate in mL per minute:

• Total volume = 100 mL
• Total time = 45 minutes
• Infusion rate = 100 mL ÷ 45 min ≈ 2.22 mL/min

2. Convert the mL/min rate to drops per minute using the drop factor:

• Drip rate = 2.22 mL/min × 15 drops/mL
• 2.22 × 15 ≈ 33.33 drops/min

3. Rounding:

• Rounded to the nearest whole number, the drip rate is approximately 33 drops per minute.

Final Answer:

• Nurse Green should set the drip rate to 33 drops per minute.

ANSWER: 33 drops per minute

Simplified recap: Divide 100 mL by 45 minutes to get about 2.22 mL/min, then multiply by the drop factor of 15 to obtain approximately 33 drops per minute.

EXPLANATION

✔Solution:

Understanding the Problem:

Nurse Adams must administer 50 mg of phenobarbital elixir by mouth. The elixir is available in a concentration of 20 mg per 5 mL. The task is to determine how many milliliters of the elixir will provide a 50 mg dose.

Step-by-Step Calculation:

1. Determine the concentration in mg per mL:

• 20 mg is contained in 5 mL.
• Concentration = 20 mg ÷ 5 mL = 4 mg/mL

2. Calculate the required volume for a 50 mg dose:

• Volume = Ordered dose ÷ Concentration
• Volume = 50 mg ÷ 4 mg/mL = 12.5 mL

3. Final Answer:

• Nurse Adams should administer 12.5 mL of the phenobarbital elixir.

ANSWER: 12.5 mL

Simplified recap: With a concentration of 4 mg/mL, dividing the 50 mg ordered dose by 4 mg/mL yields 12.5 mL.

EXPLANATION

✔Solution:

Understanding the Problem:

Mrs. Murphy's psyllium hydrophilic mucilloid should be mixed with 180 mL of water or juice. Since she only has standard US measuring cups, we need to convert 180 mL to cups. The standard conversion is 1 cup = 240 mL.

Step-by-Step Calculation:

1. Set up the conversion:

• 1 cup = 240 mL
• To find the number of cups for 180 mL, use:
  Number of cups = 180 mL ÷ 240 mL per cup

2. Perform the calculation:

• 180 ÷ 240 = 0.75 cups

3. Convert the decimal to a fraction:

• 0.75 cups = 3/4 cup

Final Answer:

• Nurse Scott should instruct Mrs. Murphy to measure 3/4 cup of water or juice for each dose.

ANSWER: 3/4 cup

Simplified recap: Since 1 cup is 240 mL, 180 mL is 180/240 = 0.75 cups, which is equivalent to 3/4 cup.

EXPLANATION

✔Solution:

Understanding the Problem:

Nurse Ford must administer 50 mL of piperacillin/tazobactam in D5W over 20 minutes using IV tubing with a drop factor of 15 drops per mL. The goal is to calculate the drip rate in drops per minute.

Step-by-Step Calculation:

1. Calculate the infusion rate in mL per minute:

• Total volume = 50 mL
• Total time = 20 minutes
• Infusion rate = 50 mL ÷ 20 minutes = 2.5 mL/min

2. Convert the infusion rate to drops per minute:

• Drop factor = 15 drops per mL
• Drip rate = 2.5 mL/min × 15 drops/mL = 37.5 drops/min

3. Rounding:

• Rounded to the nearest whole number, the drip rate is approximately 38 drops per minute.

Final Answer:

• Nurse Ford should set the drip rate to 38 drops per minute.

ANSWER: 38 drops per minute

Simplified recap: Divide 50 mL by 20 minutes to get 2.5 mL/min, then multiply by the drop factor of 15 to obtain 37.5 drops/min, which rounds to 38 drops/min.

EXPLANATION

✔Solution:

Understanding the Problem:

Nurse Carter must infuse 1,000 mL of dextrose in water over 24 hours using IV tubing with a drop factor of 60 drops per mL (gtt/mL). The goal is to calculate how many drops per minute (gtt/min) should be delivered to ensure the IV fluid runs at the correct rate.

Step-by-Step Solution:

1. Convert total infusion time to minutes:

• 24 hours = 24 × 60 = 1,440 minutes

2. Apply the drop factor formula:

Rate (gtt/min) = (Total volume in mL ÷ Total time in minutes) × Drop factor (gtt/mL)

• Total volume = 1,000 mL
• Total time = 1,440 minutes
• Drop factor = 60 gtt/mL

3. Perform the calculation and cancel units:

• (1,000 mL ÷ 1,440 min) × 60 gtt/mL
• = (1,000 × 60) ÷ 1,440 = 60,000 ÷ 1,440 ≈ 41.7 gtt/min
• Rounded to nearest whole number ≈ 42 gtt/min

4. Final answer:

• The drip rate should be set to 42 drops per minute.

ANSWER: 42 drops per minute

Simplified recap: Divide 1,000 mL by the total infusion time (1,440 minutes), then multiply by the drop factor (60 gtt/mL). The result is approximately 42 gtt/min.

EXPLANATION

✔Solution:

Understanding the Problem:

Mr. Campbell’s doctor has increased his daily warfarin dose to 7.5 mg. He has warfarin 5 mg tablets. We need to determine how many tablets he should take each day to achieve the 7.5 mg dose.

Step-by-Step Calculation:

1. Identify the given values:

• Ordered dose: 7.5 mg/day
• Tablet strength: 5 mg per tablet

2. Set up the conversion:

Number of tablets = 7.5 mg × (1 tablet / 5 mg)

• The "mg" units cancel out, leaving the result in tablets.

3. Perform the calculation:

• 7.5 ÷ 5 = 1.5 tablets

4. Final Answer:

• Mr. Campbell should take 1.5 tablets daily to achieve the prescribed dose.

ANSWER: 1.5 tablets

Simplified recap: Dividing the prescribed dose (7.5 mg) by the tablet strength (5 mg per tablet) results in 1.5 tablets.

EXPLANATION

✔Solution:

Understanding the Problem:

Mrs. Lewis is prescribed captopril 6.25 mg to be taken orally twice a day. The pharmacy dispensed captopril 25 mg scored tablets. We need to determine the fraction of a tablet that provides a 6.25 mg dose.

Step-by-Step Calculation:

1. Identify the given values:

• Ordered dose: 6.25 mg
• Tablet strength: 25 mg per tablet

2. Set up the conversion using dimensional analysis:

Number of tablets = 6.25 mg × (1 tablet / 25 mg)

• The "mg" units cancel, leaving the result in tablets.

3. Perform the calculation:

• 6.25 ÷ 25 = 0.25 tablet

4. Final Answer:

• Mrs. Lewis should take 1/4 tablet for each dose.

ANSWER: 1/4 tablet

Simplified recap: Dividing the prescribed dose (6.25 mg) by the tablet strength (25 mg) gives 0.25 tablet, which is equivalent to 1/4 of a tablet.