Challenge yourself to the following dosage and calculation questions
Below are sample questions from this exam to help you understand the content and format.
Q1: A nurse is preparing to administer calcium carbonate 3.9 g PO daily in equally divided doses every 12 hr. Available is calcium carbonate 650 mg tablets. How many tablets should the nurse administer per dose? (Round the answer to the nearest whole number. Use a leading zero if it applies. Do not use a trailing zero.)
Answer Choices:
Step 1: Convert the ordered dose from grams to milligrams
Formula:
mg = g × 1,000
Calculation:
3.9 g × 1,000 = 3,900 mg
Step 2: Divide the total daily dose by number of doses per day
Doses per day:
Every 12 hr = 2 doses/day
Calculation:
3,900 mg ÷ 2 = 1,950 mg per dose
Step 3: Use the formula to calculate number of tablets per dose
Formula:
Tablets = Dose per administration ÷ Tablet strength
Calculation:
Tablets = 1,950 ÷ 650 = 3 tablets
Step 4: Round the final answer to the nearest whole number
Rounded Tablets:
3 tablets
Final Answer:
3 tablets
Educational Insight
This calculation involves unit conversion, dose division, and tablet quantification—all of which are critical for accurate medication administration. Calcium carbonate is often prescribed in large doses and dividing it evenly ensures consistent absorption and therapeutic effect. By converting grams to milligrams, dividing the daily dose, and matching it to tablet strength, nurses ensure both the safety and efficacy of treatment. Rounding to the nearest whole number is essential when tablets cannot be split accurately.
Q2: A nurse is preparing to administer gentamicin 1 mg/kg 1M to a client who weighs 154 lb. Available is gentamicin solution 40 mg/mL. How many mL should the nurse administer? (Round the answer to the nearest tenth. Use a leading zero if it applies. Do not use a trailing zero.)
Answer Choices:
Step 1: Convert the client's weight from pounds to kilograms
Formula:
kg = lb ÷ 2.2
Calculation:
kg = 154 ÷ 2.2 = 70 kg
Step 2: Calculate the total dose required in mg
Formula:
Dose (mg) = Weight (kg) × Dose per kg
Calculation:
Dose = 70 × 1 = 70 mg
Step 3: Use the concentration to calculate the volume to administer
Formula:
Volume (mL) = Dose (mg) ÷ Concentration (mg/mL)
Calculation:
Volume = 70 ÷ 40 = 1.75 mL
Step 4: Round the final answer to the nearest tenth
Rounded Volume:
1.8 mL
Final Answer:
1.8 mL
Educational Insight
Gentamicin is an aminoglycoside antibiotic with a narrow therapeutic index, making accurate, weight-based dosing essential to prevent toxicity, especially nephrotoxicity and ototoxicity. This calculation demonstrates a stepwise approach: converting weight, calculating the appropriate dose, and adjusting based on the supplied concentration. Rounding to the nearest tenth is critical in IM administration to maintain both accuracy and safety.
Q3: A nurse is preparing to administer cefazolin 250 mg 1M to a client. Available is cefazolin powder for injection 500 mg vial. The nurse reconstitutes the powder with 2 mL of sterile water for a concentration of 225 mg/mL. How many mL should the nurse administer? (Round the answer to the nearest tenth. Use a leading zero if it applies. Do not use a trailing zero.)
Answer Choices:
Step 1: Identify the ordered dose and the reconstituted concentration
Ordered dose = 250 mg
Available concentration after reconstitution = 225 mg/mL
Step 2: Use the formula to calculate volume to administer
Formula:
Volume (mL) = Dose (mg) ÷ Concentration (mg/mL)
Calculation:
Volume = 250 ÷ 225 = 1.111… mL
Step 3: Round the final answer to the nearest tenth
Rounded Volume:
1.1 mL
Final Answer:
1.1 mL
Educational Insight
Reconstituting powdered medications like cefazolin requires careful attention to the resulting concentration, as it directly impacts dosing accuracy. This question highlights the importance of dividing the prescribed dose by the concentration obtained after reconstitution. Since IM injections require precision and typically involve small volumes, rounding to the nearest tenth ensures both accuracy and safe administration. Proper technique in reconstitution and dose calculation helps ensure effective treatment and minimizes complications.
Q4: A nurse is preparing to administer quinapril 20 mg PO. Available is quinapril 40 mg tablets. How many tablets should the nurse administer? (Round the answer to the nearest tenth. Use a leading zero if it applies. Do not use a trailing zero.)
Answer Choices:
Step 1: Identify the ordered dose and available tablet strength
Ordered dose = 20 mg
Available tablet strength = 40 mg/tablet
Step 2: Use the formula to calculate number of tablets to administer
Formula:
Tablets = Dose (mg) ÷ Tablet strength (mg/tablet)
Calculation:
Tablets = 20 ÷ 40 = 0.5 tablets
Step 3: Round the final answer to the nearest tenth
Rounded Tablets:
0.5 tablets
Final Answer:
0.5 tablets
Educational Insight
Quinapril is an ACE inhibitor used to treat hypertension and heart failure, and it is essential to administer the exact dose prescribed to prevent hypotension or insufficient therapeutic effect. By dividing the prescribed dose by the available tablet strength, nurses determine the correct portion of a tablet to administer. Rounding to the nearest tenth is standard for medications that can be safely split, ensuring accurate dosing without requiring a full tablet.
Q5: A nurse is preparing to administer digoxin 0.15 mg PO. Available is digoxin elixir 0.05 mg/mL. How many mL should the nurse administer? (Round the answer to the nearest whole number. Use a leading zero if it applies. Do not use a trailing zero.)
Answer Choices:
Step 1: Identify the ordered dose and available concentration
Step 2: Use the formula to calculate volume to administer
Formula:
Volume (mL) = Dose (mg) ÷ Concentration (mg/mL)
Calculation:
Volume = 0.15 ÷ 0.05 = 3 mL
Step 3: Round the final answer to the nearest whole number
Rounded Volume:
3 mL
Final Answer:
3 mL
Educational Insight
Digoxin is a cardiac glycoside with a narrow therapeutic range, often prescribed in pediatric and geriatric populations in liquid form for more accurate dosing. Understanding how to calculate volume from the concentration provided ensures safe and effective administration. Since the elixir is in mg/mL, the nurse must correctly divide the dose by the concentration. Rounding to a whole number is appropriate when the calculation results in an exact value, as seen here.
