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Medication Dosage Calculations - NCLEX Pn

  1. A 64-year-old client is prescribed potassium chloride 20 mEq PO once daily. The available liquid is potassium chloride 10 mEq/5 mL. What is the correct volume to administer per dose?
    Answer: 10 mL This question tests medication dosage calculation skills. The key calculation principle is conversion from mEq to volume using liquid concentration. The correct answer of 10 mL is calculated by (20 mEq / 10 mEq) × 5 mL = 10 mL. Choice A (5 mL) results from not multiplying; choice C (15 mL) from adding; choice D (20 mL) from doubling. The formula used is volume = (ordered / conc) × volume per conc. Dilute as needed. A transferable strategy is to use ratio: ordered mEq to available mEq as x mL to 5 mL.
  2. A 9-year-old child weighs 30 kg and is prescribed clindamycin 10 mg/kg/day10\ \text{mg/kg/day} PO divided q8h; the safe range is 88–20 mg/kg/day20\ \text{mg/kg/day}. The oral solution is 75 mg/5 mL75\ \text{mg}/5\ \text{mL}. What is the correct volume to administer per dose (round to the nearest tenth)?
    Answer: 6.7 mL per dose This question tests medication dosage calculation skills. The key calculation principle is weight-based daily dosing divided by frequency and converted to volume. The correct answer of 6.7 mL is calculated by daily dose (10 mg/kg/day × 30 kg = 300 mg/day), per dose (300 / 3 = 100 mg), volume ((100 / 75) × 5 ≈ 6.7 mL). Choice A (3.3 mL) results from halving; choice C (13.3 mL) from not dividing; choice D (10.0 mL) from misconcentration. The formula used is per dose = (mg/kg/day × weight) / doses, volume = (dose / mg) × mL. Verify safe range. A transferable strategy is to compute daily total first, divide by doses, then apply concentration ratio.
  3. A 69-year-old client with type 2 diabetes is prescribed metformin 0.5 g PO twice daily. The pharmacy supplies metformin 500 mg tablets. Convert the prescribed dosage into the available concentration (how many tablets per dose).
    Answer: 1 tablet per dose This question tests medication dosage calculation skills. The key calculation principle is unit conversion from grams to milligrams and then to number of tablets. The correct answer of 1 tablet is calculated by converting 0.5 g to 500 mg and dividing by 500 mg per tablet (500 / 500 = 1). Choice A (2 tablets) results from not converting grams; choice C (0.5 tablet) from halving; choice D (4 tablets) from misconversion. The formula used is number of tablets = (ordered dose in mg) / (mg per tablet). Ensure consistent units. A transferable strategy is to convert all doses to mg before calculating tablet count.
  4. How many milliliters (mL) should the nurse administer?
    Answer: 0.5 mL Formula: (Desired / Have) x Quantity. (25 mg / 50 mg) x 1 mL = 0.5 mL. The prescribed dose is half the available concentration, so half the volume (0.5 mL) is required.
  5. A 6-year-old child weighs 20 kg and has a fever. The provider orders ibuprofen 10 mg/kg10\ \text{mg/kg} PO q6h PRN; do not exceed 40 mg/kg/day40\ \text{mg/kg/day}. The available liquid is ibuprofen 100 mg/5 mL100\ \text{mg}/5\ \text{mL}. What is the correct volume to administer per dose?
    Answer: 10 mL This question tests medication dosage calculation skills. The key calculation principle is weight-based dosing converted to volume using the liquid concentration. The correct answer of 10 mL is calculated by determining the dose (10 mg/kg × 20 kg = 200 mg) and converting ((200 mg / 100 mg) × 5 mL = 10 mL). Choice A (5 mL) results from halving the dose; choice C (20 mL) from doubling; choice D (2.5 mL) from using half weight. The formula used is dose = mg/kg × weight, then volume = (dose / concentration) × volume per concentration. Verify the daily maximum is not exceeded. A transferable strategy is to calculate the mg dose first, then apply the ratio of available concentration to find volume.
  6. What is the correct total dose in milligrams (mg)?
    Answer: 100 mg Step 1: Convert pounds to kilograms: 44 lbs / 2.2 = 20 kg. Step 2: Calculate the dose: 20 kg x 5 mg/kg = 100 mg. Choice A (50 mg) results from using 10 kg (dividing by 4.4 instead of 2.2). Choice C (200 mg) results from using 40 kg (multiplying instead of dividing lbs by 2.2). Choice D (220 mg) results from skipping the kg conversion and multiplying 44 lbs x 5 mg directly.
  7. A 57-year-old client with pain is prescribed morphine 6 mg IM. The vial is labeled morphine 10 mg/mL. What is the correct volume to administer?
    Answer: 0.6 mL This question tests medication dosage calculation skills. The key calculation principle is dose conversion to volume using vial concentration. The correct answer of 0.6 mL is calculated by dividing 6 mg by 10 mg/mL (6 / 10 = 0.6 mL). Choice A (0.4 mL) results from using 4 mg; choice C (1.0 mL) from not dividing; choice D (1.6 mL) from miscalculation. The formula used is volume = ordered / concentration. Use appropriate syringe. A transferable strategy is to divide dose by mg per mL directly.
  8. How many milliliters (mL) should the nurse draw up in the syringe?
    Answer: 0.5 mL Formula: (Desired / Have) x Quantity. (5,000 units / 10,000 units) x 1 mL = 0.5 mL. Because heparin is a high-alert medication, any calculated volume should be independently verified by a second nurse before administration.
  9. After administering the new dose, the nurse monitors the client for a therapeutic response. Which finding indicates the medication and dosage are effective?
    Answer: The client reports that the skin infection area is less red and painful. A therapeutic effect of antibiotic treatment for a skin infection is evidenced by the resolution of the infection's hallmark signs: decreased redness, reduced pain, and improvement in local tissue appearance. These are the direct clinical outcomes that confirm the medication is working at the prescribed dose. A WBC count that remains elevated at 16,000 (A) indicates ongoing infection rather than improvement — a downward trend toward normal range would be expected with effective therapy. Tachycardia (C) is a sign of physiological stress, possibly from infection or adverse effect, and does not indicate therapeutic success. A new rash on the chest and arms (D) requires immediate clinical attention in this specific client: given the documented penicillin allergy and the known cross-reactivity between penicillins and cephalosporins, a new rash after starting cefazolin may indicate an allergic reaction, and the nurse must stop the medication and notify the PHCP — this finding is the opposite of therapeutic success.
  10. How many tablets should the nurse administer?
    Answer: 2 tablets Step 1: Convert grams to milligrams: 1 gram = 1,000 mg. Step 2: (1,000 mg / 500 mg) x 1 tablet = 2 tablets. The unit conversion from grams to milligrams is the critical first step — attempting to calculate without converting would produce a nonsensical result.
  11. How many milliliters (mL) should the nurse administer to the child? (Round to the nearest tenth.)
    Answer: 7.8 mL Using the formula: (Desired / Have) x Quantity. (250 mg / 160 mg) x 5 mL = 7.8125 mL. Rounded to the nearest tenth: 7.8 mL.
  12. A 41-year-old client with asthma is prescribed prednisone 60 mg PO daily for 5 days. The available tablets are 20 mg. How many tablets should the client receive per dose?
    Answer: 3 tablets This question tests medication dosage calculation skills. The key calculation principle is simple dose conversion to number of tablets. The correct answer of 3 tablets is calculated by dividing 60 mg by 20 mg per tablet (60 / 20 = 3). Choice A (2 tablets) results from using 30 mg; choice C (1 tablet) from not dividing; choice D (4 tablets) from miscalculation. The formula used is number of tablets = ordered / available. Confirm daily total. A transferable strategy is to use division directly for whole tablet counts.
  13. How many tablets should the nurse provide to the client?
    Answer: 2 tablets Formula: (Desired / Have) x Quantity. (0.25 mg / 0.125 mg) x 1 tablet = 2 tablets. The prescribed dose is exactly double the available tablet strength, requiring two tablets to deliver the ordered dose.
  14. What is the most appropriate action for the nurse to take regarding the medication order?
    Answer: Withhold the medication and contact the PHCP to clarify the dose. When a nurse determines that a prescribed dose falls outside the established safe dose range, the medication must be withheld and the PHCP must be contacted for clarification before any dose is given. This is a core medication safety responsibility of the LPN/VN. Administering the order as written (A and B) exposes the pediatric client to a supratherapeutic dose that could cause serious adverse effects. Giving the first dose and then seeking correction (D) is equally unsafe — the unsafe dose is the first dose, not subsequent ones. The nurse must not administer any dose that has been identified as outside the safe range without PHCP clarification and a corrected order.
  15. How many tablets should the nurse administer to the client?
    Answer: 2 tablets Using the standard dosage formula: (Desired dose / Have on hand) x Quantity. (0.5 mg / 0.25 mg) x 1 tablet = 2 tablets. Each tablet contains 0.25 mg, and two tablets are required to deliver the prescribed 0.5 mg dose.
  16. What is the client's total intake in milliliters (mL)?
    Answer: 780 mL Convert each item to mL, then sum: 4 oz juice: 4 x 30 mL = 120 mL. 6 oz water: 6 x 30 mL = 180 mL. 2 cups coffee: 2 x 240 mL = 480 mL. Total: 120 + 180 + 480 = 780 mL. Choice A (300 mL) results from adding only the ounces without converting the cups. Choice B (480 mL) reflects only the cups of coffee. Choice D (1,020 mL) results from using 300 mL per cup rather than 240 mL.
  17. A 77-year-old client is prescribed digoxin 0.125 mg PO daily. The medication available is digoxin 250 mcg tablets. Convert the prescribed dosage into the available concentration (how many tablets per dose).
    Answer: 0.5 tablet This question tests medication dosage calculation skills. The key calculation principle is unit conversion from mg to mcg and then to number of tablets. The correct answer of 0.5 tablet is calculated by converting 0.125 mg to 125 mcg and dividing by 250 mcg (125 / 250 = 0.5). Choice A (0.25 tablet) results from halving; choice C (1 tablet) from not converting; choice D (2 tablets) from doubling. The formula used is number of tablets = (ordered in mcg) / (mcg per tablet). Convert units consistently. A transferable strategy is to always convert to mcg for digoxin calculations before dividing.
  18. What is the total safe dose range in milligrams (mg) per day for this 25 kg client?
    Answer: 625 to 1,250 mg/day Using the safe dose range of 25 to 50 mg/kg/day and the client's weight of 25 kg: Minimum: 25 mg/kg x 25 kg = 625 mg/day. Maximum: 50 mg/kg x 25 kg = 1,250 mg/day. Safe range: 625 to 1,250 mg/day. Choice A uses only the per-kg numbers (25 and 50) without multiplying by weight. Choice D doubles the correct answer, a common error from misreading the weight as 50 kg.
  19. How many milliliters (mL) will the client receive in a single dose?
    Answer: 10 mL 2 teaspoons x 5 mL/teaspoon = 10 mL per dose. Choice A (2 mL) results from not applying the conversion factor. Choice B (5 mL) represents 1 teaspoon, not 2. Choice D (15 mL) represents 3 teaspoons.
  20. The PHCP clarifies the order to 300 mg IV every 8 hours (total 900 mg/day). The medication is reconstituted to a concentration of 225 mg/mL. How many mL should the nurse draw up for a 300 mg dose? (Round to the nearest tenth.)
    Answer: 1.3 mL Formula: (Desired / Have) x Quantity. (300 mg / 225 mg) x 1 mL = 1.333 mL. Rounded to the nearest tenth: 1.3 mL. Note: The corrected total daily dose is 300 mg x 3 = 900 mg/day, which falls within the safe range of 625 to 1,250 mg/day. Choice A (0.8 mL) results from incorrectly dividing 225 by 300. Choice C (1.5 mL) results from rounding 1.333 up rather than down. Choice D (3.0 mL) results from incorrectly multiplying rather than dividing.

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