NAPLEX Quiz: Compounding Ingredient Quantities

What this quiz covers

This quiz focuses on Compounding Ingredient Quantities, giving you a quick way to practice the rules, question types, and explanations that matter most for NAPLEX.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. 1.19 g
2. 11.92 g
3. 23.84 g (correct answer)
4. 0.119 g

Explanation: This question tests calculation involving milliequivalents (mEq) and unit conversions for electrolyte solutions. First, determine total mEq needed: (10 mEq/15 mL) × 480 mL = 320 mEq. Then convert to mass using the given conversion factor: 320 mEq × 74.5 mg/mEq = 23,840 mg = 23.84 g. The correct answer C (23.84 g) accurately represents this calculation. Option A (1.19 g) appears to calculate for 16 mEq instead of 320, option B (11.92 g) uses half the required amount, and option D (0.119 g) divides by 200. When working with mEq calculations, first determine total mEq needed, then use the substance-specific conversion factor. Always verify unit conversions and decimal placement in multi-step calculations.

Question 2

1. 0.1 g
2. 1 g (correct answer)
3. 10 g
4. 5 g

Explanation: This question assesses calculation of API for a low-concentration weight/weight (w/w) topical preparation. For 0.5% w/w in 200 g total: (0.5 g/100 g) × 200 g = 1 g. The correct answer B (1 g) represents this accurate calculation. Option A (0.1 g) divides by 10 suggesting 0.05% strength, option C (10 g) multiplies by 10 indicating 5% strength, and option D (5 g) suggests 2.5% strength. When working with fractional percentages, convert to decimal form (0.5% = 0.005) and multiply by total weight, or use the proportion method. Always double-check calculations for low-percentage preparations as small errors can significantly impact therapeutic effect.

Question 3

1. 90 mg
2. 900 mg (correct answer)
3. 9,000 mg
4. 450 mg

Explanation: This question assesses suspension totals. The key factor is 10 mg/mL × 90 mL = 900 mg of fluconazole. The correct answer, 900 mg, fits amber bottle. Choice A (90 mg) under by 10; choice C (9,000 mg) over by 10; choice D (450 mg) halves. Total mg = concentration × volume. Amber protects from light.

Question 4

1. 0.15 g
2. 1.5 g (correct answer)
3. 15 g
4. 0.5 g

Explanation: This question tests w/v for mouthwashes. The key factor is 0.5% w/v for 300 mL: (0.5/100) × 300 = 1.5 g of diphenhydramine HCl. The correct answer, 1.5 g, is sugar-free. Choice A (0.15 g) under by 10; choice C (15 g) over by 10; choice D (0.5 g) ignores volume. Grams = (percentage/100) × mL. Sugar-free aids diabetics.

Question 5

1. 0.9 g
2. 9 g (correct answer)
3. 90 g
4. 18 g

Explanation: This question assesses total active ingredient needs for oral suspensions from capsule contents. The key calculation is 50 mg/mL × 180 mL = 9,000 mg = 9 g of gabapentin. The correct answer, 9 g, accounts for the full batch volume accurately. Choice A (0.9 g) underestimates by a factor of 10; choice C (90 g) overestimates similarly; choice D (18 g) doubles the amount. Formula: concentration in mg/mL × volume in mL = total mg, then convert to grams if needed. Refrigerated storage enhances suspension stability.

Question 6

1. 3.75 g
2. 7.5 g (correct answer)
3. 0.75 g
4. 15 g

Explanation: This question evaluates the calculation of API quantity for a weight/volume (mg/mL) oral suspension preparation. The calculation requires converting the desired concentration to total drug amount: 50 mg/mL × 150 mL = 7,500 mg = 7.5 g. The correct answer B (7.5 g) represents this accurate calculation. Option A (3.75 g) incorrectly uses half the volume (75 mL), option C (0.75 g) appears to be a decimal error dividing by 10, and option D (15 g) doubles the correct amount suggesting 100 mg/mL concentration. When preparing suspensions with specific mg/mL concentrations, multiply the concentration by the total volume and convert units appropriately. Always double-check unit conversions between mg and g (1 g = 1,000 mg) to avoid medication errors.

Question 7

1. 2.025 g
2. 20.25 g (correct answer)
3. 202.5 g
4. 0.2025 g

Explanation: This question tests batch calculation for solid dosage form compounding, specifically capsules with a non-standard strength. The calculation involves multiplying the per-capsule dose by the total number of capsules: 225 mg × 90 capsules = 20,250 mg = 20.25 g. The correct answer B (20.25 g) accurately reflects this calculation. Option A (2.025 g) represents a decimal placement error (divided by 10), option C (202.5 g) multiplies by 10 suggesting a unit conversion error, and option D (0.2025 g) divides by 100. When compounding batches of capsules, calculate the total API needed by multiplying individual dose by quantity, then convert to appropriate weighing units. Always verify decimal placement when converting between mg and g to ensure accurate compounding.

Question 8

1. 30 mg
2. 300 mg (correct answer)
3. 3,000 mg
4. 75 mg

Explanation: This question assesses pediatric suspension calculations. The key factor is 4 mg/mL × 75 mL = 300 mg of propranolol HCl. The correct answer, 300 mg, matches the vehicle QS. Choice A (30 mg) under by 10; choice C (3,000 mg) over by 10; choice D (75 mg) quarters. Total mg = concentration × mL. Accurate measuring prevents dosing errors.

Question 9

1. 0.045 g
2. 0.45 g (correct answer)
3. 4.5 g
4. 45 g

Explanation: This question tests w/w concentration for topical creams. The key factor is 1% w/w of 45 g: (1/100) × 45 g = 0.45 g of clindamycin phosphate. The correct answer, 0.45 g, ensures precise formulation in the oil-in-water base. Choice A (0.045 g) is too low by a factor of 10; choice C (4.5 g) too high by 10; choice D (45 g) assumes 100%. Use: (percentage/100) × total weight = grams active. Uniform mixing is key for topical efficacy.

Question 10

1. 30 mg
2. 300 mg (correct answer)
3. 3,000 mg
4. 75 mg

Explanation: This question tests suspension calculations from tablets. The key factor is 2 mg/mL × 150 mL = 300 mg of amitriptyline. The correct answer, 300 mg, accounts for the full volume. Choice A (30 mg) under by 10; choice C (3,000 mg) over by 10; choice D (75 mg) quarters it. Formula: total mg = concentration × volume. Flavored vehicles mask taste for pediatrics.

Question 11

1. 0.3375 mg
2. 3.375 mg (correct answer)
3. 33.75 mg
4. 337.5 mg

Explanation: This question evaluates the total active ingredient calculation for compounded capsules with a specific dose per unit and batch quantity. The key calculation is 37.5 mcg/capsule × 90 capsules = 3,375 mcg, then 3,375 mcg ÷ 1,000 = 3.375 mg of levothyroxine. The correct answer, 3.375 mg, precisely accounts for the batch size without overage, maintaining dose accuracy. Choice A (0.3375 mg) underestimates by a factor of 10, likely a decimal error; choice C (33.75 mg) overestimates similarly; choice D (337.5 mg) multiplies by an extra factor of 10. A useful tip is to convert all units to milligrams early: total = (dose in mg) × quantity, where 37.5 mcg = 0.0375 mg, so 0.0375 × 90 = 3.375 mg. In capsule compounding, uniform filling prevents dose variability.

Question 12

1. 0.1 g
2. 1 g (correct answer)
3. 10 g
4. 100 g

Explanation: This question assesses capsule batch totals with fillers. The key calculation is 10 mg/capsule × 100 = 1,000 mg = 1 g of omeprazole. The correct answer, 1 g, uses lactose-free filler. Choice A (0.1 g) under by 10; choice C (10 g) over by 10; choice D (100 g) by 100. Total = dose × quantity. Allergen-free fillers prevent reactions.

Question 13

1. 0.4 g
2. 2 g
3. 4 g (correct answer)
4. 20 g

Explanation: This question examines w/v calculations for oral rinses. The key factor is 2% w/v for 200 mL: (2/100) × 200 = 4 g of lidocaine HCl. The correct answer, 4 g, provides the alcohol-free solution accurately. Choice A (0.4 g) undercalculates by 10; choice B (2 g) halves the volume; choice D (20 g) overestimates by 5. Formula: grams = (percentage/100) × volume in mL. Alcohol-free bases improve patient tolerance.

Question 14

1. 0.25 g
2. 2.5 g (correct answer)
3. 25 g
4. 250 g

Explanation: This question evaluates concentration calculations for pediatric oral suspensions. The key calculation is 25 mg/mL × 100 mL = 2,500 mg = 2.5 g of metronidazole. The correct answer, 2.5 g, matches the direct computation for the flavored vehicle. Choice A (0.25 g) underestimates by 10; choice C (25 g) overestimates by 10; choice D (250 g) by 100. Formula: total active = concentration × volume. Note potential need for equivalent adjustments if using salts like benzoate.

Question 15

1. 0.09 g
2. 0.9 g (correct answer)
3. 9 g
4. 90 g

Explanation: This question evaluates capsule batch for unavailable doses. The key calculation is 7.5 mg/capsule × 120 = 900 mg = 0.9 g of baclofen. The correct answer, 0.9 g, ignores overage. Choice A (0.09 g) under by 10; choice C (9 g) over by 10; choice D (90 g) by 100. Total = dose × quantity. Machines ensure uniformity.

Question 16

1. 0.15 g
2. 1.5 g (correct answer)
3. 3.0 g
4. 15 g

Explanation: This question examines w/w percentage calculations for topical ointments with allergen considerations. The key calculation is 5% w/w of 30 g total: (5/100) × 30 g = 1.5 g of salicylic acid. The correct answer, 1.5 g, provides the exact amount for the peanut-free base, ensuring therapeutic concentration. Choice A (0.15 g) is a decimal error underestimation; choice C (3.0 g) doubles it incorrectly; choice D (15 g) treats it as 50% erroneously. Always apply: grams active = (percentage/100) × total weight. Selecting appropriate bases avoids sensitivities in compounding.

Question 17

1. 0.24 mg
2. 2.4 mg (correct answer)
3. 24 mg
4. 12 mg

Explanation: This question assesses the calculation of active ingredient quantity for an oral suspension based on concentration and total volume. The key factor is converting 20 mcg/mL to mg for the total 120 mL volume, requiring 20 mcg/mL × 120 mL = 2,400 mcg, then 2,400 mcg ÷ 1,000 = 2.4 mg. The correct answer, 2.4 mg, accurately reflects this conversion and multiplication, ensuring the pediatric dose is properly formulated. Choice A (0.24 mg) results from omitting the volume multiplication or incorrect unit conversion; choice C (24 mg) overestimates by a factor of 10, possibly confusing mcg with mg; choice D (12 mg) might halve the volume incorrectly. Always use the formula: concentration × total volume for total active amount, followed by unit conversion. Compounding suspensions requires careful trituration to ensure uniform distribution and stability.

Question 18

1. 0.6 g
2. 1.2 g (correct answer)
3. 12 g
4. 2.4 g

Explanation: This question tests the concept of weight-in-weight (w/w) concentration in pharmaceutical compounding for topical creams. The key calculation involves determining the amount of active ingredient needed for a 2% w/w ketoconazole cream in a total of 60 g. The correct answer, 1.2 g, is calculated using the formula: (percentage/100) × total weight = (2/100) × 60 g = 1.2 g, ensuring the desired concentration is achieved accurately. Choice A (0.6 g) underestimates by using half the percentage or miscalculating the proportion, while choice C (12 g) overestimates by treating it as 20% instead of 2%; choice D (2.4 g) likely doubles the correct amount erroneously. A transferable tip is to always confirm units: percentage w/w means grams of solute per 100 grams of total mixture. In compounding, precise weighing on an electronic balance is crucial to maintain therapeutic efficacy and patient safety.

Question 19

1. 0.675 g (correct answer)
2. 6.75 g
3. 0.75 g
4. 67.5 g

Explanation: This question evaluates w/w for creams. The key calculation is 0.75% of 90 g: (0.75/100) × 90 = 0.675 g of metronidazole. The correct answer, 0.675 g, is fragrance-free. Choice B (6.75 g) over by 10; choice C (0.75 g) ignores total; choice D (67.5 g) by 100. Active = (percentage/100) × total weight. Slabs promote homogeneity.

Question 20

1. 0.03 g
2. 0.3 g (correct answer)
3. 3 g
4. 0.25 g

Explanation: This question evaluates suppository batch calculations. The key calculation is 25 mg/suppository × 12 = 300 mg = 0.3 g of hydrocortisone. The correct answer, 0.3 g, ignores overage as specified. Choice A (0.03 g) under by 10; choice C (3 g) over by 10; choice D (0.25 g) miscalculates dose. Total = dose × quantity, convert units. Molds ensure uniform suppositories.