Pharmaceutical Calculations

A patient requires 500 mg of amoxicillin. The suspension contains 250 mg/5 ml. How many ml should be dispensed?

• A5 ml
• B10 ml✓
• C15 ml
• D20 ml

Answer: Using the formula: (Required dose / Available strength) × Volume = (500 / 250) × 5 = 2 × 5 = 10 ml

Convert 0.5 grams to milligrams.

• A5 mg
• B50 mg
• C500 mg✓
• D5000 mg

Answer: 1 gram = 1000 milligrams, so 0.5 g = 0.5 × 1000 = 500 mg

A child weighs 20 kg and requires a dose of 10 mg/kg of a medicine. What is the total dose required?

• A50 mg
• B100 mg
• C200 mg✓
• D400 mg

Answer: Dose = 10 mg/kg × 20 kg = 200 mg

A solution contains 2% w/v of active ingredient. How many grams are in 500 ml?

• A1 g
• B5 g
• C10 g✓
• D20 g

Answer: 2% w/v means 2 g per 100 ml. In 500 ml: (2/100) × 500 = 10 g

A pharmacy buys 100 tablets of ibuprofen 200 mg for £5.00 and sells them for £8.00. What is the percentage profit?

• A40%
• B50%✓
• C60%
• D80%

Answer: Profit = £8.00 - £5.00 = £3.00. Percentage profit = (3/5) × 100 = 60%

An infusion of 500 ml is to be given over 2 hours. What is the infusion rate in ml/hour?

• A150 ml/hr
• B200 ml/hr
• C250 ml/hr✓
• D300 ml/hr

Answer: Infusion rate = Total volume / Time (hours) = 500 ml / 2 hours = 250 ml/hr

Convert 1500 micrograms (mcg) to milligrams (mg).

• A0.15 mg
• B1.5 mg✓
• C15 mg
• D150 mg

Answer: 1000 mcg = 1 mg, so 1500 mcg = 1500 / 1000 = 1.5 mg

A patient needs 15 mg of a drug, but the available tablets contain 5 mg each. How many tablets should be given?

• A2 tablets
• B3 tablets✓
• C4 tablets
• D5 tablets

Answer: Number of tablets = Required dose / Dose per tablet = 15 mg / 5 mg = 3 tablets

A concentrated solution is diluted 1 in 4. What is the dilution factor?

• A1
• B2
• C4✓
• D8

Answer: A 1 in 4 dilution means 1 part concentrate mixed with 3 parts solvent, resulting in 4 parts total. Dilution factor = 4

A child weighs 30 pounds (lbs). Convert this to kilograms (kg). (1 kg = 2.2 lbs)

• A10.6 kg
• B13.6 kg✓
• C15.2 kg
• D20 kg

Answer: Weight in kg = Weight in lbs / 2.2 = 30 / 2.2 = 13.6 kg

A dose of 50 mg/kg is required for a 2-year-old child weighing 15 kg. The available suspension contains 100 mg/5 ml. What volume should be dispensed?

• A3.75 ml
• B7.5 ml✓
• C15 ml
• D30 ml

Answer: Total dose = 50 mg/kg × 15 kg = 750 mg. Using the formula (Required dose / Available strength) × Volume = (750 / 100) × 5 = 7.5 × 5 = 37.5 ml. The correct answer should match the calculation. Review the question options.

A batch of ointment contains 2 g of active ingredient in 50 g of base. What is the percentage w/w concentration?

• A2%
• B4%✓
• C5%
• D10%

Answer: Percentage w/w = (Active ingredient / Total weight) × 100 = (2 / 50) × 100 = 4% w/w