Common Registration Assessment, Part 1

Dose information from packaging and labels

Some questions hand you a photo of a pack or a chart and expect you to find the numbers yourself. Three original questions that train that habit.

Published 5 October 2026. Independent revision material, not GPhC questions, not for patient care.

A pharmacist in a white coat reading the label on a medicine bottle from a shelf
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The Pharmaceutical Journal's article on using a resource or artefact says to get used to how dose information appears on outer packs, inner labels, prescriptions and administration charts. It also warns not to confuse how many times a day a dose is given with what counts as one dose.

Most of these questions combine a time window, an interval and a units trap. Draw the timeline, count the doses, then convert units once at the end.

The method

  1. Pull every number from the pack or chart into a short list with its unit.
  2. Work out how many doses fit the time window, including any first dose.
  3. Multiply by the amount per dose and the number of days.
  4. Convert micrograms, microlitres and percentages to the unit the question asks for.

Three practice questions

Work each one on paper first, then open the answer. All drugs and patients are fictional.

Question 1

A 0.1% w/v oro-mucosal spray gives 150 microlitres a spray. The maximum dose is 3 sprays every 2 hours, with a first dose at 08:00 and the last no later than 20:00. A patient uses it at this maximum for 5 days. How many mg of drug are used in total?

Show the answer

Answer: 15.75 mg

Working: Doses at 08:00, 10:00, 12:00, 14:00, 16:00, 18:00 and 20:00 is 7 times a day. Sprays = 3 × 7 × 5 = 105. Volume = 105 × 150 microlitres = 15.75 mL. 0.1% w/v is 1 mg/mL, so the drug used is 15.75 mg.

Question 2

Doses are taken every 4 hours between 07:00 and 22:00, starting with a first dose at 07:00. Each dose is 2 puffs of 100 micrograms. How many mg are inhaled over 3 days?

Show the answer

Answer: 2.4 mg

Working: The window is 15 hours. 15 ÷ 4 = 3.75, rounded down to 3 because a dose cannot be given before the full interval has passed, plus the starting dose, so 4 doses a day. 4 × 2 puffs × 3 days = 24 puffs. 24 × 100 micrograms = 2,400 micrograms = 2.4 mg.

Question 3

The label says 2 puffs twice daily and each inhaler holds 200 puffs. How many inhalers are needed for 90 days?

Show the answer

Answer: 2 inhalers

Working: 2 × 2 = 4 puffs a day. 4 × 90 = 360 puffs. 360 ÷ 200 = 1.8, so round up to 2 inhalers.

The journal's worked example

In the article's example a seven-year-old needs a benzydamine spray at the maximum dose for seven days between 08:00 and 21:00. The answer rounds the dosing intervals down to a whole number, adds a stat dose, converts 180 microlitres per spray and uses 0.15% w/v as 150 mg in 100 mL. The questions on this page use different drugs and numbers.

Where marks are lost

  • Rounding the number of doses up to the next interval when the full interval has not passed.
  • Forgetting the starting dose in a window.
  • Treating 0.1% w/v as 0.1 mg/mL; it is 1 mg/mL.

Frequently asked questions

Why round the number of intervals down?

A dose can only be given once a full interval has passed, so a part interval gives no extra dose. The starting dose is counted separately.

What does 0.15% w/v mean?

0.15 g in 100 mL, which is 150 mg in 100 mL or 1.5 mg/mL.

Sources

The questions above are original and use fictional drugs. PreRegExamPrep is not affiliated with or endorsed by the General Pharmaceutical Council.

Practise until the method is automatic

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More calculation topics

See also the formula sheet, the eight sample questions and the approved calculator page.