Common Registration Assessment, Part 1

Carbocisteine capsules, sachets and liquid doses for the GPhC assessment

Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.

Published 28 October 2026. Independent revision material, not GPhC questions, not for patient care.

Blue tablets spilling from an orange prescription bottle
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The NHS lists carbocisteine as 375 mg capsules (usual adult dose 2 capsules 3 times a day, reducing to 1 capsule 4 times a day when symptoms improve), a liquid or syrup containing 250 mg in 5 mL (15 mL 3 times a day, reducing to 10 mL), and sachets containing 750 mg in 10 mL (1 sachet 3 times a day).

Each presentation delivers 750 mg per dose at its usual starting dose, so switching between them is an arithmetic exercise in this context only.

Each question fixes the values needed for its arithmetic. Write the unit beside every step and distinguish a single dose from a daily total or course supply. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Identify the exact formulation, strength, dose and frequency supplied in the question.
  2. Convert an X mg/5 mL strength to mg/mL if a dose-to-volume conversion is needed.
  3. Calculate one dose first; for tablets or capsules divide prescribed mg by mg per unit.
  4. Scale to the stated frequency and duration only when a total quantity is requested.
  5. Apply whole-container or complete-day rounding only if the question specifies it.

Three practice questions

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

Question 1

A fictional prescription specifies carbocisteine 2 capsules of 375 mg three times a day for 7 days. How many capsules are needed?

Show the answer

Answer: 42 capsules

Working: 2 × 3 = 6 capsules per day; 6 × 7 days = 42 capsules.

Question 2

A fictional plan uses carbocisteine syrup 250 mg in 5 mL at 15 mL three times a day for 5 days. How many mL are needed in total?

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Answer: 225 mL

Working: 15 × 3 = 45 mL per day; 45 × 5 days = 225 mL.

Question 3

A fictional prescription specifies one 750 mg carbocisteine sachet twice a day after improvement, for 14 days. How many sachets, and how many mg per day?

Show the answer

Answer: 28 sachets (1,500 mg per day)

Working: 2 × 14 days = 28 sachets; 750 × 2 = 1,500 mg per day.

NHS: How and when to take carbocisteine

https://www.nhs.uk/medicines/carbocisteine/how-and-when-to-take-carbocisteine/

Where marks are lost

  • Using a remembered strength or schedule instead of the stated product.
  • Reporting a daily total when the question asks for one dose or the course.
  • Treating arithmetic as evidence that a real prescription is clinically suitable.

Frequently asked questions

Are these official assessment questions?

No. They are original revision exercises, not official GPhC questions and not for patient care.

Can a quantity calculation justify a formulation switch?

No. Follow the formulation and prescription in the exercise. Real switches and dose changes need clinical checks.

How should I check the answer?

Check the requested unit, then work backwards from the quantity to the stated dose and duration.

Sources

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

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More calculation topics

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