Common Registration Assessment, Part 1

Docusate 100 mg capsules and divided daily doses for the GPhC assessment

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

Published 4 November 2026. Independent revision material, not GPhC questions, not for patient care.

Amber capsules spilling from a glass container onto a white surface
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The manufacturer's UK product information for Dioctyl 100 mg capsules states that adults can take up to 500 mg daily in divided doses.

The same information states that treatment should be started with large doses, which are then decreased as the patient's condition improves.

The NHS notes that docusate comes as capsules or a liquid, and that adults and children aged 12 years and over can start with one capsule three times a day.

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 a supply period. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Identify the stated daily dose in milligrams and how many divided doses it is split into.
  2. Divide the daily dose by the capsule strength to count capsules per day.
  3. Multiply the daily capsule count by the stated number of days for a supply quantity.
  4. Keep milligrams and capsules separate; convert only when the question asks.

Three practice questions

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

Question 1

A fictional patient takes docusate 300 mg daily in three divided doses using 100 mg capsules. How many capsules are taken each day?

Show the answer

Answer: 3 capsules

Working: 300 mg / 100 mg per capsule = 3 capsules each day, one capsule per divided dose.

Question 2

A fictional patient takes the maximum docusate dose of 500 mg daily using 100 mg capsules. How many capsules is this each day?

Show the answer

Answer: 5 capsules

Working: 500 mg / 100 mg per capsule = 5 capsules each day.

Question 3

A fictional prescription reads docusate 400 mg daily in four divided doses using 100 mg capsules for seven days. How many capsules should be supplied?

Show the answer

Answer: 28 capsules

Working: 400 mg / 100 mg per capsule = 4 capsules each day. 4 capsules x 7 days = 28 capsules.

eMC SmPC: Dioctyl 100 mg capsules

https://www.medicines.org.uk/emc/product/6218/smpc

Where marks are lost

  • Using the up-to-500-mg daily figure when the question states a lower daily dose.
  • Answering with capsules per divided dose when the question asks for capsules per day or per course.
  • Forgetting that each capsule contains 100 mg.

Frequently asked questions

Are these official assessment questions?

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

Is the maximum always the amount supplied?

No. Calculate from the daily dose stated in the question. The maximum is a limit, not the automatic dose.

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.

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.