Common Registration Assessment, Part 1

Dihydrocodeine modified-release tablets and twelve hourly doses for the GPhC assessment

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

Published 1 November 2026. Independent revision material, not GPhC questions, not for patient care.

Yellow tablets arranged on a pharmacy counting tray
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The NHS describes dihydrocodeine as a medicine used for pain.

The manufacturer's UK product information lists modified-release tablets of 60 mg, 90 mg and 120 mg taken every 12 hours.

An every 12 hours schedule means 2 doses a day, so the daily total is double the single dose.

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 strength and the stated dosing interval.
  2. Divide 24 hours by the stated interval to count daily doses.
  3. Calculate one day first, then scale to the stated number of days or weeks.
  4. Convert weeks into days by multiplying by 7 before counting doses.
  5. Keep milligrams and tablet counts separate; convert only if 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 dihydrocodeine modified-release 60 mg every 12 hours. How many milligrams is that each day and each week?

Show the answer

Answer: 120 mg each day; 840 mg each week

Working: 60 mg x 2 doses = 120 mg a day; 120 mg x 7 days = 840 mg.

Question 2

A fictional prescription reads dihydrocodeine modified-release 90 mg every 12 hours. How many tablets should be supplied for 14 days?

Show the answer

Answer: 28 tablets

Working: 24 hours / 12 hours = 2 doses a day; 2 tablets x 14 days = 28 tablets.

Question 3

A fictional patient's dose rises from 60 mg every 12 hours to 90 mg every 12 hours. How many extra milligrams is that each day and across a week?

Show the answer

Answer: 60 mg extra each day; 420 mg extra across a week

Working: (90 mg - 60 mg) x 2 doses = 60 mg extra a day; 60 mg x 7 days = 420 mg.

NHS: Dihydrocodeine

https://www.nhs.uk/medicines/dihydrocodeine/

Where marks are lost

  • Counting one dose a day for an every 12 hours schedule instead of two.
  • Comparing single doses when the question asks about daily totals.
  • 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.

Does modified-release change the arithmetic?

Only the schedule matters for counting: every 12 hours means 2 doses a day. The release mechanism does not change the maths.

How should I check the answer?

Check the requested unit, then work backwards from the quantity to the stated dose, interval 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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See also the formula sheet, the eight sample questions and the approved calculator page.