Common Registration Assessment, Part 1

Oxycodone immediate and modified-release 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.

Black and white photograph of tablets resting on a bottle cap
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The NHS describes oxycodone as a medicine used for severe pain.

The manufacturer's UK product information for OxyNorm lists immediate-release capsules of 5 mg, 10 mg and 20 mg taken every 4 to 6 hours, with a usual starting dose of 5 mg.

The product information for OxyContin lists modified-release tablets taken every 12 hours with a usual starting dose of 10 mg, and states that 10 mg of oral oxycodone is equivalent to about 20 mg of oral morphine.

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 whether the stated product is immediate-release or modified-release before counting doses.
  2. Divide 24 hours by the stated dose interval to count daily doses.
  3. Calculate one day first, then scale to the stated number of days.
  4. Apply a stated equivalence factor only when the question asks for an equivalent amount.
  5. Keep milligrams and capsule or 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 oxycodone immediate-release 5 mg capsules every 6 hours. How many milligrams is that each day, and how many capsules is a 7-day supply?

Show the answer

Answer: 20 mg each day; 28 capsules

Working: 24 hours / 6 hours = 4 doses a day; 5 mg x 4 doses = 20 mg; 4 capsules x 7 days = 28 capsules.

Question 2

A fictional patient takes oxycodone modified-release 10 mg every 12 hours. Using the stated equivalence, how many milligrams of oral morphine a day is this equivalent to?

Show the answer

Answer: 40 mg

Working: 10 mg x 2 doses = 20 mg of oxycodone a day; 20 mg x 2 = 40 mg of oral morphine.

Question 3

A fictional patient may take oxycodone immediate-release 5 mg capsules every 4 hours at most. What is the maximum daily amount, and the maximum number of capsules over 3 days?

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Answer: 30 mg a day; 18 capsules

Working: 24 hours / 4 hours = 6 doses a day; 5 mg x 6 doses = 30 mg; 6 capsules x 3 days = 18 capsules.

NHS: Oxycodone

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

Where marks are lost

  • Mixing up the 4 to 6 hourly immediate-release schedule with the 12-hourly modified-release schedule.
  • Applying an equivalence factor when the question asks only for the stated medicine's amount.
  • 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 an equivalence calculation justify switching a real patient's medicine?

No. Follow the steps in the exercise. Real opioid conversions need clinical judgement and specialist guidance.

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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