Common Registration Assessment, Part 1

Lisdexamfetamine capsule strengths and morning doses for the GPhC assessment

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

Published 2 November 2026. Independent revision material, not GPhC questions, not for patient care.

Morning coffee and breakfast beside a sunlit window
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The cited UK product information is for Elvanse 30 mg hard capsules, containing lisdexamfetamine dimesylate, taken once a day in the morning. Each exercise states the strength needed for its calculation.

That product information recommends a starting dose of 30 mg once a day in the morning, increased in 10 mg or 20 mg steps at about weekly intervals.

The same information sets a maximum recommended dose of 70 mg 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 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 frequency stated in the question.
  2. Count one capsule per day for each capsule taken once a day in the morning before scaling to the stated period.
  3. Calculate one week first during a stated titration, then add the weeks.
  4. Compare the daily total against the stated 70 mg maximum only when the question asks.
  5. Keep milligrams and capsules 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 lisdexamfetamine 30 mg once a day in the morning. How many capsules and how many milligrams is a 28-day supply?

Show the answer

Answer: 28 capsules; 840 mg

Working: 1 capsule x 28 days = 28 capsules; 30 mg x 28 days = 840 mg.

Question 2

A fictional patient takes 30 mg once a day for 1 week, then 50 mg once a day for the next 3 weeks. How many milligrams is the full 4 weeks?

Show the answer

Answer: 1,260 mg

Working: (30 mg x 7 days) + (50 mg x 21 days) = 210 mg + 1,050 mg = 1,260 mg.

Question 3

A fictional patient is taking 70 mg each morning and asks to add a 20 mg capsule the same day. Is the combined daily amount within the stated maximum?

Show the answer

Answer: No; 90 mg is above the stated 70 mg daily maximum

Working: 70 mg + 20 mg = 90 mg; 90 mg is more than the stated 70 mg maximum recommended dose.

eMC SmPC: Elvanse 30 mg hard capsules

https://www.medicines.org.uk/emc/product/14089/smpc

Where marks are lost

  • Counting a once daily morning dose more than once in a day.
  • Adding a titration step without recalculating the daily total.
  • 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 dose-total calculation justify changing a real dose?

No. Follow the steps in the exercise. Real dose changes are gradual and 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.

Practise until the method is automatic

Try 15 free questions with worked answers. No sign-up required.

Try 15 free questionsSee pricing

More calculation topics

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