Common Registration Assessment, Part 1

Topiramate tablet strengths and titration steps for the GPhC assessment

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

Published 26 October 2026. Independent revision material, not GPhC questions, not for patient care.

Pink and blue pills on a white surface
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The NHS lists a low starting dose of 25 mg to 50 mg a day, increased over several weeks; the usual dose for epilepsy is 100 mg to 200 mg a day taken as 2 doses.

Because topiramate can harm an unborn baby and migraine has safer alternatives in pregnancy, the NHS says that if there is a chance someone could become pregnant while taking it, their doctor will enrol them on a pregnancy prevention programme.

The BNF migraine schedule starts at 25 mg once daily at night for 1 week, increased in weekly steps of 25 mg, to a usual 50 mg to 100 mg daily in 2 divided doses.

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 titration starts topiramate at 25 mg each night for 7 nights, using 25 mg tablets. How many tablets cover the first week?

Show the answer

Answer: 7 tablets

Working: 1 tablet × 7 nights = 7 tablets.

Question 2

A fictional plan is topiramate 100 mg a day for epilepsy, taken as 2 equal doses, using 50 mg tablets. How many tablets is one dose?

Show the answer

Answer: 1 tablet

Working: 100 ÷ 2 = 50 mg per dose; 50 ÷ 50 = 1 tablet.

Question 3

A fictional titration is topiramate 25 mg once at night in week 1, then 25 mg twice a day in week 2. What is the total amount over the 2 weeks?

Show the answer

Answer: 525 mg

Working: 25 × 7 = 175 mg; 25 × 2 × 7 = 350 mg; 175 + 350 = 525 mg.

NHS: How and when to take topiramate

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

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.

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.