Common Registration Assessment, Part 1

Lamotrigine 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 23 October 2026. Independent revision material, not GPhC questions, not for patient care.

Photograph of a glass near white tablets
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The BNF lists lamotrigine tablets in four strengths: 25 mg, 50 mg, 100 mg and 200 mg.

The BNF gives the usual adult start for epilepsy on its own as 25 mg once a day for 14 days, then 50 mg once a day for a further 14 days, then increased in steps of up to 100 mg every 7 to 14 days to a usual maintenance of 100 mg to 200 mg a day in 1 to 2 divided doses.

Each question fixes the values needed for its arithmetic. Write the unit beside every step and keep each titration step separate from a running total. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Identify the exact strength, dose and step length supplied in the question.
  2. Calculate one dose first; divide prescribed mg by mg per tablet.
  3. Scale to the stated step length only when a supply is requested.
  4. Keep each titration step at its own dose before adding totals.
  5. Check the tablet count is a whole number before reporting it.

Three practice questions

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

Question 1

A fictional plan starts lamotrigine at 25 mg once a day using 25 mg tablets for 14 days. How many tablets is this step?

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Answer: 14 tablets

Working: 25 ÷ 25 = 1 tablet a day. 1 × 14 = 14 tablets.

Question 2

A fictional plan continues lamotrigine at 50 mg once a day using 25 mg tablets for a further 14 days. How many tablets is this step?

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Answer: 28 tablets

Working: 50 ÷ 25 = 2 tablets a day. 2 × 14 = 28 tablets.

Question 3

A fictional plan maintains lamotrigine at 100 mg a day in 2 divided doses using 50 mg tablets for 28 days. How many tablets is the month?

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Answer: 56 tablets

Working: 100 ÷ 2 = 50 mg per dose, so 50 ÷ 50 = 1 tablet per dose. Two doses a day is 2 tablets a day. 2 × 28 = 56 tablets.

Exam approach

Step-by-step titrations are small sums in sequence. Do not total until every step is settled at its own dose.

Where marks are lost

  • Carrying the first step's dose across the whole titration.
  • Mixing up the four strengths when the strength is stated in the question.
  • Counting one dose a day when the question says 2 divided doses.

Frequently asked questions

Are these official assessment questions?

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

Do I need to memorise the titration schedule?

The exercise supplies the doses. In the assessment, read any given product information exactly as written.

How should I check the answer?

Work one step at a time, then add the step totals and check the count against the stated strengths.

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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More calculation topics

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