Common Registration Assessment, Part 1

Sumatriptan tablet strengths and repeat-dose maximums for the GPhC assessment

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

Published 22 October 2026. Independent revision material, not GPhC questions, not for patient care.

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Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The BNF lists sumatriptan tablets in two strengths: 50 mg and 100 mg.

The BNF gives the adult dose for migraine as 50 mg to 100 mg for one dose at the start of an attack; a dose can be repeated after at least 2 hours only if the migraine comes back, up to a maximum of 300 mg a day.

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

The method

  1. Identify the exact strength, dose and timing supplied in the question.
  2. Check any repeat dose is at least 2 hours after the previous one.
  3. Add up the day total in mg before comparing it with the stated maximum.
  4. Divide by the tablet strength only after the mg totals are settled.
  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 specifies sumatriptan 50 mg at the start of a migraine, with one repeat 50 mg dose 3 hours later when the migraine returned. How many 50 mg tablets were taken, and what was the total dose?

Show the answer

Answer: 2 tablets, 100 mg in total

Working: One 50 mg dose, then one 50 mg repeat after 3 hours. The gap is more than 2 hours, so the repeat fits the plan. 2 × 50 = 100 mg.

Question 2

A fictional patient took sumatriptan 100 mg at 8 am, 100 mg at 11 am and 100 mg at 3 pm. They ask about a fourth 100 mg dose at 6 pm. Using the stated 300 mg daily maximum, is the fourth dose within it?

Show the answer

Answer: No. 300 mg is already taken, so a fourth 100 mg dose would exceed the maximum

Working: 100 + 100 + 100 = 300 mg taken. The maximum is 300 mg a day, so no further dose fits. 300 + 100 = 400 mg would be 100 mg over.

Question 3

A fictional prescription supplies sumatriptan 50 mg tablets with directions to take one dose at the start of an attack, repeating once after at least 2 hours if the migraine returns. How many tablets could one attack use at most?

Show the answer

Answer: 2 tablets

Working: One initial 50 mg dose plus one permitted 50 mg repeat is 2 tablets. The stated plan allows a single repeat only.

Exam approach

Maximum-dose questions are really two sums: work the dose, then test it against the cap. Show both before answering.

Where marks are lost

  • Treating the repeat dose as allowed immediately instead of after at least 2 hours.
  • Adding doses without checking the running day total against the stated maximum.
  • Mixing up the 50 mg and 100 mg strengths when the strength is stated in the question.

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 maximum?

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

How should I check the answer?

Add the doses in mg first, then test the total against the stated daily maximum before reporting tablets.

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.