Common Registration Assessment, Part 1

Famotidine 20 mg and 40 mg doses and ulcer course weeks for the GPhC assessment

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

Published 14 November 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 manufacturer's UK product information for famotidine gives 40 mg at night for duodenal ulcer. Healing occurs in most patients within 4 weeks, and where the ulcer has not healed in that period, treatment continues for a further 4 weeks. To prevent relapse of duodenal ulceration, the recommended dose is 20 mg at night.

For benign gastric ulcer the same information gives 40 mg at night for 4 to 8 weeks. For Zollinger-Ellison syndrome, patients not already on antisecretory therapy start on 20 mg every 6 hours, adjusted to individual response, and doses up to 800 mg daily have been used.

Because famotidine is eliminated mainly through the kidneys, the product information reduces the daily dose by 50% when creatinine clearance is less than 30 ml/min.

Each question fixes the values needed for its arithmetic. Match the indication to its dose and course length before calculating. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Give 40 mg at night for duodenal ulcer and 20 mg at night for relapse prevention.
  2. Allow 4 weeks for healing and continue a further 4 weeks where the ulcer has not healed.
  3. For benign gastric ulcer, give 40 mg at night for 4 to 8 weeks.
  4. For Zollinger-Ellison syndrome, start at 20 mg every 6 hours and count the daily total.
  5. Halve the daily dose when creatinine clearance is less than 30 ml/min.

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 40 mg at night for a duodenal ulcer and needs the further 4 weeks because the ulcer has not healed. How many 40 mg tablets is the full 8-week course?

Show the answer

Answer: 56 tablets

Working: 1 tablet a night x 7 nights = 7 tablets a week. 7 x 8 weeks = 56 tablets.

Question 2

A fictional patient with Zollinger-Ellison syndrome takes 20 mg every 6 hours. What is the daily total?

Show the answer

Answer: 80 mg a day

Working: 24 hours / 6 hours = 4 doses a day. 4 x 20 mg = 80 mg a day.

Question 3

A fictional patient with a creatinine clearance of 25 ml/min is prescribed 40 mg at night for a duodenal ulcer. What daily dose does the product information give?

Show the answer

Answer: 20 mg a day

Working: The product information reduces the daily dose by 50% when creatinine clearance is less than 30 ml/min. 40 mg x 0.5 = 20 mg a day.

eMC SmPC: Famotidine 20 mg Film-coated Tablets

https://www.medicines.org.uk/emc/product/15972/smpc

Where marks are lost

  • Swapping the 40 mg treatment dose and the 20 mg relapse prevention dose.
  • Stopping a duodenal ulcer course at 4 weeks when the ulcer has not healed, instead of continuing for a further 4 weeks.
  • Reading 20 mg every 6 hours as a daytime-only regimen and totalling fewer than 4 doses.

Frequently asked questions

Are these official assessment questions?

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

Does this calculation decide a real dose?

No. Follow the stated prescription in the exercise. Real dosing follows the prescriber and the product information for the named product.

How should I check the answer?

Match the indication to its dose and course length, multiply a 6-hourly regimen by four for the daily total, and halve the daily dose when creatinine clearance is less than 30 ml/min.

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.