Common Registration Assessment, Part 1

Pyrazinamide weight-band tablets and course counts for the GPhC assessment

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

Published 13 November 2026. Independent revision material, not GPhC questions, not for patient care.

Pink and white capsules spilled from a clear bottle onto a flat surface
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 pyrazinamide 500 mg tablets gives weight bands for the standard unsupervised 2-month treatment: a maximum of 1.5 g daily under 50 kg body weight (three 500 mg tablets) and a maximum of 2.0 g daily over 50 kg body weight (four 500 mg tablets).

For intermittent supervised treatment, the same information gives 2.0 g three times a week under 50 kg (four tablets) and 2.5 g three times a week over 50 kg (five tablets).

For children, the product information gives 35 mg per kg of body weight per day for standard treatment, with stated gram equivalents for children aged 4 to 10 and 11 to 14.

Each question fixes the values needed for its arithmetic. Keep the daily and three-times-weekly schedules separate and state the schedule beside every answer. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Check whether the question uses the daily schedule or the three-times-weekly supervised schedule.
  2. Read off the weight band: under 50 kg, or over 50 kg.
  3. Convert the gram figure to 500 mg tablets by multiplying by two.
  4. For children, multiply the body weight in kg by 35 mg.
  5. For course counts, count doses in the course first, then multiply by tablets per dose.

Three practice questions

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

Question 1

A fictional adult weighs 45 kg and is prescribed pyrazinamide on the standard daily schedule. What is the maximum daily dose in the printed weight band, and how many 500 mg tablets is that?

Show the answer

Answer: 1.5 g daily; three 500 mg tablets

Working: Under 50 kg the printed maximum is 1.5 g. 1.5 g = 1,500 mg, and 1,500 / 500 = 3 tablets.

Question 2

A fictional adult weighs 70 kg and is prescribed pyrazinamide three times a week under the intermittent supervised schedule. How many 500 mg tablets are taken at each dose, and how many tablets does an 8-week course need?

Show the answer

Answer: Five tablets per dose; 120 tablets for the course

Working: Over 50 kg the intermittent dose is 2.5 g, which is 2,500 / 500 = 5 tablets. Three doses a week for 8 weeks gives 3 x 8 = 24 doses, and 24 x 5 = 120 tablets.

Question 3

Two fictional adults weigh 49 kg and 51 kg, both on the standard daily schedule. What maximum daily dose does the printed table give each, and how many 500 mg tablets is each?

Show the answer

Answer: 1.5 g (three tablets) for the 49 kg adult; 2.0 g (four tablets) for the 51 kg adult

Working: Under 50 kg gives 1.5 g, so the 49 kg adult takes 1,500 / 500 = 3 tablets. Over 50 kg the maximum is 2.0 g, so the 51 kg adult takes 2,000 / 500 = 4 tablets.

eMC SmPC: Pyrazinamide 500 mg Tablets

https://www.medicines.org.uk/emc/product/101051/smpc

Where marks are lost

  • Applying the daily-schedule weight band to a three-times-weekly supervised dose.
  • Reading the wrong side of the 50 kg boundary.
  • Counting days instead of doses when totalling a three-times-weekly course.

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?

Pick the schedule (daily or three times weekly), read the weight band, then convert grams to 500 mg tablets by multiplying by two.

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.