Common Registration Assessment, Part 1

GTN spray and tablet doses during angina attacks for the GPhC assessment

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

Published 29 October 2026. Independent revision material, not GPhC questions, not for patient care.

Woman using a medicine mouth spray
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The NHS states that 1 dose of glyceryl trinitrate (GTN) is either 1 tablet under the tongue or 1 to 2 sprays under the tongue, and that no more than 2 doses should be used during an angina attack, with a second dose only if still in pain after 5 minutes.

The NHS lists the usual rectal ointment dose as approximately 375 mg applied twice a day, and advises not to use tablets from a bottle first opened more than 8 weeks ago.

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, dose count and frequency supplied in the question.
  2. Treat 1 dose as 1 tablet or 1 to 2 sprays exactly as the question states.
  3. Calculate one dose first, then scale to the stated frequency and duration.
  4. Convert mg to g by dividing by 1,000 only when the answer is requested in grams.
  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 patient uses 1 spray under the tongue for chest pain and, still in pain after 5 minutes, uses 1 more spray. How many doses and how many sprays is that in total?

Show the answer

Answer: 2 doses (2 sprays)

Working: 1 dose = 1 to 2 sprays here 1 spray; 1 + 1 = 2 sprays, which is the stated maximum of 2 doses in an attack.

Question 2

A fictional prescription specifies GTN rectal ointment 375 mg applied twice a day for 7 days. How many mg is the total course, and what is that in grams?

Show the answer

Answer: 5,250 mg (5.25 g)

Working: 375 mg × 2 = 750 mg per day; 750 × 7 days = 5,250 mg; 5,250 ÷ 1,000 = 5.25 g.

Question 3

A fictional bottle of GTN tablets is first opened on 1 June. The label says do not use tablets from a bottle opened more than 8 weeks ago. On what date do the tablets reach 8 weeks after opening?

Show the answer

Answer: 27 July

Working: 8 weeks = 56 days; 1 June + 56 days = 27 July (29 days left in June after 1 June, then 27 days into July).

NHS: How and when to take glyceryl trinitrate (GTN)

https://www.nhs.uk/medicines/glyceryl-trinitrate-gtn/how-and-when-to-take-glyceryl-trinitrate-gtn/

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.

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More calculation topics

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