Common Registration Assessment, Part 1
Risperidone liquid volumes and titration steps for the GPhC assessment
Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.
Published 24 October 2026. Independent revision material, not GPhC questions, not for patient care.
The NHS lists risperidone liquid as 1 mg in 1 mL and tablets from 0.25 mg to 6 mg. The BNF psychosis schedule starts at 2 mg daily on day 1 and 4 mg daily on day 2.
In older adults the BNF titration starts at 500 micrograms twice daily, increased in 500 microgram steps.
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
- Identify the exact formulation, strength, dose and frequency supplied in the question.
- Convert an X mg/5 mL strength to mg/mL if a dose-to-volume conversion is needed.
- Calculate one dose first; for tablets or capsules divide prescribed mg by mg per unit.
- Scale to the stated frequency and duration only when a total quantity is requested.
- 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 day 1 dose is risperidone 2 mg, using the liquid containing 1 mg in 1 mL. What volume is one dose?
Show the answer
Answer: 2 mL
Working: 2 ÷ 1 × 1 = 2 mL.
Question 2
A fictional schedule is risperidone 2 mg on day 1 and 4 mg on day 2. What is the total over the two days?
Show the answer
Answer: 6 mg
Working: 2 + 4 = 6 mg, which is 6 mL of the liquid in total.
Question 3
A fictional older adult takes risperidone 500 micrograms twice daily, using the liquid containing 1 mg in 1 mL. What daily volume is that?
Show the answer
Answer: 1 mL
Working: 500 micrograms × 2 = 1,000 micrograms = 1 mg per day; 1 ÷ 1 × 1 = 1 mL.
NHS: How and when to take risperidone
https://www.nhs.uk/medicines/risperidone/how-and-when-to-take-risperidone/
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.
Practise until the method is automatic
Try 15 free questions with worked answers. No sign-up required.
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See also the formula sheet, the eight sample questions and the approved calculator page.