Common Registration Assessment, Part 1
Citalopram drops and tablet equivalents for the GPhC assessment
Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.
Published 17 October 2026. Independent revision material, not GPhC questions, not for patient care.
The NHS lists citalopram tablets in 10 mg, 20 mg and 40 mg strengths, and states that with the liquid drops, 4 drops is the same as a 10 mg tablet.
The usual adult dose is 20 mg a day, up to a maximum of 40 mg a day. For people over 65 or with liver problems, the maximum recommended dose is 20 mg a day.
Each question fixes the values needed for its arithmetic. Write the unit beside every step and keep drops and tablets as separate counts. All prescriptions and patients here are fictional; these are revision materials, not for patient care.
The method
- Identify whether the question works in drops or tablets and the stated equivalence.
- Convert a mg dose to drops using the stated ratio before calculating.
- For tablets divide prescribed mg by mg per tablet.
- Scale to the stated duration only when a total supply is requested.
- Check any dose against a stated maximum 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 prescription specifies citalopram 20 mg once a day using the liquid drops, where 4 drops equal a 10 mg tablet. How many drops is one dose?
Show the answer
Answer: 8 drops
Working: 10 mg needs 4 drops, so 20 mg needs 20 ÷ 10 × 4 = 8 drops.
Question 2
A fictional prescription specifies citalopram 40 mg once a day using 20 mg tablets. How many tablets are needed for 28 days?
Show the answer
Answer: 56 tablets
Working: 40 ÷ 20 = 2 tablets a day. 2 × 28 = 56 tablets.
Question 3
A fictional prescription specifies citalopram 30 mg once a day using the liquid drops, where 4 drops equal a 10 mg tablet. How many drops is one dose?
Show the answer
Answer: 12 drops
Working: 30 ÷ 10 × 4 = 12 drops.
Exam approach
Treat the stated equivalence as a ratio: 4 drops per 10 mg. Convert the dose first, then count. Drops and tablets never share a total.
Where marks are lost
- Applying the 4 drop equivalence per tablet instead of per 10 mg.
- Mixing drop counts and tablet counts in one answer.
- 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.
Why is the drop equivalence stated as per 10 mg?
Because the NHS gives the equivalence as 4 drops being the same as a 10 mg tablet; scale from that ratio.
How should I check the answer?
Check the requested unit, then work backwards from the quantity to the stated dose and duration.
Sources
- NHS: How and when to take citalopram
- GPhC, Common Registration Assessment specification and permitted items for 2026
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.