Common Registration Assessment, Part 1
Tadalafil daily and on-demand tablet doses for the GPhC assessment
Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.
Published 31 October 2026. Independent revision material, not GPhC questions, not for patient care.
The NHS states that some people take 1 tablet 30 minutes before sex, that no more than 1 tablet is taken in a day, and that the effects can last up to 36 hours.
The NHS states that other people usually take 1 tablet at the same time every day, swallowed whole with water, and the BNF lists the once-daily dose as 5 mg, reduced to 2.5 mg once daily, adjusted according to response.
The BNF lists the on-demand starting dose as 10 mg taken at least 30 minutes before sexual activity, up to a maximum of 20 mg per dose.
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
- Check whether the question uses a daily schedule or an on-demand schedule before counting.
- Count at most 1 tablet in any day for either schedule.
- Multiply the daily tablet count by the number of days for a daily-schedule supply.
- Count tablets per stated occasion for an on-demand schedule, then scale.
- Keep milligrams and tablets separate; convert only if the question asks.
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 tadalafil 5 mg once a day. How many tablets are needed for 28 days?
Show the answer
Answer: 28 tablets
Working: 1 tablet x 28 days = 28 tablets.
Question 2
A fictional patient takes 1 on-demand tablet on 8 separate days in a 30-day month. How many tablets is that, and does it stay within the 1-tablet-a-day maximum?
Show the answer
Answer: 8 tablets; yes, no day has more than 1 tablet
Working: 8 days x 1 tablet = 8 tablets; 1 tablet per day is the stated maximum.
Question 3
A fictional prescription reads tadalafil 2.5 mg once a day for 90 days, supplied as 2.5 mg tablets. How many milligrams is the full course?
Show the answer
Answer: 225 mg
Working: 2.5 mg x 90 days = 225 mg.
NHS: Tadalafil
https://www.nhs.uk/medicines/tadalafil/
Where marks are lost
- Counting more than 1 tablet in a day on either schedule.
- Mixing the daily schedule and the on-demand schedule in the same count.
- 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 supply calculation justify changing between daily and on-demand dosing?
No. Follow the schedule in the exercise. Real dose choices 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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