Common Registration Assessment, Part 1

Terbinafine tablet doses and course weeks by infection 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.

Person applying cream to their foot in a bathroom
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The NHS states that the usual terbinafine tablet dose is 1 tablet taken once a day, and the BNF lists the tablet dose as 250 mg once daily.

The NHS lists course lengths by infection: 2 to 4 weeks for jock itch, 2 to 6 weeks for athlete's foot, 4 weeks for ringworm, and 6 weeks to 3 months (sometimes longer) for a fungal nail infection.

The NHS lists creams, gels and sprays used once or twice a day for 1 to 2 weeks, and a single-use solution that is applied only once.

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 form, strength and course length stated in the question.
  2. Convert course weeks into days by multiplying by 7 before counting doses.
  3. Calculate one day first, then scale to the stated period.
  4. Count 1 tablet per day for a once-daily schedule; only round when the question says to.
  5. Keep milligrams, tablets and applications 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 terbinafine 250 mg once a day for 4 weeks for ringworm. How many milligrams is the full course?

Show the answer

Answer: 7,000 mg

Working: 4 weeks x 7 days = 28 days; 250 mg x 28 days = 7,000 mg.

Question 2

A fictional prescription reads terbinafine 250 mg once a day for 6 weeks for athlete's foot. How many tablets should be supplied?

Show the answer

Answer: 42 tablets

Working: 6 weeks x 7 days = 42 days; 1 tablet x 42 days = 42 tablets.

Question 3

A fictional patient uses terbinafine cream twice a day for 2 weeks. How many applications is the full course?

Show the answer

Answer: 28 applications

Working: 2 weeks x 7 days = 14 days; 2 applications x 14 days = 28 applications.

NHS: How and when to take or use terbinafine

https://www.nhs.uk/medicines/terbinafine/how-and-when-to-take-or-use-terbinafine/

Where marks are lost

  • Treating a course length in weeks as a count of days without multiplying by 7.
  • Reporting milligrams when the question asks for a tablet count or a count of applications.
  • 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 course-length calculation justify changing a real course?

No. Follow the course in the exercise. Real treatment length depends on the infection and 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.