Common Registration Assessment, Part 1

Imiquimod sachet applications and treatment weeks for the GPhC assessment

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

Published 10 November 2026. Independent revision material, not GPhC questions, not for patient care.

A woman applying cream to her arm
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The manufacturer's UK product information for Aldara 5% cream states that for external genital warts in adults the cream is applied 3 times per week (for example Monday, Wednesday and Friday) prior to normal sleeping hours, left on the skin for 6 to 10 hours, and continued until clearance or for a maximum of 16 weeks per episode of warts.

The same information states that for actinic keratosis the cream is applied 3 times per week for four weeks, left on for approximately 8 hours, with a maximum recommended dose of one sachet per application, and that for superficial basal cell carcinoma it is applied 5 times per week for 6 weeks.

Each single-use sachet contains 250 mg of cream, which is 12.5 mg of imiquimod, and Aldara is packed in boxes of 12 or 24 sachets.

Each question fixes the values needed for its arithmetic. Write the unit beside every step and distinguish applications per week from total weeks. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Read the stated applications per week and the stated number of weeks.
  2. Multiply applications per week by weeks for the sachet count, at one sachet per application.
  3. Multiply the sachet count by 12.5 mg for a total in mg of imiquimod, only when asked.
  4. Keep applications, sachets, weeks and mg separate; convert only when 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 adult uses imiquimod 5% cream for external genital warts, 3 times per week, for the label maximum of 16 weeks, one sachet per application. How many sachets are used in total?

Show the answer

Answer: 48 sachets

Working: 3 applications per week x 16 weeks = 48 applications, one sachet each: 48 sachets.

Question 2

A fictional adult uses imiquimod 5% cream for actinic keratosis, 3 times per week for four weeks, one sachet per application. How many sachets are used, and which pack size covers the course exactly?

Show the answer

Answer: 12 sachets; one box of 12

Working: 3 applications per week x 4 weeks = 12 sachets, which is exactly one 12-sachet box.

Question 3

A fictional patient uses 12 sachets of imiquimod 5% cream over a course. Using the printed content of 12.5 mg of imiquimod per sachet, what total quantity of imiquimod is applied?

Show the answer

Answer: 150 mg

Working: 12 sachets x 12.5 mg = 150 mg of imiquimod in total.

eMC SmPC: Aldara 5% Cream

https://www.medicines.org.uk/emc/product/823/smpc

Where marks are lost

  • Applying the 16-week genital-wart maximum to an actinic keratosis course, which the label fixes at four weeks.
  • Counting 250 mg of cream as 250 mg of imiquimod; each sachet holds 12.5 mg of imiquimod in 250 mg of cream.
  • Assuming daily application; the label regimen is 3 times per week for warts and actinic keratosis, 5 times per week for superficial basal cell carcinoma.

Frequently asked questions

Are these official assessment questions?

No. They are original revision exercises, not official GPhC questions and not for patient care.

Does this calculation decide a real imiquimod course?

No. Follow the stated regimen in the exercise. Real treatment is reviewed for clearance and local skin reactions, with rest periods when needed.

How should I check the answer?

Multiply applications per week by the stated weeks for the sachet count, then by 12.5 mg only when total imiquimod is asked.

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.