Common Registration Assessment, Part 1

Ivermectin 3mg tablet doses by body weight band for the GPhC assessment

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

Published 8 November 2026. Independent revision material, not GPhC questions, not for patient care.

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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 ivermectin 3 mg tablets states that for the treatment of intestinal strongyloidiasis the recommended dosage is one single oral dose of 200 micrograms of ivermectin per kg body weight.

The same information gives a weight-band table for the single dose: 15 to 24 kg one tablet, 25 to 35 kg two tablets, 36 to 50 kg three tablets, 51 to 65 kg four tablets, 66 to 79 kg five tablets, and 80 kg or more six tablets.

For microfilaraemia caused by Wuchereria bancrofti, it states a single oral dose of approximately 150 to 200 micrograms per kg once every 6 months, or 300 to 400 micrograms per kg where treatment can only be given once every 12 months.

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

The method

  1. Match the stated body weight to its band in the label table.
  2. Read off the stated number of 3 mg tablets for that band.
  3. Check the arithmetic: multiply 200 micrograms by the weight in kg, then convert 1000 micrograms to 1 mg.
  4. Keep micrograms, mg, tablets and weight bands 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 patient weighs 40 kg. Using the label weight-band table for ivermectin 3 mg tablets, what single dose is given for intestinal strongyloidiasis?

Show the answer

Answer: Three tablets (9 mg)

Working: 40 kg sits in the 36 to 50 kg band, which is three 3 mg tablets. 3 x 3 mg = 9 mg as a single dose.

Question 2

A fictional patient weighs 70 kg. Using the label weight-band table for ivermectin 3 mg tablets, what single dose is given for intestinal strongyloidiasis?

Show the answer

Answer: Five tablets (15 mg)

Working: 70 kg sits in the 66 to 79 kg band, which is five 3 mg tablets. 5 x 3 mg = 15 mg as a single dose.

Question 3

A fictional patient weighs 60 kg. Calculate 200 micrograms per kg, convert the result to mg, and state the number of 3 mg tablets it equals.

Show the answer

Answer: 12 mg, four tablets

Working: 200 micrograms x 60 kg = 12000 micrograms. 12000 / 1000 = 12 mg. 12 mg / 3 mg = 4 tablets, matching the 51 to 65 kg band.

eMC SmPC: Ivermectin 3 mg, tablets

https://www.medicines.org.uk/emc/product/100011/smpc

Where marks are lost

  • Skipping the micrograms to milligrams conversion, so 12000 micrograms is read as 12000 mg.
  • Reading the wrong row of the weight-band table, such as the 51 to 65 kg row for a 40 kg patient.
  • Mixing up the strongyloidiasis weight-band table with the microfilaraemia mass-treatment schedule.

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 ivermectin dose?

No. Follow the stated weight in the exercise. Real dosing is a single dose set by the label weight-band table for the infection being treated.

How should I check the answer?

Convert micrograms to milligrams first, then match the weight to its band before counting tablets.

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

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More calculation topics

See also the formula sheet, the eight sample questions and the approved calculator page.