Common Registration Assessment, Part 1

Alfacalcidol microgram capsules and dose titration steps 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.

One person giving a tablet and a glass of water to another person in bed
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 alfacalcidol 0.25 microgram soft capsules states that the initial dose for adults, adolescents and children over 20 kg bodyweight is 1 microgram per day, that the elderly start at 0.5 micrograms per day, and that children from 6 years of age and under 20 kg bodyweight start at 0.05 micrograms/kg/day.

The same information states that the daily dose may be increased by increments of 0.25 to 0.5 micrograms, that most adult patients respond to doses between 1 and 3 micrograms per day, and that maintenance doses are generally in the range of 0.25 to 1 microgram per day.

It also states that if hypercalcaemia occurs, alfacalcidol should be stopped until plasma calcium returns to normal (approximately 1 week) and then restarted at half the previous dose.

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

The method

  1. Identify the stated patient group and its starting dose rule.
  2. For a child under 20 kg, multiply 0.05 micrograms/kg by the stated weight.
  3. Divide the stated micrograms by the 0.25 microgram capsule strength for the capsule count.
  4. Keep micrograms, micrograms/kg, capsules and dose phases 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 starts alfacalcidol at the label initial dose, using 0.25 microgram capsules. What is the daily dose, and how many capsules is that each day?

Show the answer

Answer: 1 microgram; 4 capsules

Working: The label initial dose for adults is 1 microgram per day. 1 / 0.25 = 4 capsules daily.

Question 2

A fictional child weighs 15 kg and starts alfacalcidol at the label dose for children under 20 kg, using 0.25 microgram capsules. What is the daily dose, and how many capsules is that each day?

Show the answer

Answer: 0.75 micrograms; 3 capsules

Working: 0.05 micrograms/kg x 15 kg = 0.75 micrograms daily. 0.75 / 0.25 = 3 capsules daily.

Question 3

A fictional patient taking alfacalcidol 2 micrograms daily develops hypercalcaemia. According to the label, what happens next, and at what dose is treatment restarted?

Show the answer

Answer: Stop until plasma calcium returns to normal (approximately 1 week), then restart at 1 microgram daily

Working: The label states treatment stops until normocalcaemia (approximately 1 week), then restarts at half the previous dose: 2 / 2 = 1 microgram daily.

eMC SmPC: Alfacalcidol 0.25 microgram soft capsules

https://www.medicines.org.uk/emc/product/14383/smpc

Where marks are lost

  • Applying the 0.05 micrograms/kg rate to an adult; the weight-based rate is only for children from 6 years of age and under 20 kg.
  • Restarting at the full previous dose after hypercalcaemia; the label restarts at half the previous dose.
  • Using the elderly starting dose of 0.5 micrograms for a younger adult, whose label initial dose is 1 microgram daily.

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 alfacalcidol dose?

No. Follow the stated prescription in the exercise. Real dosing is adjusted to plasma calcium, measured weekly at first.

How should I check the answer?

Pick the right starting rule for the stated patient, then divide the microgram dose by 0.25 micrograms per capsule.

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.