Common Registration Assessment, Part 1

Imipramine oral solution volumes and divided daily doses for the GPhC assessment

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

Published 12 November 2026. Independent revision material, not GPhC questions, not for patient care.

An amber glass medicine bottle without a label
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 Imipramine Hydrochloride 25 mg/5 ml Oral Solution states that each 5 ml contains 25 mg of imipramine hydrochloride.

The same information states that for depression in adults the starting dose is 25 mg up to three times daily, increasing stepwise to 150 to 200 mg, with a usual maintenance of about 50 to 100 mg daily.

The product information states that patients over 60 years should start on 10 mg daily, gradually increasing to 30 to 50 mg daily, and that for nocturnal enuresis in children the bedtime dose ranges from 25 mg at age 6 to 7 up to 50 to 75 mg over age 11, never exceeding 2.5 mg per kg daily.

Each question fixes the values needed for its arithmetic. Write the unit beside every step and convert milligrams to millilitres with the stated 25 mg in 5 ml. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Fix the concentration: 25 mg in 5 ml, which is 5 mg per ml.
  2. Divide the stated milligrams by 25 and multiply by 5 for the volume in ml.
  3. Multiply the per-dose volume by the stated daily frequency for the daily volume.
  4. Apply the stated age-band and 2.5 mg per kg limits for children's doses.
  5. Keep per-dose and per-day volumes on separate lines.

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 imipramine oral solution at 25 mg three times a day. Using the 25 mg/5 ml solution, what volume is each dose and what volume is taken per day?

Show the answer

Answer: 5 ml per dose; 15 ml per day

Working: 25 mg is 1 x 5 ml per dose; 3 doses x 5 ml = 15 ml a day.

Question 2

A fictional adult's dose is increased to 150 mg daily, taken as three divided doses. Using the 25 mg/5 ml solution, what is the daily volume and the volume per dose?

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Answer: 30 ml per day; 10 ml per dose

Working: 150 mg / 25 mg = 6 lots of 5 ml = 30 ml a day; 30 ml / 3 doses = 10 ml per dose.

Question 3

A fictional 9-year-old weighing 30 kg is prescribed 50 mg at bedtime for nocturnal enuresis. Using the 25 mg/5 ml solution, what volume is the dose, and is it within the stated 2.5 mg per kg daily limit?

Show the answer

Answer: 10 ml; yes, the limit allows up to 75 mg

Working: 50 mg / 25 mg = 2 lots of 5 ml = 10 ml. The limit is 2.5 mg x 30 kg = 75 mg, and 50 mg is below 75 mg.

eMC SmPC: Imipramine Hydrochloride 25mg/5ml Oral Solution

https://www.medicines.org.uk/emc/product/13879/smpc

Where marks are lost

  • Treating 25 mg/5 ml as 25 mg per ml instead of 5 mg per ml.
  • Reporting the daily volume when the question asks for the per-dose volume.
  • Skipping the 2.5 mg per kg ceiling when checking a child's dose.

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 imipramine dose?

No. Follow the stated prescription in the exercise. Real dosing follows the prescriber and the product information for the named solution.

How should I check the answer?

Work from 25 mg in 5 ml: divide the milligrams by 25, multiply by 5 for ml, then multiply by the daily frequency if a daily volume 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.