Common Registration Assessment, Part 1

Co-careldopa tablet strengths and levodopa daily totals for the GPhC assessment

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

Published 2 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 co-careldopa 25 mg/100 mg tablets explains that each tablet contains 25 mg of carbidopa with 100 mg of levodopa.

For patients new to levodopa, that product information describes a starting schedule of one tablet three times a day, which provides 75 mg of carbidopa a day.

The same information describes increasing the dose gradually, up to a schedule equivalent to eight 25 mg/100 mg tablets a day.

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 stated tablet strength and the doses per day.
  2. Multiply the levodopa content of one tablet by the stated number of tablets a day.
  3. Keep carbidopa and levodopa in separate lines of working when both are asked for.
  4. Multiply the daily tablet count by the stated number of days for a supply.
  5. Keep milligrams and tablets 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 one co-careldopa 25 mg/100 mg tablet three times a day. How much levodopa and how much carbidopa is that each day?

Show the answer

Answer: 300 mg levodopa; 75 mg carbidopa

Working: 100 mg levodopa x 3 tablets = 300 mg; 25 mg carbidopa x 3 tablets = 75 mg.

Question 2

A fictional prescription reads co-careldopa 25 mg/100 mg, one tablet three times a day. How many tablets should be supplied for 28 days?

Show the answer

Answer: 84 tablets

Working: 3 tablets x 28 days = 84 tablets.

Question 3

A fictional patient reaches a schedule of eight co-careldopa 25 mg/100 mg tablets a day. How much levodopa is that each day, and how many tablets is a 7-day supply?

Show the answer

Answer: 800 mg levodopa a day; 56 tablets

Working: 100 mg x 8 tablets = 800 mg; 8 tablets x 7 days = 56 tablets.

eMC SmPC: Co-careldopa 25 mg/100 mg tablets

https://www.medicines.org.uk/emc/product/102159/smpc

Where marks are lost

  • Adding the carbidopa and levodopa contents into a single milligram figure.
  • Reporting the per-dose levodopa instead of the daily total.
  • 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 dose-total calculation justify changing a real dose?

No. Follow the steps in the exercise. Real dose changes are gradual and need 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.