Common Registration Assessment, Part 1
Doxazosin standard and slow-release tablets for the GPhC assessment
Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.
Published 18 October 2026. Independent revision material, not GPhC questions, not for patient care.
The NHS lists standard doxazosin tablets in 1 mg, 2 mg, 4 mg and 8 mg strengths, and slow-release tablets in 4 mg and 8 mg strengths.
For high blood pressure the usual dose is 2 mg to 16 mg once a day with standard tablets, or 4 mg to 8 mg once a day with slow-release tablets. Treatment usually starts at 1 mg with standard tablets, and the NHS notes a dose may need more than one tablet, such as two 8 mg tablets for a 16 mg dose.
Each question fixes the values needed for its arithmetic. Write the unit beside every step and keep standard and slow-release forms separate. All prescriptions and patients here are fictional; these are revision materials, not for patient care.
The method
- Identify whether the question supplies standard or slow-release tablets.
- Calculate one dose first; divide prescribed mg by mg per tablet.
- Use more than one tablet per dose when the arithmetic requires it.
- Scale to the stated duration only when a supply is requested.
- Check the total against the stated dose range before reporting it.
Three practice questions
Work each one on paper first, then open the answer. All patients and prescriptions are fictional.
Question 1
A fictional prescription specifies the maximum high blood pressure dose of doxazosin 16 mg once a day using standard 8 mg tablets. How many tablets is one dose?
Show the answer
Answer: 2 tablets
Working: 16 ÷ 8 = 2 tablets once a day.
Question 2
A fictional prescription starts doxazosin at 1 mg once a day using standard 1 mg tablets, increased after a few weeks to 4 mg once a day using 4 mg tablets. How many 4 mg tablets are needed for 28 days at the new dose?
Show the answer
Answer: 28 tablets
Working: 4 ÷ 4 = 1 tablet a day. 1 × 28 = 28 tablets.
Question 3
A fictional prescription specifies doxazosin slow-release 8 mg once a day using 8 mg slow-release tablets. How many tablets are needed for 30 days?
Show the answer
Answer: 30 tablets
Working: 8 ÷ 8 = 1 tablet a day. 1 × 30 = 30 tablets.
Exam approach
Modified-release arithmetic is ordinary division with an extra reading step: confirm the form first, because strengths differ between standard and slow-release.
Where marks are lost
- Mixing standard and slow-release strengths; the forms are not interchangeable in the question.
- Assuming one tablet per dose when the dose needs two.
- Reporting tablets per dose when the question asks for the whole supply.
Frequently asked questions
Are these official assessment questions?
No. They are original revision exercises, not official GPhC questions and not for patient care.
Do I need to memorise the strengths?
The exercise supplies them. In the assessment, read any given product information exactly as written.
How should I check the answer?
Check the requested unit, then work backwards from the quantity to the stated dose and duration.
Sources
- NHS: How and when to take doxazosin
- GPhC, Common Registration Assessment specification and permitted items for 2026
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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See also the formula sheet, the eight sample questions and the approved calculator page.