Common Registration Assessment, Part 1
Estradiol patch strengths and twice weekly change counts for the GPhC assessment
Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.
Published 4 November 2026. Independent revision material, not GPhC questions, not for patient care.
The manufacturer's UK product information for Evorel patches states that the patch is applied to the skin twice weekly, with each patch delivering a stated amount of estradiol per 24 hours.
The same information states that treatment of oestrogen deficiency symptoms should be started with one Evorel 50 patch delivering 50 micrograms of estradiol per 24 hours, with the dose adjusted after the first month if necessary.
It also states that a maximum dose of 100 micrograms of estradiol per 24 hours should not be exceeded.
Each question fixes the values needed for its arithmetic. Write the unit beside every step and distinguish a patch strength from a daily delivery or a supply period. All prescriptions and patients here are fictional; these are revision materials, not for patient care.
The method
- Identify the stated patch strength in micrograms per 24 hours.
- Count patch changes per week from the twice-weekly schedule.
- Multiply the weekly change count by the stated number of weeks for a supply quantity.
- Keep micrograms, patches and weeks 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 uses an Evorel 50 patch changed twice weekly. How many patches are needed for 28 days?
Show the answer
Answer: 8 patches
Working: 28 days / 7 days = 4 weeks. Two patches each week x 4 weeks = 8 patches.
Question 2
A fictional patient wears an Evorel 50 patch delivering 50 micrograms of estradiol per 24 hours. How many micrograms are delivered over seven days?
Show the answer
Answer: 350 micrograms
Working: 50 micrograms per 24 hours x 7 days = 350 micrograms in a week.
Question 3
A fictional prescription for Evorel 50 patches, changed twice weekly, runs for 12 weeks. How many patches should be supplied?
Show the answer
Answer: 24 patches
Working: Two patches each week x 12 weeks = 24 patches.
eMC SmPC: Evorel 50 patches
https://www.medicines.org.uk/emc/product/10927/smpc
Where marks are lost
- Treating micrograms per 24 hours as the number of patches per day.
- Using one patch each day when the stated schedule is twice weekly.
- Forgetting to convert a 28-day period into four weeks before counting patches.
Frequently asked questions
Are these official assessment questions?
No. They are original revision exercises, not official GPhC questions and not for patient care.
Does twice weekly mean two patches in every seven-day week for these exercises?
Yes. Use two patch changes per week when the question states a twice-weekly schedule.
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.
Practise until the method is automatic
Try 15 free questions with worked answers. No sign-up required.
More calculation topics
- Dose by weight calculations for the GPhC assessment
- Volume to give: liquid medicine calculations
- Percentage strength calculations: w/v, w/w and ratios
- Dilution calculations with C1V1 = C2V2
- Infusion rate calculations in mL per hour
- Drip rate calculations: drops per minute
- Body surface area calculations
- Creatinine clearance (Cockcroft-Gault) calculations
- Moles and millimoles calculations
- Displacement volume calculations for reconstitution
- Quantity to supply calculations
- Using a provided formula in calculations
- Dose information from packaging and labels
- Diluting a stock to a lower strength
- Medicine cost and switch calculations
- Rounding rules in calculations
- Enteral feed rate calculations
- Electrolyte content over time
- Infusion dose per kg per hour
- Rounding doses to measurable volumes
- Relative risk and relative risk reduction
- Absolute risk reduction and number needed to treat
- Odds ratio and confidence intervals
- Relative versus absolute risk reduction
- Loading dose and volume of distribution
- Top-up doses from measured drug levels
- Salt correction factors
- Mass and molar drug concentrations
- Half-life and falling drug levels
- Steady-state concentration and infusion rate
- Bioavailability and equivalent oral doses
- Oral maintenance dose and dosing interval
- Elimination rate constant and half-life
- Accumulation towards steady state
- Ratio strengths and one in X
- Serial dilution factors
- Mixing solutions of different strengths
- Tablet quantities for reducing regimens
- Equivalent doses from provided conversion tables
- Thresholds and dose-banding algorithms
- Unit conversions for mass and volume
- Units and units per mL
- Reconstituting powders and final concentration
- Millimoles and milliequivalents
- Infusion time and volume remaining
- Days supply from pack sizes
- Percentage w/v and w/w conversions
- Ideal and adjusted body weight from formulae
- Diluting creams and ointments by weight
- Scaling a formula to a batch size
- Age-band doses from a provided table
- Tablet fractions and split doses
- Stones, pounds, inches and metric conversions
- Micrograms per minute from mg per hour
- Percentage change and mark-up
- Molar solutions and mass per volume
- Osmolarity from component concentrations
- Direct proportion and cross-multiplication
- Scientific notation and very small quantities
- Stock use and reorder quantities
- Parts per million and very dilute solutions
- Sodium chloride equivalents and isotonic solutions
- Density and specific gravity conversions
- Doses per day and hours between doses
- Finding the volume of diluent to add
- Capping a dose at a stated maximum
- Whole vials and ampoules to draw up
- Reading values from a provided graph
- Micrograms per kg per minute infusions
- Percentage composition of a compound preparation
- Suppository displacement values
- Isotonicity by freezing point depression
- Energy content of parenteral nutrition
- Syringe driver rate calculations
- Area under the curve calculations
- Renal dose adjustments using provided bands
- Insulin units and infusion calculations
- Working backwards from a stated dose
- Doses and days from multi-dose devices
- Combined additives in one infusion
- BMI calculations for the GPhC assessment
- Fewest tablets to make a dose
- Clearance from half-life and volume of distribution
- Maintenance fluid requirements by weight
- Sodium load from effervescent tablets
- Ethanol content of liquid preparations
- Oxygen cylinder duration calculations
- Urine output and fluid balance calculations
- Quantities for titration packs
- Infusion line priming and dead space
- Alcohol unit calculations for the GPhC assessment
- Paracetamol syrup calculations for children
- Ibuprofen liquid calculations for children
- Vitamin D conversions for the GPhC assessment
- Ferrous sulfate drops and tablet calculations
- Amoxicillin liquid and capsule calculations
- Folic acid dose and quantity calculations
- Adult paracetamol and the daily maximum
- Calcium and iron intake calculations
- Salt limit calculations by age
- Fingertip unit calculations for the GPhC assessment
- Adrenaline dose calculations for anaphylaxis
- Breakthrough opioid dose calculations
- IV fluid bolus calculations in children
- Neonatal maintenance fluid calculations
- Enoxaparin dose calculations by weight
- Levothyroxine dose by weight calculations
- Methotrexate weekly dose calculations
- Sensitivity, specificity and predictive value calculations
- Hypertonic saline bolus calculations in children
- Prednisolone tablet and liquid calculations for the GPhC assessment
- Cetirizine liquid volume and supply calculations for the GPhC assessment
- Lactulose dose and bottle supply calculations for the GPhC assessment
- Metformin tablet and liquid strength calculations for the GPhC assessment
- Flucloxacillin capsule and course supply calculations for the GPhC assessment
- Clarithromycin liquid strength and formulation calculations for the GPhC assessment
- Senna tablet and syrup quantity calculations for the GPhC assessment
- Nitrofurantoin formulation and course quantity calculations for the GPhC assessment
- Aciclovir five-times-daily course calculations for the GPhC assessment
- Oral rehydration fluid deficit calculations for the GPhC assessment
- Warfarin tablet strengths and daily doses for the GPhC assessment
- Digoxin microgram tablets and daily doses for the GPhC assessment
- Co-amoxiclav tablet courses and liquid shelf life for the GPhC assessment
- Phenoxymethylpenicillin age band doses and liquid strengths for the GPhC assessment
- Cefalexin capsule counts and course supply for the GPhC assessment
- Co-codamol strengths and 24-hour maximums for the GPhC assessment
- Trimethoprim tablets, liquid and course lengths for the GPhC assessment
- Macrogol sachet schedules and water volumes for the GPhC assessment
- Colchicine tablet counts and course maximums for the GPhC assessment
- Furosemide tablet and liquid strengths for the GPhC assessment
- Amitriptyline tablet strengths and daily doses for the GPhC assessment
- Ramipril titration packs and tablet strengths for the GPhC assessment
- Amlodipine tablet and liquid strengths for the GPhC assessment
- Atorvastatin tablet strengths and daily doses for the GPhC assessment
- Citalopram drops and tablet equivalents for the GPhC assessment
- Fexofenadine tablet strengths by age for the GPhC assessment
- Gliclazide standard and slow-release tablets for the GPhC assessment
- Lansoprazole capsule strengths and course lengths for the GPhC assessment
- Naproxen tablet strengths and daily maximums for the GPhC assessment
- Propranolol tablet strengths and daily doses for the GPhC assessment
- Fluoxetine capsule strengths and liquid doses for the GPhC assessment
- Simvastatin tablet strengths and evening doses for the GPhC assessment
- Losartan tablet strengths and daily doses for the GPhC assessment
- Gabapentin capsules, tablets and three daily doses for the GPhC assessment
- Montelukast tablets, chewables and granules by age for the GPhC assessment
- Salbutamol inhaler puffs and daily maximums for the GPhC assessment
- Mirtazapine tablets, liquid and bedtime doses for the GPhC assessment
- Allopurinol tablet strengths and daily doses for the GPhC assessment
- Spironolactone tablet strengths by condition for the GPhC assessment
- Doxazosin standard and slow-release tablets for the GPhC assessment
- Omeprazole capsule strengths and daily doses for the GPhC assessment
- Sertraline tablet strengths and dose steps for the GPhC assessment
- Bisoprolol tablet strengths and daily doses for the GPhC assessment
- Doxycycline capsule strengths and course totals for the GPhC assessment
- Pregabalin capsule strengths and daily doses for the GPhC assessment
- Tramadol capsule strengths and daily maximums for the GPhC assessment
- Venlafaxine tablet strengths and daily doses for the GPhC assessment
- Clopidogrel tablet strengths and supply counts for the GPhC assessment
- Bendroflumethiazide tablet strengths and daily doses for the GPhC assessment
- Tamsulosin capsule strengths and daily doses for the GPhC assessment
- Candesartan tablet strengths and daily doses for the GPhC assessment
- Apixaban tablet strengths and twice-daily doses for the GPhC assessment
- Rivaroxaban tablet strengths and daily doses for the GPhC assessment
- Escitalopram tablet strengths and daily doses for the GPhC assessment
- Duloxetine capsule strengths and daily doses for the GPhC assessment
- Indapamide tablet strengths and morning doses for the GPhC assessment
- Empagliflozin tablet strengths and daily doses for the GPhC assessment
- Semaglutide weekly injection dose steps for the GPhC assessment
- Rosuvastatin tablet strengths and daily doses for the GPhC assessment
- Codeine tablet strengths and daily maximums for the GPhC assessment
- Lisinopril tablet strengths and daily doses for the GPhC assessment
- Dapagliflozin tablet strengths and once-daily doses for the GPhC assessment
- Atenolol tablet strengths and daily doses for the GPhC assessment
- Metronidazole tablet strengths and course quantities for the GPhC assessment
- Azithromycin tablet strengths and short courses for the GPhC assessment
- Alendronic acid weekly tablets and supply for the GPhC assessment
- Carbimazole tablet strengths and titration doses for the GPhC assessment
- Hydroxychloroquine tablet strengths and weight-based maximums for the GPhC assessment
- Bumetanide tablet strengths and daily doses for the GPhC assessment
- Fluconazole capsule strengths and single doses for the GPhC assessment
- Sitagliptin tablet strengths and once-daily doses for the GPhC assessment
- Valsartan tablet strengths and daily doses for the GPhC assessment
- Ciprofloxacin tablet strengths and twice-daily courses for the GPhC assessment
- Sumatriptan tablet strengths and repeat-dose maximums for the GPhC assessment
- Morphine sulfate oral solution volumes and 4-hourly doses for the GPhC assessment
- Carvedilol tablet strengths and titration steps for the GPhC assessment
- Ezetimibe tablet strength and once-daily doses for the GPhC assessment
- Quetiapine tablet strengths and titration days for the GPhC assessment
- Loratadine tablet strength and once-daily doses for the GPhC assessment
- Baclofen tablet strengths and three daily doses for the GPhC assessment
- Paroxetine tablet strengths and morning doses for the GPhC assessment
- Nortriptyline tablet strengths and nightly doses for the GPhC assessment
- Zopiclone tablet strengths and bedtime doses for the GPhC assessment
- Diazepam tablet strengths and divided daily doses for the GPhC assessment
- Finasteride tablet strengths and once-daily doses for the GPhC assessment
- Aripiprazole tablet strengths and once-daily doses for the GPhC assessment
- Lamotrigine tablet strengths and titration steps for the GPhC assessment
- Levetiracetam tablet strengths and twice-daily steps for the GPhC assessment
- Co-amoxiclav tablet strengths and three daily doses for the GPhC assessment
- Donepezil tablet strengths and bedtime doses for the GPhC assessment
- Cyclizine tablet strengths and three daily doses for the GPhC assessment
- Promethazine tablet and liquid dose volumes for the GPhC assessment
- Metoclopramide tablet strengths and five-day courses for the GPhC assessment
- Tranexamic acid tablet counts and course days for the GPhC assessment
- Hydroxocobalamin injection loading course counts for the GPhC assessment
- Lithium tablet strengths and daily doses for the GPhC assessment
- Risperidone liquid volumes and titration steps for the GPhC assessment
- Carbamazepine liquid volumes and daily doses for the GPhC assessment
- Diltiazem tablet strengths and three daily doses for the GPhC assessment
- Prochlorperazine tablet and buccal dose counts for the GPhC assessment
- Verapamil tablet and liquid dose volumes for the GPhC assessment
- Perindopril tablet strengths and morning doses for the GPhC assessment
- Oxybutynin tablet strengths and maximum daily doses for the GPhC assessment
- Domperidone tablet counts and short courses for the GPhC assessment
- Pantoprazole tablet strengths and course lengths for the GPhC assessment
- Cefalexin capsule strengths and course quantities for the GPhC assessment
- Clarithromycin tablet strengths and twice-daily courses for the GPhC assessment
- Melatonin slow-release tablet counts and courses for the GPhC assessment
- Metoprolol tablet strengths and divided daily doses for the GPhC assessment
- Zolpidem tablet strengths and bedtime doses for the GPhC assessment
- Trazodone tablet strengths and bedtime doses for the GPhC assessment
- Esomeprazole capsule strengths and daily doses for the GPhC assessment
- Lorazepam tablet strengths and short courses for the GPhC assessment
- Olanzapine tablet strengths and once daily doses for the GPhC assessment
- Solifenacin tablet strengths and once daily doses for the GPhC assessment
- Latanoprost eye drop counts and bottle supply for the GPhC assessment
- Loperamide capsule counts and daily maximums for the GPhC assessment
- Topiramate tablet strengths and titration steps for the GPhC assessment
- Sodium valproate daily doses and tablet counts for the GPhC assessment
- Tolterodine twice daily and slow-release doses for the GPhC assessment
- Mirabegron slow-release tablets and once daily doses for the GPhC assessment
- Anastrozole 1mg tablets and long-term courses for the GPhC assessment
- Sulfasalazine 500mg tablets and daily dose steps for the GPhC assessment
- Varenicline starter titration and 12-week courses for the GPhC assessment
- Letrozole 2.5mg tablets and daily courses for the GPhC assessment
- Eplerenone 25mg and 50mg tablet doses for the GPhC assessment
- Dipyridamole twice daily capsules and tablet doses for the GPhC assessment
- Lymecycline 408mg capsules and acne course lengths for the GPhC assessment
- Ropinirole tablet strengths and weekly dose steps for the GPhC assessment
- Sotalol tablet strengths and daily doses for the GPhC assessment
- Nefopam 30mg tablets and daily doses for the GPhC assessment
- Acrivastine 8mg capsules and daily maximums for the GPhC assessment
- Gaviscon liquid doses and daily maximums for the GPhC assessment
- Clonidine tablet and liquid strengths and daily doses for the GPhC assessment
- Low-dose aspirin 75mg tablets and daily supply for the GPhC assessment
- Carbocisteine capsules, sachets and liquid doses for the GPhC assessment
- Co-dydramol strengths and 24-hour tablet maximums for the GPhC assessment
- Medroxyprogesterone tablet strengths and course days for the GPhC assessment
- Hydrocortisone tablet strengths and divided daily doses for the GPhC assessment
- Dexamethasone daily doses and tablet counts for the GPhC assessment
- Tiotropium inhaler puffs and monthly capsule supply for the GPhC assessment
- GTN spray and tablet doses during angina attacks for the GPhC assessment
- Isosorbide mononitrate tablet doses and daily maximums for the GPhC assessment
- Thiamine tablet strengths and daily doses for the GPhC assessment
- Fybogel sachet doses and water volumes for the GPhC assessment
- Chlorphenamine 4mg tablets and 24-hour maximums for the GPhC assessment
- Diclofenac tablet daily doses and gel application limits for the GPhC assessment
- Bisacodyl tablet and suppository doses for the GPhC assessment
- Cinnarizine 15mg tablets and travel sickness doses for the GPhC assessment
- Hyoscine hydrobromide 300 microgram tablets and daily maximums for the GPhC assessment
- Fentanyl patch strengths and 3-day change intervals for the GPhC assessment
- Buprenorphine patch release rates and change intervals for the GPhC assessment
- Pseudoephedrine tablet and liquid doses in 24 hours for the GPhC assessment
- Fluticasone inhaler puffs, nebule doses and steroid cards for the GPhC assessment
- Beclometasone inhaler puffs and daily puff maximums for the GPhC assessment
- Peppermint oil capsules daily doses and timing for the GPhC assessment
- Mometasone nasal spray sprays per nostril and daily limits for the GPhC assessment
- Nystatin liquid doses and daily frequency for the GPhC assessment
- Clotrimazole pessary strengths and course nights for the GPhC assessment
- Fusidic acid cream applications and eye drop doses for the GPhC assessment
- Terbinafine tablet doses and course weeks by infection for the GPhC assessment
- Orlistat capsules three times daily and meal timing for the GPhC assessment
- Colecalciferol IU doses and weekly loading schedules for the GPhC assessment
- Methadone liquid daily doses and millilitre volumes for the GPhC assessment
- Chloramphenicol eye drops and ointment 5-day courses for the GPhC assessment
- Memantine weekly titration steps and liquid pump doses for the GPhC assessment
- Ticagrelor loading doses and twice-daily tablet counts for the GPhC assessment
- Mesalazine tablets, granules and divided daily doses for the GPhC assessment
- Tadalafil daily and on-demand tablet doses for the GPhC assessment
- Nortriptyline tablet and liquid strengths and daily doses for the GPhC assessment
- Nifedipine modified-release tablets and once daily doses for the GPhC assessment
- Nicorandil tablet strengths and twice daily doses for the GPhC assessment
- Azathioprine tablet strengths and weight-based doses for the GPhC assessment
- Mebeverine tablets three times daily and capsule doses for the GPhC assessment
- Oxycodone immediate and modified-release doses for the GPhC assessment
- Dihydrocodeine modified-release tablets and twelve hourly doses for the GPhC assessment
- Sildenafil tablet timing and the one tablet daily limit for the GPhC assessment
- Cyanocobalamin tablet doses and daily micrograms for the GPhC assessment
- Timolol eye drop strengths and drops per day for the GPhC assessment
- Clobetasol 0.05% cream amounts and weekly gram limits for the GPhC assessment
- Ondansetron 4 mg and 8 mg tablets and five day courses for the GPhC assessment
- Amiodarone loading schedule and maintenance tablet counts for the GPhC assessment
- Valaciclovir 500 mg tablets and shingles course counts for the GPhC assessment
- Celecoxib 100 mg and 200 mg capsules and daily doses for the GPhC assessment
- Lisdexamfetamine capsule strengths and morning doses for the GPhC assessment
- Risedronate daily 5 mg and weekly 35 mg tablet counts for the GPhC assessment
- Co-careldopa tablet strengths and levodopa daily totals for the GPhC assessment
- Felodipine prolonged-release tablets and once daily doses for the GPhC assessment
- Lercanidipine 10 mg and 20 mg tablets and morning doses for the GPhC assessment
- Erythromycin 250 mg and 500 mg tablets and daily totals for the GPhC assessment
- Phenytoin capsule counts and mg per kg daily doses for the GPhC assessment
- Dabigatran capsule strengths and twice daily doses for the GPhC assessment
- Rivastigmine patch strengths and the titration schedule for the GPhC assessment
- Clonazepam tablet strengths and titration doses for the GPhC assessment
- Methylphenidate immediate-release tablets and divided doses for the GPhC assessment
- Pramipexole microgram tablets and weekly titration steps for the GPhC assessment
- Atomoxetine capsule doses and mg per kg titration for the GPhC assessment
- Flecainide tablet doses and twice daily maximums for the GPhC assessment
- Etoricoxib tablet doses by indication and daily maximums for the GPhC assessment
- Ivabradine tablet doses and twice daily titration for the GPhC assessment
- Edoxaban tablet strengths and once daily doses for the GPhC assessment
- Liraglutide daily injection dose steps and pen supply for the GPhC assessment
- Pravastatin tablet strengths and evening doses for the GPhC assessment
- Docusate 100 mg capsules and divided daily doses for the GPhC assessment
- Betahistine tablet strengths and three daily doses for the GPhC assessment
- Theophylline modified-release tablets and twelve hourly doses for the GPhC assessment
- Lidocaine 700 mg medicated plasters and daily limits for the GPhC assessment
- Galantamine prolonged-release capsules and titration steps for the GPhC assessment
- Febuxostat 80 mg and 120 mg tablets and daily doses for the GPhC assessment
See also the formula sheet, the eight sample questions and the approved calculator page.