LPN INTENSIVE CALCULATIONS�� MODULE FOUR (4)��� INTENSIVE GPHC Exam revision � programme

LONDON PHARMACIST NETWORK (LPN)

THE HOME OF GPHC PHARMACY CALCULATIONS !!!!

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OPENING REMARKS

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• Book sign means resource questions
• USE LAPTOP OR DESKTOP
• CALC SESSION 4 of 10
• GET CALCULATOR. GET NOTES PAD and PEN
• PAID REVISION SESSION so , DO NOT SHARE LINK/ MATERIALS for this session.
• MENTAL BREAK 5 – 10 MINS
• YOU WILL BE SENT PRACTICE QUESTIONS AFTER SESSION
• STAY ACTIVE ATTEMPT QUESTIONS AND ASK QUESTIONS

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TODAY’S TOPICS

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• INCREASE IN DAILY OPIOID DOSES✅
• RELATIVE RISK ✅
• MASS, MOLAR, MR ✅
• RDA OF SODIUM ✅
• ROTIGOTINE PATCHES ✅

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DAILY OPIOID DOSES

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• Patients may need an increase in daily opioid dose due to worsening of their condition.
• maximum = ½
• Minimum = 1/3
• Mr. A takes Zomorph 60mg m/r capsule twice a day. He also take oramorph 10mg/5ml at a dose 5ml every four hours

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QUESTION 1

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• Mr. D a 50-year-old man is finding it hard to swallow his morphine tablets. He takes sevredol tablets 20mg every 8 hours per day and he also takes 5ml oramorph 10mg/5ml every four hours for breakthrough pain . You have been instructed to switch Mr. D to fentanyl patches. What is the correct strength of fentanyl patches you would recommend ? Use the resource below.

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• Prescribing in palliative care | Medicines guidance | BNF | NICE

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QUESTION 1 ANSWER

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• oramorph 10mg = 5ml
• He takes 30ml which is = 60mg
• Sevredol 20mg x 3 = 60mg
• Total morphine = 120mg per day

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• Use resource
• 120mg daily = 50mcg patch

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QUESTION 2

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• Mrs. J. a 56-year-old patient takes OXYCODONE 10mg tablets. She take one at 5AM, 11AM, 5PM AND 11PM EVERY DAY. Her doctor would like to switch her to fentanyl transdermal patches. Use the resource provided to decide which strength of patch you will provide.

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QUESTION 2

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• Mrs. J. a 56-year-old patient takes OXYCODONE 10mg tablets. She take one at 5AM, 11AM, 5PM AND 11PM EVERY DAY.
• Her doctor would like to switch her to fentanyl transdermal patches. Use the resource provided to decide which strength of patch you will provide.
• Write your answer on your answer sheet.

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• ANSWER = 25 mcg patches

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QUESTION 3

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• An elderly patient takes metoclopramide 10mg , paracetamol 500mg PRN and MST 100mg continuous every day. She also takes 8ml of oramorph oral solution 10mg/5ml QDS for breakthrough pain. What is the maximum dose of morphine she can have per day if her GP decides to increase her dose ?
• ANSWER TO NEAREST TEN.

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QUESTION 3

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• 100 + 64 = 164MG 

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• 50% of 164 = 82

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• 164 + 82 = 246 mg per day

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• ANSWER = 250 mg

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QUESTION 4

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• Mr. D. a 70-year-old male patient takes TRAMADOL 100MG TDS , metformin 500mg BD , zomorph 60mg in the morning and one sevredol 10mg QDS. She also takes 8ml of oramorph oral solution 10mg/5ml QDS for breakthrough pain. What is the minimum dose of morphine she can have per day if her GP decides to increase her dose ?
• Answer in mg to nearest 5mg. Link below
• Prescribing in palliative care | Medicines guidance | BNF | NICE

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QUESTION 4

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• 30mg plus 60mg plus 40mg plus 64mg = 194MG 

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• 1/ 3 of 194 = 64.6667

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• 194 + 64.6667 = 258.67 mg per day

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• ANSWER = 260mg

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RELATIVE RISK

• Relative risk (RR) is a measure that compares the risk of an outcome in an exposed or treatment group to the risk of the same outcome in an unexposed or control group.

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• RR formula = Risk in the exposed group

Risk in the control group

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• What it tells you

• RR = 1 → No difference in risk between groups

• RR < 1 → The exposure reduces risk (protective effect)

• RR > 1 → The exposure increases risk (harmful effect)

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RELATIVE RISK - QUESTION 1

You are asked to carry out a study which investigates the association between smokers and lung cancer. Over a 5-year period, two groups of patients over 60 years were studied. One group contained smokers whilst the other group was made up of non-smokers. Calculate the relative risk of smokers to develop lung cancer based on the results in the table below.

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RELATIVE RISK - ANSWER 1

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• Smokers: 80 lung cancer cases / 1000 participants = 0.08
• Non-smokers: 20 lung cancer cases / 1000 participants = 0.02

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• RR = 0.08 / 0.02 = 4

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• Smokers are 4 times more likely to develop lung cancer compared to non-smokers.

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• Answer: RR = 4

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RELATIVE RISK - QUESTION 2

A clinical trial investigates whether Fluvac vaccine reduces the risk of developing symptomatic influenza compared with no treatment. A total of 1,200 adults were enrolled and evenly assigned to one of two groups. Calculate the relative risk (RR) of developing influenza in the Fluvac group compared with the placebo group. Give your answer to 2 decimal places.

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RELATIVE RISK - ANSWER 2

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• FLUVAC : 48 influenza cases / 600 total participants = 0.08
• PLACEBO: 120 influenza cases / 600 total participants = 0.2

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• RR = 0.08 / 0.2 = 0.40

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• Answer: RR = 0.40

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RELATIVE RISK - QUESTION 3

A public health team evaluates whether a new smoking‑cessation programme reduces the risk of developing chronic obstructive pulmonary disease (COPD) over 5 years. A total of 2,400 smokers were enrolled and randomly assigned to one of two groups: ANSWER TO 2.D.P

• Intervention group: Received the new cessation products

• Control group: Received standard advice only

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RELATIVE RISK - ANSWER 3

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• NRT : 96 / 1200 total participants = 0.08
• STANDARD ADVICE: 168 / 1200 total participants = 0.14

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• RR = 0.08 / 0.14 = 0.57

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• Answer: RR = 0.57

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MASS /MOLES/M.R. – RULES

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FOUR RULES TO FOLLOW

• 1. FORMULA is Mole = Mass/Mr
• 2. MMOL = mass in mg and MOLE = mass in grams
• 3. Use the formula twice to find the weight of an element within a compound E.g. Na in NaCl
• 4. Ensure you factor in the number of atoms within each molecule of a compound. E.g. CaCl2 , 2. KHC03

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SAMPLE QUESTION -

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• MR. V . is receiving 40 mmol of sodium carbonate four times a day as advised by his doctor.
• Calculate the amount of sodium carbonate he receives per daily dose. The drug formula is provided below.
• Na = 23 C = 12 0 = 16
• Na2CO3
• Answer in g as a whole number

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SAMPLE ANSWER -

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• MR = 106g/mol
• Formula = mmol = mass/mr
• 40mmol x 4 = 160 mmol per day
• 160 = Mass / 106
• Mass = 106 x 160 = 16960mg
• 17 g ANSWER

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QUESTION 1- MASS,MOLES,MR

A 58-year-old female patient requires sodium citrate for cystitis treatment . Note that when a sachet is dissolved in 200ml water, the following electrolytes and their content in mg are found within.

Glucose=325mg,

Sodium=277mg,

Na+ RMM is 23g/mol.

How many mmols of sodium are available in a 1 litre solution?

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Answer to 1 d.p.

• LONDON PHARMACIST NETWORK INTENSIVE CALCULATIONS

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QUESTION 1 ANSWER – MASS, MOLES

Mole = mass/ Mr

Mmol = 277 / 23

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12.04mmol = 200ml

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12.04 x 5 = 60.21mmol in 1000ml

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ANSWER = 60.2MMOL

QUESTION 2- MASS,MOLES,MR

• Mr T. takes digoxin and requires regular serum potassium monitoring. This morning a member of staff hands you five 10ml blood samples for Mr. T. Each sample contains 9mg of potassium. From the samples you have been given, calculate the patient’s total serum potassium concentration. K=39g/mol. Express your answer in mmol/L .
• Answer to 1.d.p.

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ANSWER 2 -

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• 9mg X 5 = 45mg
• 45/39 = 1.1538 mmol
• 1.1538 = 50ml
• 23.076 = 1000 ml
• Answer = 23.1 mmol/ L

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QUESTION 3- MASS,MOLES,MR

Mr. P suffered two hyponatremic convulsions within the last 90 days . His blood test shows that his serum sodium level is 120mmol/L. This could be a possible cause of his seizures. He is due to receive sodium via infusion. The only strength of sodium bags available to you is 3.5%w/v which will be given as 5ml per kg every 5 minutes as per the consultant’s request.

• Mr. P is 165cm tall and weighs 140 lbs.
• Based on the information given about Mr. P, how much sodium in grams will he receive after a period of 120 minutes ?
• ANSWER to 1.d.p
• 1lb = 0.45kg

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ANSWER 3-

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• 3.5%w/v = 3.5g = 100ml
• 140 lbs = 63 kg
• 5ml = 0.175g
• 5ml/kg = 0.175 x 63kg = 11.025g
• So, 11.025g every 5 minutes
• 120 minutes = 264.6g
• ANSWER = 264.6g

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QUESTION 4- MASS,MOLES,MR

Mr. Paul is a 69-year-old man who is receiving treatment with sodium bicarbonate . He is taking sodium bicarbonate 5%w/v oral solution at 20ml twice a day. The molecular formula for sodium bicarbonate is Na2CO3. The molecular weights are

Na - 23g/mol

Carbon 12g/mol

Oxygen 16g/mol

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What quantity of sodium will Mr. Paul receive per day, give your answer in mg to one decimal place.

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ANSWER 4-

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• MR = 106
• MOLE = Mass/ Mr
• Mole = 2g/106
• Mole = 0.01886792
• Mass of sodium = 0.01886792 x 46= 0.86792g
• Mg = 867.9mg ANSWER

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QUESTION 1 - RDA

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An elderly patient takes Acidex oral suspension for heartburn and indigestion. However, his doctor is concerned about his sodium intake levels. He takes 10ml of Acidex oral suspension with his breakfast, with lunch and dinner. Given that each 5ml of Acidex oral suspension contains 133.5mg of sodium bicarbonate, Calculate the percentage of his sodium RDA he takes via a daily dose of Acidex. Answer the nearest whole number.

NB

RDA of sodium = 2.4g (6g of salt)

Sodium bicarbonate = NaHC03

Na = 23, H = 1, C = 12, O = 16

London Pharmacist Network intensive GPhc exam calculations

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ANSWER 1 R.D.A

5ml of Acidex oral suspension contains 133.5mg of sodium bicarbonate

30ml per day = 801mg of sodium bicarbonate

Mmol = mass/ Mr

Mmol = 801 / 84 = 9.5357mmol

9.5357 x 23 = 219.3211mg

219.32/ 2400 x 100 = 9.138

ANSWER = 9%

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R.D.A QUESTION 2

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• Miss. V a-9-year-old patient has been prescribed phenytoin 20mg/5ml solution at a dose of 0.5mg/kg twice daily . Every 5ml of Phenytoin solution contains 2.2mmol of sodium. The child weighs 70 lbs . Given that the RDA of NaCl for a child is 3g (1.2g sodium) .
• Calculate the % RDA of sodium in her daily sodium intake from phenytoin .units =1 lb = 0.45kg

Na = 23, Cl = 35.5 , NaCl = 58.5

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Answer to 1 D.P.

LONDON PHARMACIST NETWORK INTENSIVE CALCULATIONS

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R.D.A QUESTION 2 ANSWER

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0.5mg per kg

0.5mg x 31.5kg = 15.75mg

15.75mg x 2 = 31.5mg per DAY

20mg = 5ml

31.5mg = 7.875 ml

5ml = 2.2 mmol then 7.875 = 3.465 mmol

3.465 mmol x 23 = 79.695mg i.e 0.079695g

0.079695/1.2 x 100 = 6.64125%

ANSWER = 6.6%

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R.D.A QUESTION 3

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• Mrs. T. a-59-year-old patient has been started on sodium valproate 200mg M/R tablets today at the recommended starting dose. See resource link below.
• Assume each tablet contains 8mmol of sodium.
• Given that the RDA of NaCl for an adult is 6g (2.4g sodium) .
• Calculate the % RDA of sodium in his daily sodium intake from the drug assuming he takes the starting daily dose allowed.
• Answer as whole number
• Na = 23, Cl = 35.5 , NaCl = 58.5
• Sodium Valproate 200mg Gastro-Resistant Tablets - Summary of Product Characteristics (SmPC) - (emc) | 1496

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QUESTION 3 ANSWER

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STARTING DOSE = 600mg daily

1 TAB TDS = 3 tabs

1 tab = 8mmol

then 3 tabs = 24 mmol

Mmol = mass/ MR

MR = 23mg/mmol

24 mmol x 23 = 552mg i.e. 0.552g

0.552/2.4 x 100 = 23%

ANSWER = 23%

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QUESTION 1

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Mrs. S. is an 81-year-old Parkinson’s disease patient who needs to be switched to rotigotine patches. She currently takes

• Sinemet, one tablet QDS
• Ropinirole 7mg every day.

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Calculate what strength of rotigotine patches, Miss S should be prescribed every 24 hours.

Use resource provided on the next page.

• LONDON PHARMACIST NETWORK INTENSIVE CALCULATIONS

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ROTIGOTINE PATCH RESOURCE

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FORMULA

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QUESTION 1 ANSWER

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Step 1 = 50 x 4 = 200mg of levodopa

Step 2 = convert Ropinirole to levodopa

Step 3 = if 8mg = 160mg of levodopa then 7mg = 140mg

Step 4 = 200 + 140 = 340

Step 5 = 340/100 = 3.4mg

ANSWER =Supply 4mg rotigotine patches

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QUESTION 2

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Mr. Eddy is a 72-year-old Parkinson’s disease patient who needs to be switched to rotigotine patches. He currently takes

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Half Sinemet CR capsules 1 TDS

Entacapone 100mg tablets 1 TDS

Donepezil 5mg tablets every evening.

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Using the resource provided on the next page.

Calculate what strength of rotigotine patches, this patient should be prescribed every 24 hours.

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QUESTION 2 ANSWER

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Step 1 - 100 x 3 = 300mg

Step 2 - 300mg x 0.7 X1.3 = 273mg

Step 3 – 0 Dopamine agonist = 0

Step 4 - 273 + 0 = 273

Step 5 - 273 x 0.55 = 150.15 mg

150.15/20 = 7.5075mg

ANSWER =Supply 8mg ropinirole patches

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QUESTION 3

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• Miss P is a 60-year-old Parkinson’s disease patient who needs to be switched to rotigotine patches. She currently takes
• Co-beneldopa 25/250 capsules 1 TDS
• Entacapone 100mg tablets – 1 TDS
• Cabergoline 2mg tablets every evening.
• Calculate what strength of rotigotine patches, Miss P should be prescribed every 24 hours
• Resource is provided

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ANSWER 3

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• first step - 250 x 3 = 750mg
• Step 2 - 750mg x 1.3 = 975
• Step 3 - 2 x100 = 200mg
• 975 + 200 = 1175
• Step 4 - 1175 x 0.55 = 646.25 mg
• 646.25/20 = 32.3125
• ANSWER = 16mg MAX ROTIGOTINE patches

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THE END

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