Drug Calculations for Nurses First edition by Kerri Wright

Drug Calculations for Nurses
First edition
by Kerri Wright

    British National Formulary
  Exercises
  Numeracy Information

Exercises

I have categorised the exercises here according to the sections in the book so you can go back and read explanations if you’ve forgotten how to do these. The exercises do gain in difficulty as you move down the list as some of the questions will depend on you knowing how to convert between units of measurement or calculate dosage per patient body weight for example.

The Answers can be downloaded from the end of every section.

Conversions
Dosages expressed as weight/units
Dosages per body weight/BSA
Divided dosages
Weight/volume dosages
Fluid replacement prescription
Hourly infusion prescriptions
Syringe drivers

Conversions

Exercise 1

Express 0.5g in milligrams
Express 1.8g in milligrams
Express 0.1g in milligrams
Express 2.5g in milligrams
Express 0.125g in milligrams
Express 0.25g in milligrams
Express 0.01g in milligrams
Express 1.24g in milligrams
Express 1.2g in milligrams
Express 0.8g in milligrams

Exercise 2

Express 0.1mg in micrograms
Express 10mg in micrograms
Express 0.6mg in micrograms
Express 0.24mg in micrograms
Express 0.002 mg in micrograms
Express 1.6mg in micrograms
Express 0.076mg in micrograms
Express 0.56mg in micrograms
Express 1.28mg in micrograms
Express 0.8mg in micrograms

Exercise 3

Express 500mg in grams
Express 1600mg in grams
Express 1000mg in grams
Express 100mg in grams
Express 125mg in grams
Express 250mg in grams
Express 750mg in grams
Express 50mg in grams
Express 2500mg in grams
Express 800mg in grams

Exercise 4

Express 750mcg in milligrams
Express 500mcg in milligrams
Express 1200 mcg as milligrams
Express 100mcg as milligrams
Express 80mcg as milligrams
Express 3000 mcg as milligrams
Express 400mcg as milligrams
Express 50mcg as milligrams
Express 20 000mcg as milligrams
Express 2500mcg as milligrams

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Dosages expressed as weight/unit

Exercise 1

Your patient has been prescribed 500mg flucloxacillin. The tables available are 250mg. How many tablets would you administer?
You need to administer 30mg prednisolone to your patient. The tablets available at 5mg. How many tablets do you need to administer to make this dose?
The prescription is for 1g paracetamol. The tablets available are 500mg. How many tablets do you need to administer?
Your patient has been prescribed 1.2g benzylpenicillin. The vials available are 600mg. How many vials do you need to administer?
You need to administer 0.6mg hysocine bromide. The ampoules available are 400mcg. How many ampoules do you need to administer?

Exercise 2

?You need to administer citrolopram 40mg to your patient. The tablets available are 20mg. How many tablets do you need to administer?
Your patient needs to take 200mcg salbutamol four times a day. The inhaler releases 100mcg with each ‘puff’. How many ‘puffs’ does your patient need to take?
You have a 10ml ampoule of adrenaline strength 1:10 000. How many milligrams of adrenaline does this ampoule contain?
You need to administer 6000 units of clexane. The pre filled injection available contains 10 000 units/ml. How many millilitres would you administer?
Your patient has been prescribed 250mcg digoxin. The tablets available are 62.5mcg. how many would you administer?

Exercise 3

?You need to add 15 mmols potassium to an intravenous infusion. The ampoules of potassium available are 10mls of strength 2mmol/ml. How many millilitres of this ampoule would you administer?
Your patient has been prescribed 720mcg desmopressin in 3 divided dosages daily sublingually. The tablets available are 120mcg and 240mcg strength. How many of which strength do you need to administer?
Your patient has been prescribed 500mcg glucagon IM. The prefilled syringe contains 1mg. How much of the syringe would you administer?
You need to administer 4mg adrenaline. The adrenaline strength available is 1ml ampoules of 1:1000 adrenaline. How many ampoules do you need to administer?
You need to administer 20mg prednisolone. The tablets available are 5mg. How many tablets do you need to administer?

Exercise 4

?Your patient has been prescribed 1.5g tolbutamide in 3 divided dosages. The tablets available are 500mg. How many tablets would you administer for each dose?
You need to administer gliclazide 160mg daily. The tablets available are 80mg. How many tablets would you administer?
You need to administer 100mcg adrenaline. The ampoule available is a 1 ml ampoule of adrenaline 1:10 000 strength. How many millilitres would you administer?
Aspirin 900mg has been prescribed. The tablets available are 300mg strength. How many tablets would you need to administer?
You need to prepare an infusion containing 75 000 units heparin. The heparin ampoules available in stock are 25 000units/ml and 50 000units/ml. How many of which ampoule would you use for this infusion?

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Dosages per body weight/BSA

Exercise 1

Your patient has been prescribed 500mg flucloxacillin. The tables available are 250mg. How many tablets would you administer?
You need to administer 30mg prednisolone to your patient. The tablets available at 5mg. How many tablets do you need to administer to make this dose?
The prescription is for 1g paracetamol. The tablets available are 500mg. How many tablets do you need to administer?
Your patient has been prescribed 1.2g benzylpenicillin. The vials available are 600mg. How many vials do you need to administer?
You need to administer 0.6mg hysocine bromide. The ampoules available are 400mcg. How many ampoules do you need to administer?

Exercise 2

You need to administer citrolopram 40mg to your patient. The tablets available are 20mg. How many tablets do you need to administer?
Your patient needs to take 200mcg salbutamol four times a day. The inhaler releases 100mcg with each ‘puff’. How many ‘puffs’ does your patient need to take?
You have a 10ml ampoule of adrenaline strength 1:10 000. How many milligrams of adrenaline does this ampoule contain?
You need to administer 6000 units of clexane. The pre filled injection available contains 10 000 units/ml. How many millilitres would you administer?
Your patient has been prescribed 250mcg digoxin. The tablets available are 62.5mcg. How many would you administer?

Exercise 3

You need to add 15 mmols potassium to an intravenous infusion. The ampoules of potassium available are 10mls of strength 2mmol/ml. How many millilitres of this ampoule would you administer?
Your patient has been prescribed 720mcg desmopressin in 3 divided dosages daily sublingually. The tablets available are 120mcg and 240mcg strength. How many of which strength do you need to administer?
Your patient has been prescribed 500mcg glucagon IM. The prefilled syringe contains 1mg. How much of the syringe would you administer?
You need to administer 4mg adrenaline. The adrenaline strength available is 1ml ampoules of 1:1000 adrenaline. How many ampoules do you need to administer?
You need to administer 20mg prednisolone. The tablets available are 5mg. How many tablets do you need to administer?

Exercise 4

Your patient has been prescribed 1.5g tolbutamide in 3 divided dosages. The tablets available are 500mg. How many tablets would you administer for each dose?
You need to administer gliclazide 160mg daily. The tablets available are 80mg. How many tablets would you administer?
You need to administer 100mcg adrenaline. The ampoule available is a 1 ml ampoule of adrenaline 1:10 000 strength. How many millilitres would you administer?
Aspirin 900mg has been prescribed. The tablets available are 300mg strength. How many tablets would you need to administer?
You need to prepare an infusion containing 75 000 units heparin. The heparin ampoules available in stock are 25 000units/ml and 50 000units/ml. How many of which ampoule would you use for this infusion?

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Divided dosages

Exercise 1

Your patient requires Cefuroxime 500mg in two divided dosages daily. How many milligrams of cefuroxime would you administer for each dose?
You need to administer 800mg C-careldopa in four divided dosages daily. How many milligrams do you need to administer for each dose?
Your patient requires oxytetracycline 2g in four divided dosages daily. How many milligrams does your patient need each administration?
You need to administer Co-amoxiclav 750mg on three divided dosages daily. How many milligrams would you administer each dose?
Your patient requires 1.5g cetazidime in three divided dosages daily. What dosage would you give at each administration time? Answers

Exercise 2

Your patient has been prescribed 100mcg/Kg benzypenicillin in 4 divided doses. You patient weighs 6kg. How many milligrams of benzypenicillin does your patient need each dose.
You need to administer 1.2g carbemazepine in two divided doses. How many milligrams does your patient need each dose?
Your patient needs 8mg/Kg oxcabazepine daily in 2 divided dosages. If your patient weighs 15kg how many milligrams do you need to administer for each dose?
You need to administer 60mg/kg cefuroxime in 4 divided dosages. Your patient’s weight is 6kg. How many milligrams of cefuroxime do you need to administer for each dose?
Your patient has been prescribed 1.2g of a drug in 3 divided dosages. How many milligrams do they need to take of their drug at each administration time?

Exercise 3

You need to administer 400mg pivmecillinam hydrochloride to your patient in 4 divided doses. How many milligrams do you need to administer each dose?
The prescription for your patient is for 240mg Cefuroxime in four divided dosages. How many milligrams do you need to administer each dose?
You need to administer 360mg aztreonam IV to your patient in three divided doses. How many milligrams do you need to administer each dose?
Your patient has been prescribed 150mg diclofenac sodium in three divided dosages. How many milligrams do they require each dose
You need to administer 12mg diazepam in six divided doses. How many milligrams are required for each dose?

Exercise 4

You need to administer Cimetidine 30mg/Kg daily in 3 divided dosages. Your patient weighs 12kg. How many milligrams of cimetidine does your patient require for each dose?
Your patient has been prescribed Uniphyllin Continus 9mg/kg in 12 hour dosages. Your patient weighs 28kg. The maximum dosage for this drug is 800mg daily. Is this prescription dosage within this maximum dosage?
Your patient has a prescription for Methyphenidate Hydrochloride 1.4mg/Kg daily in two divided dosages. Your patient weighs 20kg. What dosage do they require at each administration?
A drug has been prescribed as 1.2mg daily in 4 divided dosages. Calculate the number of milligrams required at each administration time.
Your patient has been prescribed 120mcg/Kg of a drug daily in four divided dosage. Your patient weighs 22kg. How many milligrams do you need to administer for each dose?

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Weight/volume dosages

Exercise 1

You need to administer 6.25mg fluphenazine decanoate IM to your patient. The ampoules available are 25mg/ml. How many millilitres do you need to administer?
Your patient has been prescribed 10mg diazepam. The oral solution available contains 5mg/5ml. How many millilitres do you need to administer?
You need to give codeine phosphate 15mg to your patient. The oral solution available contains 3mg/5ml. How many millilitres do you need to administer?
You need to administer 0.5mg adrenaline to your patient. The ampoule available contains adrenaline strength 1:1000 in 1ml. How many millilitres do you need to administer?
30mg domperidone has been prescribed orally. The oral solution available contains 5mg/5ml. How many millilitres would you administer?

Exercise 2

You need to administer metoclopramide hydrochloride 500mcg to your patient IM. The ampoules available are 5mg/ml. How many millilitres would you administer?
Your patient has been prescribed paracetamol 500mg. The oral solution available contains 250mg/5ml. How many millilitres would you administer?
Your patient has been prescribed Lacosamide 150mg. The syrup available contains 15mg/ml. How many millilitres do you need to administer?
You need to administer 300mcg/kg diazepam rectally. Your patient weighs 3Kg and the rectal solution strength is 2mg/ml. How many millilitres of a 2.5mg/1.25ml tube do you need to administer?
Your patient has been prescribed midazolam 7.5mg. The solution available contains 10mg/ml. How many millilitres do you need to administer?

Exercise 3

Your patient has been prescribed 150mg orphenadrine hydrochloride. The oral solution strength is 25mg/5ml. How many millilitres do you need to administer?
You need to prepare an IV injection of sotalol hydrochloride 60mg. The ampoules available contain 10mg/ml. How many ampoules do you need to prepare?
Your patient has been prescribed 150mcg/kg atenolol. Your patient weights 65kg. The injection ampoules contain 500mcg/ml and are manufactured in 10ml ampoules. How many millilitres do you need to administer?
You need to administer benzylpenicillin 600mg orally. The oral solution strength contains 125mg/5ml. How many millilitres do you need to administer?
Ampillicin 1g has been prescribed. The oral solution available contains 250mg/5ml. How many millilitres do you need to administer?

Exercise 4

Your patient has been prescribed 250mg flucloxacillin. The oral solution contains 125mg/5ml. How many millilitres do you need to administer?
You need to administer 7.5mg/Kg clarithromycin. Your patient weighs 6kg and the oral solution contains 125mg/5ml. Calculate how many millilitres to administer?
You need to administer azathioprine 2mg/kg IV to a patient weighing 24kg. The ampoule available contains 50mg and is reconstituted with 10ml water for injection. How many millilitres would you need to draw up to prepare this infusion?
Gentamicin has been prescribed 4mg/Kg for your patient who weighs 38kg. The ampoules available contain 40mg/ml. How many millilitres would you administer?
Your patient has been prescribed promathazine hydrochloride 7.5mg. The elixir available contains 5mg/5ml. How many millilitres would you administer?

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Fluid replacement prescription

Exercise 1

For the following IV prescription chart calculate the rate per hour of each of the infusions.

Sunnydene and Reynold NHS Trust

Intravenous prescription chart

Name: Fred Kumar Hospital Number: 0789655 Consultant: Rogers

Date of Birth: 1/9/1952 Ward: Oak

Question number	Date prescribed	Solution	Volume	Duration of Infusion	Date to be given	Prescriber’s signature
1	1/8/2011	0.9% sodium chloride	1000ml	8 hours	1/8/2011	RDickenson
2	1/8/2011	Blood	1 unit (500ml)	4 hours	2/8/2011	R Dickenson
3	1/8/2011	5% dextrose	1000ml	10 hours	2/8/2011	RDickenson
4	1/8/2011	4% glucose, 0.18% sodium chloride (dextrose saline)	500ml	8 hours	3/8/2011	RDickenson
5	2/8/2011	0.9% sodium chloride	1000ml	12	3/8/2011	RDickenson

Exercise 2

For the following IV prescription chart calculate the drips per minute of each of the infusions using a manual giving set of drop factor 20 drops/ml. n.b the blood giving set has a drop factor of 15 drops/ml.

Sunnydene and Reynold NHS Trust

Intravenous prescription chart

Name: Fred Kumar Hospital Number: 0789655 Consultant: Rogers

Date of Birth: 1/9/1952 Ward: Oak

Question number	Date prescribed	Solution	Volume	Duration of Infusion	Date to be given	Prescriber’s signature
1	1/8/2011	0.9% sodium chloride	1000ml	8 hours	1/8/2011	RDickenson
2	1/8/2011	Blood	1 unit (500ml)	4 hours	2/8/2011	R Dickenson
3	1/8/2011	5% dextrose	1000ml	10 hours	2/8/2011	RDickenson
4	1/8/2011	4% glucose, 0.18% sodium chloride (dextrose saline)	500ml	8 hours	3/8/2011	RDickenson
5	2/8/2011	0.9% sodium chloride	1000ml	12	3/8/2011	RDickenson

Exercise 3

Your patient has been prescribed 1000ml 0.9% sodium chloride over 10 hours. Using a manual giving with a drop factor of 20 drops/ml
You need to programme a volumetric device with the rate per hour for a 500ml infusion running over 4 hours. What rate per hour would you set this devise for?
You need to set up an infusion over 12 hours of 5% dextrose 1000ml using a manual giving set with a drop factor of 15 drops/ml. How many drops per minute would you set this infusion for?
You need to give a unit of blood (500ml) over 6 hours using a volumetric pump. What rate would you set this for (rate/hr)?
An infusion of 10% dextrose 500ml has just finished infusing into a patient. How many grams of glucose have they received?

Exercise 4

You have been asked to set up an intravenous infusion of 5% glucose 500ml for your patient over 6 hours. You set this up at 10am. What time is it due to finish?
Using the infusion details above what rate per hour would you set this infusion for using a volumetric devise?
Your patient has just been prescribed 1000ml 0.9% sodium chloride over 12 hours. Using a manual giving set with drop factors 20 drops/ml how many drips per minute would you set this for?
How many grams of sodium chloride are there in a 1000ml 0.9% infusion bag?
Your colleague sets an infusion up of 500ml dextrose saline to run over 8 hours for a patient. The volumetric device is set for 83ml/hr. Is this correct?

Exercise 5

You have been asked to set up an intravenous infusion of 5% glucose 500ml for your patient over 4 hours. You set this up at 04:00hrs. What time is it due to finish?
Your patient has just been prescribed 1000ml 0.9% sodium chloride over 10 hours. Using a manual giving set with drop factors 20 drops/ml how many drips per minute would you set this for?
Your colleague sets an infusion up of 1000ml 0.9% sodium chloride to run over 12 hours for a patient. The volumetric device is set for 83ml/hr. Is this correct?
Your patient requires an infusion of 500ml hartmanns solution to run over 2 hours. Using a volumetric device what rate per hour would you set this for?
How many grams glucose and sodium chloride are contains in a 500ml infusion bag of dextrose saline (4% glucose and 0.18%sodium chloride)

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Hourly infusion prescriptions

Exercise 1

Your patient needs to be administered 0.2 mcg/Kg/Min of a drug. Your patient’s weight is 35 Kg. The infusion used in your area is 12mg/50ml. Calculate the rate per hour you would set this infusion up for?
Your patient has an infusion of heparin 50 000units running at 2mls/hour. How many units is your patient receiving of heparin? N.b the infusion is 50ml.
You need to administer 1mcg/Kg/Min of a drug. The infusion available is 800mg/500ml and your patient weights 30Kg. How many millilitres per hour would you set this infusion for?
You set up an infusion of dopamine containing 80mg/50ml and set the rate as 2ml/hr. How many milligrams of the drug is the patient receiving per hour?
The prescription for your patient is 4mcg/Kg/Min of a drug. Your patient weighs 48Kg and the standard infusion for your area is 200mg/50ml. What rate would you set this infusion for?

Exercise 2

Your patient has been prescribed 0.08mcg/Kg/Min of a drug. The patient weighs 45Kg and the infusion used in your unit is 4mg/50ml. What rate per hour would you set this infusion up for?
The prescription for your patient is 5mcg/Kg/Min of a drug. Your patient weighs 78Kg and the standard infusion for your area is 200mg/50ml. What rate would you set this infusion for?
Your patient has been prescribed heparin 15 000units over 24 hours. The ampoules available are 25 000units/ml. How many millilitres would you draw up and what rate would you set this infusion for to administer 1000units/hour
Your patient needs to be administered 0.3 mcg/Kg/Min of a drug. Your patient’s weight is 52 Kg. The infusion used in your area is 12mg/50ml. Calculate the rate per hour you would set this infusion up for?
Your patient has been prescribed 50units actrapid/50ml and requires 6 units per hour administered initially. What rate would you set this infusion for?

Exercise 3

The prescription for your patient is 4mcg/Kg/Min of a drug. Your patient weighs 44Kg and the standard infusion for your area is 200mg/50ml. What rate would you set this infusion for?
Your patient needs to be administered 0.2 mcg/Kg/Min of a drug. Your patient’s weight is 38 Kg. The infusion used in your area is 12mg/50ml. Calculate the rate per hour you would set this infusion up for?
Your patient has been prescribed 0.06mcg/Kg/Min of a drug. The patient weighs 52Kg and the infusion used in your unit is 4mg/50ml. What rate per hour would you set this infusion up for?
Your patient has been prescribed 50units actrapid/50ml and requires 2 units per hour administered initially. What rate would you set this infusion for?
You need to administer 30 000units heparin as a continuous infusion over 24 hours. The ampoules available are 50 000units/ml. How many millilitres do you need to draw up? What rate do you need to set this infusion for to administer 1800 units/hour?

Exercise 4

Your patient has been prescribed 50units actrapid/50ml and requires 8 units per hour administered initially. What rate would you set this infusion for?
Your patient has an infusion of heparin 75 000units running at 3mls/hour. How many units is your patient receiving of heparin? N.b the infusion is 50ml.
You need to administer 0.5mcg/Kg/Min of a drug. The infusion available is 800mg/500ml and your patient weights 42Kg. How many millilitres per hour would you set this infusion for?
You set up an infusion of dopamine containing 80mg/50ml and set the rate as 4ml/hr. How many milligrams of the drug is the patient receiving per hour?
You need to administer 2mcg/kg/min to your patient who weighs 32kg. The standard infusion rate for your area is 80mg/50ml. How many millilitres per hour would you set this infusion for?

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