Introduction to Medication Calculations

Introduction to
Medication
Calculations for
Nursing Students

Please Click Slide to Proceed

Objectives

► Gain an understanding of the formulas
used to calculate correct medication for
administration.
► Show examples of medication formulas
and calculations.
► Practice questions throughout the
presentation with a test at the end.


Test Your Current Knowledge
1. A
patient is ordered an injection of 80mg of Pethidine. Each stock
ampoule 100mg per 1ml. How much will you draw up?

3. Apatient is prescribed 3g of Sulphadiazine, the stock contains
600mg/5ml. How much Sulphadiazine should be given to the patient?

5. A
patient is prescribed 1L of a Saline solution. The rate is set at 100ml/hr.
How long will the infusion take?

7. How many 300mg tablets are required for a prescribed dose of 450mg?

9. Adoctor orders Penicillin via Potassium oral suspension 56mg/kg/day in
four doses per day for a child who weighs 25kg. The suspension
available is 125mg/5ml. What volume should be administered at each
dose?

Please Click Slide to Proceed when ready

Answers
1. .8ml
2. 25ml
3. 10 hours
4. 1.5 Tablets
5. 350mg


Medication Formulas –
Tablets

Strength Required Number Of
= Tablets
Stock Strength

MEANS DIVIDE
THE TOP
NUMBER BY THE
BOTTOM

Tablets

Medication Example:
750mg CIPROFLOXACIN IS ORDERED ON HAND
ARE 500mg TABLETS. HOW MANY TABLETS SHOULD BE
GIVEN?

Stock Strength = Tablets
750mg
500mg = 1.5 TABLETS


Tablets

Medication Example :
HOW MANY 20mg TABLETS OF CODEINE ARE REQUIRED
FOR A DOSE OF 0.05g?

Stock Strength
= Tablets
Requires Conversion

g to mg – 0.05g x 1000 = 0.05 x 1000 = 50mg

50mg

20mg
= 2.5 TABLETS

Volume / Injection

Strength Required
Volume
Stock Strength
X Volume = Required

Volume in the Ampoule

Volume / Injection
Volume Medication Example:
CALCULATE THE VOLUME TO BE DRAWN UP IF A
PATIENT REQUIRES 1 mg OF BUMETANIDE, AND EACH
STOCK AMPOULE CONTAINS 2mg/4ml
Volume Formula Calculation

Strength Required
Volume To Be
Stock Strength
X Volume = Administered
1mg
X 4ml = 2 ml
2mg


Volume / Injection
AN INFANT REQUIRES 2000 units OF CALCIPARINE. IF
STOCK AMPOULES CONTAIN 20000 units in 1 ml . HOW
MUCH SHOULD YOU DRAW UP?


Strength Required Volume To Be
Stock Strength

2000 units

20000 units
X 1ml = .1 ml

Volume / Injection
IF AN ADULT PATIENT WAS ORDERED 85mg OF
CORTISONE, AND EACH STOCK AMPOULE WAS 5 ml
AND CONTAINED 100mg OF CORTISONE, FIND THE
VOLUME REQUIRED?
Volume To Be
Strength Required X Volume = Administered
Stock Strength

85mg X 5ml = 4.25 ml
100mg

Volume / Injection
A PATIENT ORDERED 70mg OF PETHIDINE, FIND
THE VOLUME REQUIRED IF THE STOCK SOLUTION
CONTAINS 10g OF PETHIDINE PER 200ml?

Strength Required Volume To Be
Stock Strength

Conversion Required

g to mg – 10g x 1000 = 10000mg
70 mg
X 200ml = 1.4 ml
10000 mg

Tablet and Volume Quiz
Strength Required Number Strength Required
= Of
Stock Strength
X Volume
Stock Strength Tablets

1. The patient is ordered Amisulpride Tablets. Order is 1200mg Mane, the
tablets come in 400mg. How many tablets do you administer?
2. The patient ordered Coversyl Plus 2.5mg Mane. Coversyl comes in
5mg Tablets. How many tablets do you give?
3. A patient experiencing pain is ordered 25mg of Toradol (Ketorolac
Trometamol). The Toradol comes in 30mg/1ml. How many mls do you
draw up?
4. A 2 year old child is ordered Painstop (120mg Paracetamol/Codeine
Phosphate 5mg/5ml). The child is ordered 5ml Painstop every 6 – 8
Hours. How many mls do you administer?
5. A patient has returned from theatre with Nausea. The PRN order is for
Ondansetron IMI. The order is for 6mg, the Ondansetron comes in 4mg/
2ml. How many mls do you draw up?


Tablet and Volume Answers
1.The patient
is ordered Amisulpride Tablets. Order is 1200mg
OD, the tablets come in 400mg. How many tablets do you
administer?
1200mg
= 3 Tablets
400mg

5.The patient
ordered Coversyl Plus 2.5mg Mane. Coversyl
comes in 5mg Tablets. How many tablets do you give?

5mg
= /2 Tablet
1
2.5mg


1.Apatient experiencing pain is ordered 25mg of Toradol (Ketorolac
Trometamol). The Toradol comes in 30mg/1ml. How many mls do you
draw up?
25mg
X 1ml = 0.8ml

30mg

6.A
2 year old child is ordered Painstop (120mg Paracetamol/Codeine
Phosphate 5mg/5ml). The child is ordered 5ml Painstop every 6 – 8 Hours.
How many mls do you administer?

5ml



4.A
patient has returned from theatre with Nausea. The PRN order is for
Ondansetron IMI. The order is for 6mg, the Ondansetron comes in
4mg/2ml. How many mls do you draw up?

6mg
X 2ml = 3ml
4mg


Medication Formulas – Weight
Weight Calculation

mg for each Kg

Example: Child weighs 48kg the dose is 16mg for
each Kg.

16mg x 48kg = 768mg/Kg required

Use formula to complete how much you need.


Weight
Medication Example:

A 5 YEAR OLD GIRL IS ORDERED PARACETAMOL STAT. THE
PHARMACY GUIDELINES RECOMMEND 15mg/Kg . THE CHILD WEIGHS
18Kg . STOCK IS 125mg/5ml. HOW MANY mls WILL THE CHILD RECEIVE ?
WEIGHT CALCULATION

15mg for each Kg – 15 x 18 = 270mg


Volume To Be
=
Strength Required
X Volume Administered
Stock Strength

270mg

125mg
X 5ml = 10.8 ml


Medication Formulas – Weight
Medication Example:
A CHILD WEIGHING 16kg IS ORDERED 40mg/Kg/Day. 4 DOSES A DAY , OF
ERYTHROMYCIN. FIND THE STRENGTH FOR A SINGLE DOSE ?

Weight Calculation

40mg For Each Kg – 40 X 16 = 640mg/Day

New Calculation Formula

Strength Required Per Day
= Single Dose Per Day
Number Of Doses Per Day

640mg

4 doses
= 160mg for each single dose


Medication Formulas – IV Infusions

Volume
Flow Rate =
Time

Volume of fluid
being
administered Time for volume
to be infused


Medication Formulas – IV Infusions
IV Infusion Calculation Example

A PATIENT REQUIRES 1000ml FLUID OVER 8 HOURS. FIND THE FLOW
RATE?
IV Infusion Calculation

Volume
Flow Rate =
Time
1000mls
= 125mls/hr
8hr

Medication Formulas – Iv Infusions

IV Infusion Calculation Example

A PATIENT IS TO RECEIVE 600ml 5% DEXTROSE IN WATER IV TO BE
INFUSED OVER 4 HOURS. CALCULATE THE RATE IN mls/h TO BE
DELIVERED BY PUMP?

IV Infusion Calculation
Volume
Flow Rate =
Time
600mls
= 150mls/hr
4hr

Weight and IV fluid Administration Quiz
Volume
mg x Kg Flow Rate = Time
1. Calculate the size of a single dose if a child weighing 20
kg is ordered Flucioxacillin 100mg/kg/day. 4 doses per
day?
2. Calculate the flow rate if 1.2L is to be infused over 24
hours?
3. A 5 Year Old Girl is ordered paracetamol stat. The
pharmacy guidelines recommend 15mg/Kg. The child
weighs 25Kg. Stock is 125mg/5ml. How many ml will the
child receive?
4. A 1000ml bag of Hartman's is to be infused over 18hours.
What is the flow rate?
5. A patient is ordered antibiotics. A 100mg of Metronidazol
in a 100ml. It is to be infused over an hour how what is the
flow rate?

Weight and IV fluid Administration Answers

1.Calculate the size of a single dose if a child weighing 20 kg is ordered
Flucioxacillin 100mg/kg/day. 4 doses per day?

Weight Calculation: 20kg x 100mg = 2000

2000
4 doses
= 500mg for each single dose

8.Calculate the flow rate if 1.2L is to be infused over 24 hours?

Conversion: Litres to mls – 1.2 x 1000 = 1200mls

1200 = 50 mls/hr
24 Hours


•A 5 Year Old Girl is ordered paracetamol stat. The pharmacy
guidelines recommend 15mg/Kg. The child weighs 25Kg. Stock
is 125mg/5ml. How many ml will the child receive?
Weight Calculation: 25kg x 15mg = 375mg

375
X 5ml = 15ml
125

•A 1000ml bag of Hartman's is to be infused over 18hours. What
is the flow rate?

1000
18 Hours = 55.55* or 56 mls/hr



3.Apatient is ordered antibiotics. A 100mg of
Metronidazol in a 100ml. It is to be infused
over an hour how what is the flow rate?

100mg
= 100 mls/hr
100ml


Your Turn
1. A child requires 50 milligrams of Phenobarbitone. If stock
ampoules contain 200 mg in 2ml, how much will you draw
up?
2. What volume is required for the injection if a patient is
ordered 500mg of Capreomycin Sulphate, and each stock
ampoules contains 300mg/ml?
3. A patient needs 5000mg of medication. Stock solution
contains 1g per 1ml. What volume is required?
4. A teenager is prescribed 1000mg of Chloramphenicol, stock
on hand contains 250 mg/10ml in suspension. Calculate the
volume required?


Your Turn
1. How many 25mg tablets are required for a prescribed
dose of 0.05g?
2. Calculate the size of a single dose if a child weighing
15 kg is ordered Flucioxacillin 100mg/kg/day. 4 doses
per day.
3. 500ml is to infuse over 5 hour period. Find the flow
rate in ml/h?
4. A child weighing 45kg requires antibiotics which are
ordered 75mg/kg. How much will the child get in a
single day if there are 3 doses a day?


Your Turn
1. An adult is to be administered 500ml of blood in
3 hours. What is the mls/hr required to
administer in the required time?
2. A 100ml bag of Metronidazol is to be
administered over 30minutes. What is the mls/hr
to achieve this?


End of Tutorial
Congratulations you have completed the first part of the medications tutorial. Please
email you final answer to the following email address: Shane.King@usq.edu.au and
a result and certificate of completion will be emailed back. The certificate is
equivalent to .5 points towards your education requirements for the year.

Upcoming Medication Tutorials will include:

• Drip Rates

• Formula for amount of fluid has been infused

• Formula for the length of time of the infusion

• Formula to find out the time it will take to infuse fluid

• Patient Controlled Analgesia calculations

Introduction to Medication Calculations

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