DOSAGE CALCULATIONS

DesiredWhat is the desired

(ordered amount)?

DOSAGE CALCULATIONS

HaveWhat do you have

(amount on hand)?

DOSAGE CALCULATIONS

VehicleHow is the dosage measured

(quantity)?

DOSAGE CALCULATIONS

D

HV

Desired over Have times Vehicle

DOSAGE CALCULATIONS

Desired over Have times Vehicle

The order readsLasix 20 mg po

You haveLasix 20 mg tablets

How many tablets will you give?

DOSAGE CALCULATIONS

20 mg1 tablet

Desired over Have times Vehicle

20 mg

DOSAGE CALCULATIONS

20 mg1 tablet

The labels of Desired and Have MUST match

20 mg

DOSAGE CALCULATIONS

20 mg1 tablet

20 mg

If the labels match, then they cancel each other out

DOSAGE CALCULATIONS

201 tablet

20

Reduce the fraction if possible

DOSAGE CALCULATIONS

11 tablet

1

Do the multiplication

DOSAGE CALCULATIONS

1 1 tablet = 1 tablet

Calculate the Dosage

DOSAGE CALCULATIONS

Give 1 tablet

Amount to Give

DOSAGE CALCULATIONS

Desired over Have times Vehicle

The order readsLasix 30 mg po

You haveLasix 20 mg tablets

How many tablets will you give?

DOSAGE CALCULATIONS

30 mg1 tablet

Desired over Have times Vehicle

20 mg

DOSAGE CALCULATIONS

30 mg1 tablet

The labels of Desired and Have MUST match

20 mg

DOSAGE CALCULATIONS

30 mg1 tablet

If the labels match, then they cancel each other out

20 mg

DOSAGE CALCULATIONS

301 tablet

20

Reduce the fraction if possible

DOSAGE CALCULATIONS

31 tablet

2

Do the multiplication

DOSAGE CALCULATIONS

11 tablet

21

Calculate the Dosage

DOSAGE CALCULATIONS

Give 1

Amount to Give

1

2Tablets

DOSAGE CALCULATIONS

Desired over Have times Vehicle

The order readsDilantin Suspension 200 mg po

You haveDilantin Suspension 125 mg / 5 mL

How many mL will you give?

DOSAGE CALCULATIONS

200 mg5 mL

Desired over Have times Vehicle

125 mg

DOSAGE CALCULATIONS

200 mg

The labels of Desired and Have MUST match

125 mg5 mL

DOSAGE CALCULATIONS

If the labels match, then they cancel each other out

200 mg

125 mg5 mL

DOSAGE CALCULATIONS

200

1255 mL

Reduce the fraction if possible

DOSAGE CALCULATIONS

5 mL

Do the multiplication

8

5

DOSAGE CALCULATIONS

8

11 mL

Calculate the Dosage

DOSAGE CALCULATIONS

Give 8 mL

Amount to Give

DOSAGE CALCULATIONS

Does the dosage need to be converted?

The order readsMorphine Sulfate gr ¼ sc

You haveMorphine Sulfate 10 mg / 1 mL

How many mL will you give?

DOSAGE CALCULATIONS

Caution: The labels MUST match!

The order readsMorphine Sulfate gr ¼ sc

You haveMorphine Sulfate 10 mg / 1 mL

How many mL will you give?

CONVERSIONS

Converting Between the Systems

Weight

60 mg = gr i

The Metric System and the Apothecary System

CONVERSIONS

Setting Up the Proportion

Step 1: What DO you know?

60 mg = 1 gr

This is the first part of your proportion

60 mg : 1 gr :: 45 mg : x gr

CONVERSIONS

Setting Up the Proportion

Step 1: What DO you know?

60 mg = 1 gr

This is the first part of your proportion

60 mg : 1 gr :: 45 mg : x gr

CONVERSIONS

Setting Up the Proportion

Step 2: What do you WANT to know?

x mg = gr ¼

This is the second part of your proportion

60 mg : 1 gr :: x mg : ¼ gr

CONVERSIONS

Checking the Proportion

Step 3: Are the labels in the same order?

60 mg : 1 gr :: x mg : ¼ gr

mg : gr mg : gr

Caution: Changing the order of the labels

will yield the WRONG ANSWER

CONVERSIONS

Step 4: Solve the proportion

60 mg : 1 gr :: x mg : ¼ gr

x = 60 ¼

60 4

x =

x = 15 mg

Caution: Don’t forget to LABEL your answer

CONVERSIONS

Step 4: Solve the proportion

60 mg : 1 gr :: x mg : ¼ gr

x = 60 ¼

60 4

x =

x = 15 mg

Caution: Do you have the RIGHT label?

DOSAGE CALCULATIONS

Look back at the order

The order readsMorphine Sulfate gr ¼ sc

You now knowgr ¼ = 15 mg

You can convert this order toMorphine Sulfate 15 mg sc

DOSAGE CALCULATIONS

Now use Desired over Have times Vehicle

The order isMorphine Sulfate 15 mg sc

You haveMorphine Sulfate 10 mg / 1 mL

How many mL will you give?

DOSAGE CALCULATIONS

15 mg1 mL

Desired over Have times Vehicle

10 mg

DOSAGE CALCULATIONS

15 mg

The labels of Desired and Have MUST match

10 mg1 mL

DOSAGE CALCULATIONS

If the labels match, then they cancel each other out

15 mg

10 mg1 mL

DOSAGE CALCULATIONS

15

101 mL

Reduce the fraction if possible

DOSAGE CALCULATIONS

3= 1.5

2

Remember: The metric system uses decimals

DOSAGE CALCULATIONS

1.5 1 mL

Do the multiplication and calculate the dosage

DOSAGE CALCULATIONS

Give 1.5 mL

Amount to Give

DOSAGE CALCULATIONS

Look back to the original order

The order is

Morphine Sulfate 15 mg sc

You have

Morphine Sulfate 10 mg / 1 mL

You will give

1.5 mL Morphine Sulfate

DOSAGE CALCULATIONS

You can also use the Proportion Method

The order isMorphine Sulfate 15 mg sc

You haveMorphine Sulfate 10 mg / 1 mL

How many mL will you give?

Using the Proportion Method

Step 1: What do you Have (Label)?

Morphine Sulfate 10 mg / 1 mL

This is the first part of your proportion

10 mg : 1 mL :: 45 mg : x gr

DOSAGE CALCULATIONS

Using the Proportion Method

Step 2: What do you Desire (Order)?

Morphine Sulfate 15 mg

This is the second part of your proportion

10 mg : 1 mL :: 15 mg : x mL

DOSAGE CALCULATIONS

Using the Proportion Method

Step 3: Are the labels in the same order?

10 mg : 1 mL :: 15 mg : x mL

mg : gr mg : gr

Caution: Changing the order of the labels

will yield the WRONG ANSWER

DOSAGE CALCULATIONS

Step 4: Solve the proportion

10 mg : 1 mL :: 15 mg : x mL

15 = 10x

1510

= x

x =

Caution: Don’t forget to LABEL your answer

DOSAGE CALCULATIONS

1.5 mL

Step 4: Solve the proportion

10 mg : 1 mL :: 15 mg : x mL

15 = 10x

1510

= x

x =

Caution: Do you have the RIGHT label?

DOSAGE CALCULATIONS

1.5 mL

DOSAGE CALCULATIONS

Look back to the original order

The order is

Morphine Sulfate 15 mg sc

You have

Morphine Sulfate 10 mg / 1 mL

You will give

1.5 mL Morphine Sulfate

DOSAGE CALCULATIONS

Calculate this dose using the D/H * V Method

The order readsDilantin Suspension 400 mg po

You haveDilantin Suspension 125 mg / 5 mL

How many mL will you give?

DOSAGE CALCULATIONS

Calculate this dose using the Proportion Method

The order readsDilantin Suspension 400 mg po

You haveDilantin Suspension 125 mg / 5 mL

How many mL will you give?

Desired over Have times Vehicle

– or –

Set up a Proportion

DOSAGE CALCULATIONS

It’s really YOUR Choice