Medical Dosage Calculation Copyright ©2012, ©2008 by Pearson Education, Inc. All rights reserved. Medical Dosage Calculations: A Dimensional Analysis Approach,

Medical Dosage CalculationMedical Dosage Calculation

Copyright ©2012, ©2008 by Pearson Education, Inc.All rights reserved.

Medical Dosage Calculations: A Dimensional Analysis Approach, Tenth EditionJune L. Olsen • Anthony P. Giangrasso • Dolores Shrimpton

CHAPTER

Tenth EditionA Dimensional Analysis ApproachA Dimensional Analysis Approach

Preparation of Solutions

8



Directory

• Classroom Response System Questions• Lecture Note Presentation



Classroom Response System Questions



Question #1

If a 25% solution is diluted, what might be the strength of the resulting solution?



Question #1 Choices

1. 50%

2. 25%

3. 10%

4. 75%



Question #1 Response

1. 50%

2. 25%

3. 10%

4. 75%



Question #2

If a 1:69 solution is diluted, what might be the strength of the resulting solution?



Question #2 Choices

1. 1:30

2. 1:90

3. 2:120

4. 3:12




1. 1:30

2. 1:90

3. 2:120

4. 3:12



Question #3

If 1 liter of a solution contains 100 grams of pure drug, what is the strength of this solution as a fraction, ratio, and as a percentage?



Question #3 Choices

1. 1/100 strength, 1:100, 1%

2. 1/1000 strength, 1:1000, 0.1%

3. ½ strength, 1:2, 50%

4. 1/10 strength, 1:10, 10%




1. 1/100 strength, 1:100, 1%

2. 1/1000 strength, 1:1000, 0.1%

3. ½ strength, 1:2, 50%

4. 1/10 strength, 1:10, 10%



Question #4

The strength stated on a drug label is 100 mg/mL. Write this strength in the form of a percentage.



Question #4 Choices

1. 500%

2. 50%

3. 5%

4. 10%




1. 500%

2. 50%

3. 5%

4. 10%



Question #5

The physician orders minoxidil (Rogaine) 2%; apply 2 mL to scalp b.i.d. How many milligrams of minoxidil will be applied to the scalp with each dose?



Question #5 Choices

1. 40 mg

2. 4 mg

3. 5 mg

4. 2 mg




1. 40 mg

2. 4 mg

3. 5 mg

4. 2 mg



Lecture Note Presentation



Learning Outcomes

1. Describe the strength of a solution as a ratio, fraction and as a percent.

2. Determine the amount of solute (drug) in a given amount of solution.

3. Determine the amount of solution that would contain a given amount of solute (drug).

4. Do the calculations necessary to prepare a solution from a solute.

5. Do the calculations necessary to prepare solutions for irrigations, soaks, and nutritional feedings.



Strength of a Solution

Examples of strength using stated units of measurement:

Strength =

Amount of Drug (Solute)

Amount of Solution

5 mg

mL,

25 mcg

5 mL, and

8 g

L



• Solution strength can also be stated without explicit units of measurement. For example, a solution which is 1 part iodine in 2 parts of solution has strength of:

Ratio

Fraction

Percent


1:2

50%

1

2strength



• Measure the Amount of Drug (Solute) in either g or mL

• Measure the Amount of the Solution in mL


1:100 NaCl solution has 1 g NaCl in 100 mL of the solution

1/3 strength solution of Iodine has 1 mL of Iodine in 3 mL of solution.

7% magnesium sulfate solution has7 g magnesium sulfate in 100 mL of solution



• What is the strength of a 500 milliliter solution that contains 50 mL of iodine?

strength =

amount of drugamount of solution

The strength is 1:10, 1/10 strength, or 10%

= 50 mL

500 mL

1

10

Find the Strength



• What is the strength of a 200 milliliter solution that contains 50 g of NaCl?

strength =

50g200mL

=14=25%

The strength is 1:4, ¼ strength, or 25%

=

50 g -------------200 mL

4

1

Find the Strength

strength =

amount of drugamount of solution



• How many grams of dextrose would you need to prepare 1000 milliliters of a 5% solution?

Amount of solution is 1,000 milliliters.

Strength is 5%

Find the amount of solute in a given amount of solution of known strength

5

100

⎛

⎝⎜⎞

⎠⎟

5 g

100 mLThis means



So, you need 50 grams of dextrose to prepare 1,000 milliliters of a 5% solution.

50 g

Convert 1,000 mL of solution to g of dextrose

1,000 mL ×

5 g100 mL

=? g



• How would you prepare 250 milliliters of a 1/2% creosol solution? Creosol comes in liquid form.

Amount of solution is 250 milliliters.

Finding the Amount of Solute

This means

Strength is ½% or 0.5%

0.5 g Creosol

100 mL Solution



0.5 g Creosol

100 mL Solution

So, 1.25 milliliters of creosol is diluted with water to 250 milliliters of solution.

=1.25 mL Creosol

Convert 250 mL solution to ? mL of Creosol

0.5 g Creosol

100 mL Solution=? mL of Creosol



You want to convert the 40 grams of pure drug to milliliters of solution.

40 g = ? mL

Find the amount of solution of known strength containing a given amount of solute

• How many milliliters of a 20% magnesium sulfate solution will contain 40 grams of the solute magnesium sulfate?



In a 20% solution, there are 20 grams of solute per 100 mL of solution. So, the strength is

1

2

200 mL

So, 200 mL of a 20% magnesium sulfate solution contains 40 g of magnesium sulfate.

20 g

100 mL

40 g

1×100 mL20 g

=? g



• How many ounces of full-strength Sustacal are needed to make 16 ounces of ¼ strength Sustacal?

Finding the Amount of Solute



= 4 oz

So, 4 oz of full-strength Sustical are needed to make 16 ounces of ¼ strength Sustical.

16 oz Solution = ? oz Sustical

= ? oz Sustical

1

4strength means

1 oz (Sustical)

4 oz (Solution)

16 oz Solution

1×1 oz (Sustical)4 oz (Solution)

16 oz Solution

1×1 oz (Sustical)4 oz (Solution)

1

4



Chapter Summary

• The strength of a solution is the ratio of the amount of solute dissolved in the solution to the total volume of the solution.

• The strength of a solution may be expressed in the form of a ratio,fraction,or percentage.

• A 1/2 strength solution is a 1:2 or a 50% solution, and should not be confused with a 1/2 % solution.



Chapter Summary

• The amount of solute dissolved in the solution should be expressed in milliliters if the solute is a liquid.

• The amount of solute dissolved in the solution should be expressed in grams if the solute is a solid or powder.

• The volume of a solution should be expressed in milliliters.



Chapter Summary

• To determine the amount of solute contained in a given amount of a solution of known strength, use the strength as the known equivalence.

• To determine amount of a solution of known strength containing a given amount of solute, use the strength as the known equivalence.



• The strength of a particular solution may be written in many different forms. The following strengths are all equivalent:

• With stated Units of Measurement

Rates500 mg/mL

500 mg per mL

500 mg

1 mL

Equivalence 500 mg = 1 mL

Chapter Summary

{



• Without stated Units of Measurement

Fraction 1/2 strength

Ratio 1:2

Percentage 50%

Chapter Summary

Documents

Medical Dosage Calculation Copyright ©2012, ©2008 by Pearson Education, Inc. All rights reserved. Medical Dosage Calculations: A Dimensional Analysis Approach,