Calculations of Percentage Strength of Weight-In-Volume (%W/V) – PST04105 Pharmaceutical Calculations

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NTA Level 4 • Semester 1 • PST04105

Calculations of Percentage Strength of Weight-In-Volume (%W/V)

Pharmaceutical Calculations • Source Session/Topic 13
Full source-text version: all educational wording from the extracted learning source is retained; only presenter/tutor metadata and web-layout noise are removed, while formatting is improved for readability.

Session 13: Calculations of Percentage Strength of Weight-In-Volume (%W/V)

Total Session Time: 120 minutes

Prerequisites

• None

Learning Tasks

By the end of this session students are expected to be able to:

• Define the percentage %W/V of a given product
• Calculate the amount of a product/active ingredient from a given

percentage %W/V

Resources Needed:

• Flip charts, marker pens, and masking tape
• Black/white board and chalk/whiteboard markers

SESSION OVERVIEW

|Step |Time |Activity/ |Content |

| | |Method | |

|1 |05 minutes |Presentation |Introduction, Learning Tasks |

|2 |25 minutes |Presentation |Definition of Percentage %W/V of a |

| | |Brainstorming |Given Product |

|3 |60 minutes |Presentation |Calculation of the Amount of a |

| | |Group |Product/Active Ingredient From a |

| | |discussion |Given Percentage %W/V |

|4 |15 minutes |Presentation |Key Points |

| 5 |15 minutes |Presentation |Evaluation |

SESSION CONTENTS

STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)

READ or ASK students to read the learning tasks and clarify

ASK students if they have any questions before continuing.

STEP 2: Percentage %W/V of a Given Product (25 minutes )

|Activity: Brainstorming (5 minutes) |

| |

|Ask students to brainstorm on the following question: |

| |

|What is percentage weight in volume? |

| |

|ALLOW few students to respond |

| |

|WRITE their responses on the flip chart/ board |

| |

|CLARIFY and SUMMARISE by using the content below |

• Percentage weight-in-volume indicates the number of parts by weight (gm)

of active ingredient contained in the total volume of the solution or

mixture considered as 100 parts by volume

• Weight of active ingredient in a specific volume of a solution, given its

weight-in-volume percentage strength.

o i.e. volume (mL)(represent gram)×%(expressed as a decimal)= gm of

active ingredient

• Example: 5 %( w/v) dextrose solution

o This means that 5 gm of active ingredient (dextrose powder) in every

100 mL of the
dextrose solution (i.e. 5 gm dextrose powder are in 100 mL of dextrose

solution or 5

gm of dextrose powder plus enough water to make 100 mL solution)

STEP 3: The Amount of a Product/Active Ingredient From a Given Percentage

%W/V (60 minutes)

|Activity: Small Group Discussion ( 20 minutes) |

| |

|DIVIDE students into small manageable groups |

| |

|ASK students to discuss on the following question |

|What is the percentage strength (w/v) of a solution of urea, if 80 mL |

|contains 12 gm? |

|How many gram of dextrose will be needed to prepare 200 mL of 5%w/v |

|dextrose solution? |

| |

|ALLOW students to discuss for 15 minutes |

| |

|ALLOW few groups to present and the rest to add points not mentioned |

| |

|CLARIFY and SUMMARIZE by using the contents below |

• The following are the answers of the above exercise:
80 mL of water weigh 80 gm
80 gm/ 12 gm= 100%/X%
X = (12 × 100) / 80
= 15%, answer

Weight of dextrose will be calculated as;

100%/5% = 200 mL/X mL
X= (200 × 5) / 100
= 10 gm, answer

STEP 4: Key Points (15 minutes)

• Percentage weight in volume represents the number in grams of active
ingredient/substance in 100 mL of the drug product

STEP 5: Evaluation (15 minutes)

• What is the meaning of percentage weight-in-volume?
• What do you understand by the term sodium chloride 0.9%w/v (normal

saline)?

References

Ansel, H. C & Stocklosa, M. J. (2001). Pharmaceutical Calculations (11th

ed.). Philadelphia, United States: LIPPINCOTT WILLIAMS & WILKINS

Ansel, H. C (2010) Pharmaceutical Calculations (13rd ed.). Philadelphia,

United States: LIPPINCOTT WILLIAMS & WILKINS

Senya, S. S, Mwasha, C.Y, Muyinga, A. M, Amiri,R. I. and Mauga E.A.S.K.

(2011) Tanzania Pharmaceutical Handbook (2nd ed.). Dar eS Salaam,

Tanzania: School of Pharmaceutical Sciences.

Zatz, J.L and Teixeira, M.G. (2005). Pharmaceutical Calculation (4th ed.).

New Jersey: John Wiley & Sons, Inc

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