NTA Level 4 • Semester 1 • PST04105

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

Pharmaceutical Calculations • Source Session/Topic 14

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Session 14: Calculations of Percentage Strength Volume-In-Volume (%V/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 %V/V of a given product

• Calculate the amount of a product/active ingredient from a given

percentage %V/V.

Resources Needed:

• Flip charts, marker pens, and masking tape

• Black/white board and chalk/whiteboard markers

SESSION OVERVIEW

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 %V/V of a Given Product (25 minutes)

|Activity: Buzzing (10 minutes) |

| |

|ASK students to pair up and buzz on the following question for 5 |

|minutes |

| |

|What is percentage %V/V of a given product? |

| |

|ALLOW few pairs to respond and let other pairs to add on points not |

|mentioned |

| |

|WRITE their response on the flip chart/board |

| |

|CLARIFY and SUMMARIZE by using the content below |

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

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

mixture considered as 100 parts by volume

• For example: 70 %( v/v) alcohol means that 70 mL of active ingredient

(absolute alcohol) in 100 mL of the alcohol solution.

• A 0.5%v/v solution of chloroform in water contains 0.5 mL of chloroform

in 100 mL

solution (i.e. 0.5 mL chloroform plus 99.5 mL water)

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

%V/V (65 minutes)

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

volume-in-volume percentage strength.

• i.e. volume (mL) × %(expressed as a decimal)= mL of active ingredient

• This will involve the following;

Example:

• How many milliliters of liquefied phenol should be used in compounding

the following prescription?

Rx Liquefied phenol……………………2.5%

Calamine lotion………….…ad 240.0 mL

Sig. For external use

Solution:

Volume (mL) × %( expressed as a decimal) = mL of active ingredient

240 mL× 0.025 = 6 mL, answer

|Activity: Small Group Discussion ( 20 minutes) |

| |

|DIVIDE students into small manageable groups |

| |

|ASK students to discuss on the following question: |

|In preparing 250 mL of a certain solution, a pharmacist used 4 mL of |

|Liquefied phenol. What was the percentage (v/v) of Liquefied phenol in |

|the lotion? |

| |

|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 is the answer for the above exercise

%( expressed as a decimal) = mL of active ingredient/ volume (mL)

4 mL/250 mL

=0.016 × 100 mL (to get percentage)

=1.6% v/v, answer

STEP 4: Key Points (10 minutes)

• Percentage volume in volume represents the number in millilitres of

active ingredient/substance in 100 mL of the drug product

STEP 5: Evaluation (15 minutes)

• What is the meaning of percentage volume-in-volume?

• What do you understand by the term sodium chloride 0.5%v/v chloroform

solution?

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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