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Questions and Answers
What does % w/v indicate in pharmaceutical terms?
What does % w/v indicate in pharmaceutical terms?
How is the concentration of a powdered substance dissolved in a liquid generally calculated?
How is the concentration of a powdered substance dissolved in a liquid generally calculated?
When both drug and vehicle are liquids, how is concentration expressed?
When both drug and vehicle are liquids, how is concentration expressed?
What might affect the calculation basis in a pharmaceutical preparation?
What might affect the calculation basis in a pharmaceutical preparation?
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Which statement correctly describes the conversion of % w/w to ratio strength?
Which statement correctly describes the conversion of % w/w to ratio strength?
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Which of the following is true regarding % w/w calculations?
Which of the following is true regarding % w/w calculations?
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What is the purpose of converting weight to liquid measurements in pharmaceutical formulations?
What is the purpose of converting weight to liquid measurements in pharmaceutical formulations?
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What does the term 'weight-in-volume' (w/v) represent?
What does the term 'weight-in-volume' (w/v) represent?
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What does ratio strength indicate?
What does ratio strength indicate?
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Which formula would be used to calculate grams of drug needed for a 5% (w/w) solution?
Which formula would be used to calculate grams of drug needed for a 5% (w/w) solution?
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What is the ratio strength equivalent of a 0.02% solution?
What is the ratio strength equivalent of a 0.02% solution?
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How would you calculate the percentage (v/v) for a solution with 4 mL of phenol in 250 mL of lotion?
How would you calculate the percentage (v/v) for a solution with 4 mL of phenol in 250 mL of lotion?
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If you have 1500 g of a solution containing 75 g of a drug substance, what is the percentage strength (w/w) of the solution?
If you have 1500 g of a solution containing 75 g of a drug substance, what is the percentage strength (w/w) of the solution?
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When converting ratio strength 1:4000 to percentage strength, what does it equal?
When converting ratio strength 1:4000 to percentage strength, what does it equal?
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How many grams of a drug are needed to prepare 120 mL of a 20% (w/w) solution if the specific gravity is 1.15?
How many grams of a drug are needed to prepare 120 mL of a 20% (w/w) solution if the specific gravity is 1.15?
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To find the percentage strength (w/v) of a 800 g liquid with a specific gravity of 0.8 in 4000 mL of water, what is the formula used?
To find the percentage strength (w/v) of a 800 g liquid with a specific gravity of 0.8 in 4000 mL of water, what is the formula used?
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Study Notes
Concentration Expressions
- Concentration describes the ratio of the amount of an ingredient to the amount of the product. It can be measured in various ways.
Objectives
- Define percent weight-in-volume, percent volume-in-volume, and percent weight-in-weight.
- Define the term "ratio strength."
- Convert percent strength to ratio strength and vice versa.
- Calculate percent strength and ratio strength of a pharmaceutical preparation.
- Apply percent and ratio strength to calculate the quantity of an ingredient in a pharmaceutical preparation.
- Apply percent and ratio strength for calculating ingredient quantities in compounding.
Concentration Calculation Methods
- Solid in Liquid (w/v): Weight of solid per volume of liquid.
- Liquid in Solid (v/w): Volume of liquid per weight of solid.
- Liquid in Liquid (v/v): Volume of liquid per volume of liquid.
- Solid in Solid (w/w): Weight of solid per weight of solid.
Percentage
- Percentage relates parts of active drug to 100 parts of total.
- Incomplete notation: Must specify if it's w/w (weight-in-weight), w/v (weight-in-volume), or v/v (volume-in-volume).
- Examples provided for each type of percentage.
Special Considerations in Percentage Calculations
- The nature of ingredients dictates the calculation basis.
- Powders in liquids (weight-in-volume).
- Powders in solids/semisolids (weight-in-weight).
- Liquids in liquids (volume-in-volume).
- Converting between units (weight to liquid volume, or vice versa) may be needed.
Ratio Strength
- Ratio strength expresses concentration as parts of active drug relative to any number of parts of the whole.
- Expresses the ratio of active drug to the total amount of the product.
- 1:1000 is different than 1%.
- Examples provided for converting between ratio strength and percentage strength.
Percent Weight-in-Volume (w/v)
- Volume x percent (as a decimal) = grams of solute or constituent.
- Examples provided demonstrating the calculations.
Percent Weight-in-Weight (w/w)
- Weight of solution x percent (as a decimal) = grams of solute.
- Examples provided demonstrating the calculations.
Percent Volume-in-Volume (v/v)
- Volume x percent (as a decimal) = milliliters of active ingredient.
- Examples provided demonstrating the calculations.
Milligram per Milliliter (mg/mL), Parts Per Million (ppm)
- Other concentration expressions; examples of converting percentages to these units included.
- Parts per million (ppm) expresses the ratio of parts of a substance to one million parts of the whole.
Examples:
- Calculations demonstrating the application of the above concepts are provided throughout the notes. Specific examples involving various drugs and solution preparations (e.g., potassium permanganate, dextrose) are featured.
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Description
This quiz covers various concentration expressions used in pharmaceutical preparations. You will learn to define and convert between percent strength and ratio strength. Additionally, the quiz offers practical applications for calculating ingredient quantities in compounding based on differing concentration methods.
