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Pharmaceutical Measurements and Calculations

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Presentation Topics

Systems of Pharmaceutical Measurement Basic Calculations Used in Pharmacy Practic

e Advanced Calculations Used in Pharmacy Pr

actice

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Learning Objectives

Describe four systems of measurement commonly used in pharmacy and convert units from one system to another.

Explain the meanings of the prefixes most commonly used in metric measurement.

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Learning Objectives

Convert from one metric unit to another (e.g., grams to milligrams).

Convert Roman numerals to Arabic numerals.

Convert time to 24 hour military time.

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Learning Objectives

Convert temperatures to and from the Fahrenheit and Celsius scales.

Round decimals up and down.

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Learning Objectives

Perform basic operations with proportions, including identifying equivalent ratios and finding an unknown quantity in a proportion.

Convert percentages to and from fractions, ratios, and decimals.

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Learning Objectives

Perform fundamental dosage calculations and conversions.

Solve problems involving powder solutions and dilutions.

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Learning Objectives

Use the alligation method to prepare solutions.

Calculate the specific gravity of a liquid.

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Systems of Pharmaceutical Measurement

The metric system Common measures Numeric systems Time Temperature

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The Metric System

Pharmacists and pharmacy techs must make precise measurements daily

Most important measurements are– Temperature– Distance– Volume– Weight

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Terms to Remember

metric system –a measurement system based on subdivisions and multiples of 10; made up of three basic units: meter, gram, and liter

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Terms to Remember

meter–the metric system’s base unit for measuring length

gram –the metric system’s base unit for measuring weight

liter –the metric system’s base unit for measuring volume

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The Metric System

Legal standard of measure for pharmaceutical measurements

Developed in France in the 1700s Has several advantages

– Based on decimal notation– Clear correlations among units of measurement– Used worldwide

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The Metric System

Uses standardized units of Systeme International (SI)

Three basic units– Meter (distance, little use in pharmacy)– Gram (weight, used for solid form meds)– Liter (volume, used for liquid meds)

Numbers expressed as decimals rather than fractions

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The Metric System

An error of a single decimal place is an error of a factor of 10.

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The Metric System

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The Metric System

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Common Measures

Common measures are approximate. Three types of common measures are used

in the pharmacy:– Apothecary– Avoirdupois– Household

Common measures are often converted to metric equivalents.

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Common Measures

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Common Measures

For safety reasons, the use of the apothecary system is discouraged. Use the metric system.

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Common Measures

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Common Measures

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Common Measures

Always carefully check and double-check all calculations.