Pharmaceutical Measurements and Calculations 1 Presentation Topics l

Pharmaceutical Measurements and Calculations 1

Presentation Topics l l l Systems of Pharmaceutical Measurement Basic Calculations Used in Pharmacy Practice Advanced Calculations Used in Pharmacy Practice 2

Learning Objectives l Describe four systems of measurement commonly used in pharmacy and convert units from one system to another. l Explain the meanings of the prefixes most commonly used in metric measurement. 3

Learning Objectives l Convert from one metric unit to another (e. g. , grams to milligrams). l Convert Roman numerals to Arabic numerals. l Convert time to 24 hour military time. 4

Learning Objectives l Convert temperatures to and from the Fahrenheit and Celsius scales. l Round decimals up and down. 5

Learning Objectives l Perform basic operations with proportions, including identifying equivalent ratios and finding an unknown quantity in a proportion. l Convert percentages to and from fractions, ratios, and decimals. 6

Learning Objectives l Perform fundamental dosage calculations and conversions. l Solve problems involving powder solutions and dilutions. 7

Learning Objectives 1. Use the alligation method to prepare solutions. 2. Calculate the specific gravity of a liquid. 8

Systems of Pharmaceutical Measurement l l l The metric system Common measures Numeric systems Time Temperature 9

The Metric System l l Pharmacists and pharmacy techs must make precise measurements daily Most important measurements are – – Temperature Distance Volume Weight 10

Terms to Remember lmetric system –a measurement system based on subdivisions and multiples of 10; made up of three basic units: meter, gram, and liter 11

Terms to Remember l meter –the metric system’s base unit for measuring length lgram –the metric system’s base unit for measuring weight lliter –the metric system’s base unit for measuring volume . 12

The Metric System l l l Legal standard of measure for pharmaceutical measurements Developed in France in the 1700 s Has several advantages – – – Based on decimal notation Clear correlations among units of measurement Used worldwide 13

The Metric System l l Uses standardized units of Systeme International (SI) Three basic units – – – l 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 14

The Metric System An error of a single decimal place is an error of a factor of 10. . 15

The Metric System 16

The Metric System 17

Common Measures l l Common measures are approximate. Three types of common measures are used in the pharmacy: – – – l Apothecary Avoirdupois Household Common measures are often converted to metric equivalents. 18

Common Measures © Paradigm Publishing, Inc. 19

Common Measures For safety reasons, the use of the apothecary system is discouraged. Use the metric system. . 20

Common Measures . 21

Common Measures 22

Common Measures Always carefully check and double-check all calculations. 23