Metric Conversions Roman Numerals and Fractions 1 Introduction

Metric Conversions, Roman Numerals, and Fractions 1

Introduction l The ability to manipulate conversions is a required competency of pharmacy technicians l It is a foundation for filling orders and calculating dosages in the pharmacy l All transcribing calculations need to be checked by a pharmacist 2

Introduction (Continued) l Pharmacy measurements come from different regions of the world l The four most common types of calculation systems are: l Metric system l Household measurements l Apothecary system l Avoirdupois system 3

Introduction (Continued) l. A good way to become familiar with common pharmacy measurements is to start with what you know and then slowly build on that knowledge l The pharmacy technician must translate the doctor’s orders into lay terms l You must make the instructions easy enough for a child to understand 4

Metric System l Used throughout pharmacy because of its accuracy l Metric units include: l Milliliters, cubic centimeters, and liters for volume l Kilograms, milligrams, and micrograms for weight l Millimeters and meters for distance 5

Metric System (Continued) l There is a 1000 -unit difference between each measurement Most Common Metric Measurements kg________mg____mcg 1000 x 6

Metric System (Continued) l The use of millimeters is reserved for drug calculations based on body surface areas l Knowing the basics for volume and weight conversions is adequate 7

Writing Units Using Each System (Continued) l Metric measurements cc and ml can be used interchangeably l Dry weights use mcg, mg, g, and kg l Liquid volumes use ml and L l 8

Household Measurements The most common measurement system still used in the United States is the household system l Measurements come in a variety of units l Volume refers to liquids l Weight refers to dry ingredients l Length refers to distance l Most common measurement is the teaspoon l 9

Common Household Measurements (Volume) 1 teaspoon 1 tablespoon 1 cup 1 pint 1 quart 1 gallon Metric (Volume) 5 ml or cc* 15 ml or cc 240 ml or cc 480 ml or cc 960 ml or cc 3840 ml or cc or 3. 84 L Household 1 teaspoon 3 teaspoons 8 ounces 2 cups 4 cups 16 cups *Remember that 1 ml and 1 cc contain the same amount of liquid. 10

Apothecary System l Originated in Europe l Units used in this system are grains and scruples for dry weight l Drams and minims for liquids l More common measurements include ounces and pounds 11

Writing Units Using Each System (Continued) l Apothecary measurements Dry weights use pounds, ounces, drams, scruples, and grains l Liquid volume weights use gallons, pints, fluid ounces, fluid drams, and minims l 12

Apothecary Weights Dry Weight 1 grain 15 grains 20 grains 1 dram 1 ounce 1 pound = = = = 60 mg 1 gram Э 1 Э 3 8 or Э 24 gr 480 31. 1 grams 16 ounces 96 Э 288 gr 5760 454 grams Fluid Weight 1 dram 8 drams 3 scruples* = 60 = 480 =1 *Scruples and minims are not commonly used units 13

Important Differences Among Systems l The metric system is used for compounding drugs l There are differences among manufacturer’s products and their weights l Conversions with these variances are approximate l A pint can be 473 ml, 480 ml, or 500 ml l 1 pound = 454 g in metric, but only 373 g in the apothecary system 14

Conversion Table: Apothecary/Metric/Household Apothecary Volume Apothecary Weight Metric Volume Metric Weight Common Household 1 1 30 ml 30 g 2 tbsp 4 4 15 ml 15 g 1 tbsp 2 2 7. 5 ml 7. 5 g ½ tbsp 1 gr 60 4 ml 4 g 1 tsp 2 ml 2 g ½ tsp ½ gr 30 15

Oral cups show equivalent volumes between household to metric and household to apothecary. 16

Avoirdupois System l Originated in England l Similar to the apothecary system because it also uses grains, ounces, and pounds for weight 17

Conversions l Metric system slide l When converting metric measurements from one unit to another you need to move the decimal either to the right or to the left l All changes of the metric system involve either dividing or multiplying by tens l Each unit is a multiple of 1000 l Remember the difference between 1 kg, 1 mg, and 1 mcg is 1000 18

Conversions (Continued) l Method for determining metric conversions Left Largest Right Smallest 1____1_________1 kg 1000 g 1, 000 mg 1 1, 000, 000 mcg 19

Conversions (Continued) l Decimals are not placed at the end of a number unless there is a fraction, such as 1. 1 kg l Decimals and periods have been the main source of mistakes in pharmacies 20

Conversions (Continued) l When converting from large to small, you multiply l When converting from small to large, you divide 21

Conversions (Continued) l Fractions l Percentage is always a portion of 100 l To convert a decimal into a percentage you simply multiply by 100 22

Determining Weight l. Because all manufacturers provide proper dosing regimens based on kilograms, it is necessary to convert pounds into kilograms l. There are 2. 2 pounds per kilogram l 16 ounces = 1 lb 2. 2 pounds = 1 kg l. To determine how many kg in 1 lb, divide l. To determine how many lbs in 1 kg, multiply 23

Roman Numerals l The number system commonly used in the United States is the Arabic system, consisting of numbers 1, 2, 3, and so forth l Many physicians use Roman numerals to indicate the quantity of tablets or capsules to be filled or to order the strength of medication 24

Roman Numerals (Continued) l When working with Roman numerals, remember that if a larger number is placed in front of a smaller one, you must add both to determine the value l However, if a smaller number is placed before a larger number, then you must subtract 25

Roman Numerals (Continued) l When a numeral is repeated, its value is repeated. l A numeral may not be repeated more than 3 times. l V, L, & D are never repeated. l When a smaller numeral is placed before a larger numeral, it is subtracted from the larger numeral: Ex: XC=100 -10=90 26

Roman Numerals cont’d l When a smaller numeral is placed after a larger numeral, it is added to the larger numeral. Ex: CL=100+50=150 l V, L, & D are never subtracted. Ex: LC is incorrect. l Never subtract more than one numeral. l When subtracting, only use a numeral before the next 2 higher-value numerals. Ex: use I 27 before V & X, X before L & C

Roman Numeral Practice l XIV = l XC = l CIV = l XL = l VIII = l. C = l IV = 29

Military Time l In hospital settings, international time, also known as military time, is used exclusively l Orders are written 24 hours a day and all medical-related caretakers must understand exactly when the order was written and when the medication or treatment is to take place 30

Military Time (Cont’d) l l The system is based on 100 Starting with the first hour of the day, the clock begins at 0100 (1 AM) through 2400 or 12 midnight By using this system there is never any question as to when an order was written or which order came first Never use a colon

Your Assignments l l The room is separated in halves Students on the side of the room by the windows will create 15 practice exercises using Roman numbers (and an answer key) Students on the side of the room by the door will create 15 practice exercises converting military time to standard and standard to military (15 total exercises). When finished, work all problems on the document camera. Call on students using craft sticks or allow them to work as a team 32