Metric Conversions, Roman Numerals, and Fractions
Introduction Pharmacy measurements come from different regions of the world The four most common types of calculation systems are: Metric system Household measurements Apothecary system Avoirdupois system The avoirdupois (AH-vair-duh-PWAH) system is actually the name of one type of weights in the English (or British Imperial) system of weights and measures.
Metric System Used throughout pharmacy because of its accuracy Metric units include: Milliliters, cubic centimeters, and liters for volume Kilograms, grams, milligrams, and micrograms for weight Millimeters and meters for distance In what fields is the metric system commonly used in the United States? The metric system is the standard for use in laboratories and in scientific publications. The formal name for the metric system is SI, which is the abbreviation for Systèm International d’Unités. Is the United States ever going to switch to SI? Federal agencies are now required to use the metric system. Private industries are now voluntarily converting (for example, nuts and bolts in automobiles) to be more competitive internationally.
Metric System (Continued) There is a 1000-unit difference between each measurement Most Common Metric Measurements kg______g________mg________mcg 1000x 1000x 1000x
Metric System (Continued) The use of millimeters is reserved for drug calculations based on body surface areas Knowing the basics for volume and weight conversions is adequate What types of drugs might require body surface calculations? Topical preparations such as creams and ointments might require an estimate of body surface area.
Writing Units Using Each System (Continued) Metric measurements cc and ml can be used interchangeably Dry weights use mcg, mg, g, and kg Liquid volumes use ml and L
Household Measurements The most common measurement system still used in the United States is the household system Measurements come in a variety of units Volume refers to liquids Weight refers to dry ingredients Length refers to distance Most common measurement is the teaspoon The U.S. Customary System is the official name for the system of household measurements. It’s also a subset of the English/Imperial system.
Common Household Measurements Household Measurements Metric (Volume) (Volume) Household 1 teaspoon 5 ml or cc* 1 teaspoon 1 tablespoon 15 ml or cc 3 teaspoons 1 cup 240 ml or cc 8 ounces 1 pint 480 ml or cc 2 cups 1 quart 960 ml or cc 4 cups 1 gallon 3840 ml or cc 16 cups or 3.84 L *Remember that 1 ml and 1 cc contain the same amount of liquid.
Oral cups show equivalent volumes between household to metric and household to apothecary.
Conversions Metric system slide When converting metric measurements from one unit to another you need to move the decimal either to the right or to the left All changes of the metric system involve either dividing or multiplying by tens Each unit is a multiple of 1000 Remember the difference between 1 kg, 1 g, 1 mg, and 1 mcg is 1000 What are the base metric units for mass, volume, and length? The base units are the words without any prefixes: grams for mass, liters for liquid, and meters for length.
Conversions (Continued) Method for determining metric conversions Left Right Largest Smallest 1________1_______1_________1 1 kg 1000 g 1,000,000 mg 1,000,000,000mcg
Conversions (Continued) Decimals are not placed at the end of a number unless there is a fraction, such as 1.1 kg Decimals and periods have been the main source of mistakes in pharmacies
Determining Weight Because all manufacturers provide proper dosing regimens based on kilograms, it is necessary to convert pounds into kilograms There are 2.2 pounds per kilogram 16 ounces = 1 lb 2.2 pounds = 1 kg To determine how many kg in 1 lb, divide To determine how many lbs in 1 kg, multiply A way to remember the pounds to kilogram conversion is that you “lose weight” when going from pounds to kilograms. For example, a 220-pound person weighs 100 kilograms.
Determining Length Metric Household/English 1 meter 39.372 in / 3.281 ft 0.914 meter 3 feet / 1 yard 0.3048 meters 12 inches / foot 2.54 cm 1 inch
Roman Numerals The number system commonly used in the United States is the Arabic system, consisting of numbers 1, 2, 3, and so forth Many physicians use Roman numerals to indicate the quantity of tablets or capsules to be filled or to order the strength of medication What is the current year in Roman numerals? 2006 = MMVI 2007 = MMVII 2008 = MMVIII
Roman Numerals (Continued) 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 However, if a smaller number is placed before a larger number, then you must subtract Remember that you can only place a letter for the next power of 10 “size down” to the left of a letter. For example, you can’t take the shortcuts IC for 99 or VC for 95 because I (1) and V (5) are more than one power of 10 smaller than C (100).
Roman Numeral Practice XIV = XC = CIV = XL = VIII = C = IV =
Military Time In hospital settings, international time, also known as military time, is used exclusively 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
Military Time (Cont’d) 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 Do not use a colon to separate hours and minutes. It might seem redundant and confusing, but a slight distinction can be made between 2400 and 0000. The end of a day is 2400, and the beginning of the next day is considered 0000.
Practice! Grab a white board and a marker!
Question #1 A mother was told to give her 3 year old a ¼ cup of water every 4 hours. In 24 hours she will give the child ___ A. 6 fluid ounces B. 8 fluid ounces C. 10 fluid ounces D. 12 fluid ounces
Answer #1 D – 12 fluid ounces 24 hours / every 4 hours = 6 doses 6 doses x ¼ c = 1 ½ cups total 1 c = 8 oz 1.5c x 8 oz = 12 fluid ounces
Question #2 You assist a patient in wrapping an ace bandage around the leg. You use 30 cm. of ace bandage. How many inches did you use? A. 12 inches B. 75 inches C. 914.4 inches D. 1000 inches
Answer #2 A = 12 inches 1 inch = 2.54 cm 30 cm / 2.54 = 11.81 inches
Question #3 How many days will an 8-ounce bottle of medication last, if an adult takes the maximum dose of 2 tsp. every 8 hours? A. 8 days B. 10 days C. 15 days D. 30 days
Answer #3 A – 8 days 1 oz = 30 ml, 5 ml = 1 tsp 8 oz x 30ml = 240 ml 240 ml / 5 ml = 48 tsp in the bottle 48 tsp in bottle / 2 tsp dose = 24 doses Dose every 8 hours / 24 hrs in a day = 3 doses per day 24 doses / 3 doses per day = 8 days
Question #4 The doctor ordered 0.25 g. of a medication for the patient. The medication comes in 125 mg per 5 cc's. You should give _____. A. 2½ cc B. 5 cc C. 7½ cc D. 10 cc
Answer #4 D = 10cc 1g = 1000mg 0.25g x 1000mg = 250mg 250mg / 125mg = 2mg 5cc’s per every 125mg 2mg x 5cc’s = 10cc
Question #5 A medical records clerk is asked to collect records regarding cancer patients. It is found that a ¼ of the records relate to breast cancer. There are a total of 20,920 records. How many are related to breast cancer? A. 83,680 B. 10,460 C. 5,230 D. 2,660
Answer #5 C = 5,230 records 20, 920 / 4 = 5,230
Question #6 Your friend is 65" tall. This is equal to A. 0.65 meters B. 1.625 meters C. 6.50 meters D. 16.25 meters
Answer #6 B = 1.625 meters 1 meter = 1000mm = 100cm 10 mm = 1cm 2.54cm = 1 inch 65 inches x 2.54cm = 165.1 cm 165.1cm / 100cm = 1.651 m
Question #7 You take a patient's temperature and find it is 102°F. You are to record the temperature as A. 24.66° C B. 34.22° C C. 38.89° C D. 70 °C
Answer #7 C = 38.89 C Formula: C = (F – 32)5 / 9 102F – 32 = 70 70 x 5 = 350 350 / 9 = 38.89C
Question #8 You are to use a needle, 3 inches long, to give an injection. How many mm. is this? A. 7.5 mm. B. 25.0 mm. C. 75.0 mm. D. 100.0 mm.
Answer #8 C = 75.0 mm 1 cm = 10 mm 3in x 2.54 cm = 7.62 cm 7.62 cm x 10mm = 76.2mm * A 75mm needle is a standard size*
Question #9 Marjorie has joined Weight Watchers. She would like to lose 12 kg in 30 days. On the average, how many pounds per day will Marjorie lose to meet her goal? A. 0.44 lbs. B. 0.88 lbs. C. 1.1 lbs. D. 2.5 lbs.
Answer #9 B = 0.88 lbs. 1kg = 2.2 lbs. 12kg x 2.2 lbs = 26.4 lbs. 26.4 lbs / 30 days = 0.88 lbs.
Question #10 You are to administer meds to a patient at 2030 military time. What time is that? A. 8:30am B. 10:30am C. 12:30pm D. 8:30pm
Answer #10 D = 8:30 pm