1. Chapter 10
Objectives
Convert among apothecary, household, and metric measurement systems
Use the correct number formats for the measurement systems
Properly format the answers

2. Apothecary Measurement and Conversion
This unit brings together the fundamental skills of the previous chapters & applies these basics to health care applications. Although new information is taught, the processes for arriving at the correct answers depend on your ability to compute using fractions, decimals, ratio, & proportion &, to a lesser degree, percents.
This unit will cover the apothecary measurements & two methods of performing apothecary. These fundamentals will help prepare you for math applications in the health care professions.
Unit 10

3. Page 218
Overview
This unit brings together the fundamental skill of the previous units and applies these basics to health care situations.
Although you will learn new information in this unit, processes for arriving at the correct answers depend on your ability to compute using fraction, decimals, ratios, proportions, and, to a lesser degree, percents.
This unit will cover apothecary measurements and two methods of converting among measurement systems.
These fundamentals will help prepare you for math applications in the health care profession.

4. Apothecary Measurement and Conversion
Page 219
Apothecary Measurement and Conversion
The apothecary system is an old measurement system that originated in England. It relies on several number systems to denote measurements: lower case Roman numerals, Arabic numerals, and fractions.
This system is being replaced by metric units to make the measuring system more uniform and avoid medication errors
Some physicians still use this system as a matter of habit so you may see labels, prescriptions, and doctors’ orders using some of these units.
This system, which uses grains fro weight and minims for volume, is used by physicians and pharmacists to calculate drug amounts.

5. Apothecary Measurement and Conversion (Cont’d)
Page 220
Apothecary Measurement and Conversion (Cont’d)
The apothecary system uses some basic rules that do not exist in other measurement systems. These rules include:
Fractions of ½ may be written as ss.
Lower case Roman numerals are used for apothecary amounts of ten or less and for the numbers 20 and 30.
The symbol is placed before the quantity: Thus, grains 7 ½ is written as grains viiss or gr. viiss
Apothecary system works with approximate equivalents!

6. Apothecary Measurement and Conversion (Cont’d)
Page 220
Apothecary Measurement and Conversion (Cont’d)
Approximate Equivalents
1 teaspoon = 5 milliliters
grain i = 65 milligrams
grain i = 1 drop
Fluid ounce 1 = 8 teaspoons
Fluid ounce 1 = 2 tablespoons
Fluid ounce 1 = 30 milliliters
1 inch = 2.54 centimeters
1 kilogram = 2.2 pounds
1 teaspoon = 60 drops
1 pint = 2 cups
1 quart = fluid ounces 32
1quart = 1 liter
1 cup = 240 milliliters
Example – page 223 – practice 1: even
Group Work – page 223 – practice 1: odd

7. Multiple Conversions Page 223
When completing multiple conversions, it is best to work within the same unit of measure before changing to another unit of measure.
For example, do all of the metric conversions, and then move to the grain conversions; or make the grain-to-metric conversion into milligrams, and then convert from milligrams to grams or micrograms.
Example – page – practice 2-3: even
Group Work – page – practice 2-3: odd

8. Converting Liquid Equivalents
Page 225
Converting Liquid Equivalents
You will convert liquid equivalents in the same manner, using ratio and proportion or dimensional analysis.
You will need a wider range of conversions to convert liquid equivalents.
Rely on the conversion charts, but work toward memorizing these equivalents so that you cane efficiently apply them.
Example – page – practice 4-6: even
Group Work – page – practice 4-6: odd

9. Rounding in Dosage Calculations
Page 229
Rounding in Dosage Calculations
The metric system is used to measure liquids, weights, and medicine. Rounding will make dealing with the applications more practical. To assist in this process, follow these five guidelines:
Any decimal number that stands along without a whole number must have a 0 placed in the whole number place.
Round decimals to the correct place value. This is somewhat dependent on your profession (for our class two decimal places).

10. Rounding in Dosage Calculations (Cont’d)
Page 229
Rounding in Dosage Calculations (Cont’d)
If the drug measurement is in metrics, the solution to the problem must be in decimals (apothecary must be in fractions).
Round only when you reach your final answer. Of note are pediatric doses, which are rounded down, not up, to avoid overdosing. The same principle is used with adults for high-alert drugs.
In some cases, it is important to place as zero at the end of the number. The trailing zero is used to show the exact level of a value such as a label result, the size of a lesion, or a catheter size.
4. Do not over-round. In medications, a small amount of medication can be critical in dosing. If you begin to round as you set up the problem, you may round again when you finalize the problem, and this can skew the dosage amount.
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Example – page 230 – practice 7-8: even
Group Work – page 230 – practice 7-8: odd