Calculate with Confidence5th edition

Gray Morris

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Apothecary and Household Systems

Unit Two: Chapter 7

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Apothecary & Household: ObjectivesAfter reviewing this chapter, you should be able to:

1. State common apothecary equivalents2. State common household equivalents3. State specific apothecary system rules4. State specific household system rules5. Identify apothecary symbols &

measures6. Identify household symbols & measures

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Apothecary: BackgroundEnglish origin—considered to be oldestAlso called “Fraction System”Notations and Roman numerals are potentially

confusingNotations included in TJC “Do Not Use” list

TJC recommends they NOT be used in medication administration. Discouraged by ISMP.

Found on labels of older medicationsAlways convert to metric

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Apothecary: Particulars1. Abbreviation is written before unit of

measure (six grains = gr vi or gr 6)2. Roman and/or Arabic numbers are used3. Fractions indicate quantities less than 1

gr ¾

4. Fraction ½ is indicated as ss or ss—do not use

5. Can combine whole and fraction (gr 7½)

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Apothecary: Units of MeasureMinims and drams (Ʒ) no longer used – some

syringes or cups may still have markingsNurse needs to know

1 pint = 16 fluid ounces 1 quart = 32 fluid ounces = 2 pints

Weight Grain = gr Be careful not to confuse gr with g for gram Metric equivalents: gr 15 = 1 g and gr 1 = 60-65 mg

Most meds are based on the equivalent gr 1 = 60 mg

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Apothecary: Units of Measure

(cont’d)Volume

Ounce = oz Metric equivalent: 1 oz = 30 mLMedicine cups are 1 oz capacity

Although apothecary measures may still be on syringes and containers, they should always be converted to metric

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Household: BackgroundOld system and least accurateCapacities of glasses and utensils vary by

brand unless CALIBRATEDAdvise use of droppers and devices

provided with medications for accurate dosing

Memorize:1 teaspoon (t, tsp) = 5 mL1 tablespoon (T, tbs) = 15 mL1 measuring cup = 8 oz

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Households: Particulars1. Some are same as apothecary measures

Pints and quarts

2. No standard rules for expressing measures

3. Cookbook abbreviations commonly used4. Arabic numerals and fractions are used5. Smallest unit of measure is drop (gtt)

Never use as unit of measure unless delivery device is calibrated (e.g., medicine dropper or IV tubing)

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Household: SolutionsUse calibrated spoons and measuring cups!

Normal Saline (0.9%)2 teaspoons salt in 4 cups of water

Acetic Acid (0.25%)3 tablespoons of white vinegar in 4 cups of

waterUsed for some wound/dressing care and for

cleaning equipment