Systems of Measurement MAT 119 Chapter 3 Objectives

Systems of Measurement MAT 119 Chapter 3

Objectives �Interpret and properly express metric and household notation. �Recall metric and household equivalents. �Explain the use of milliequivalent (m. Eq), international unit, and unit, in dosage calculation 2

Systems �There are two systems used by health professionals: metric and household. �It is important to understand each system and how to convert from one system to another. �All prescriptions should be written with the metric system. 3

Systems continued �Three essential components of measurement associated with the prescription and administration within each system: ◦ Weight ◦ Volume ◦ Length NOTE: you can move from small to large & large to small in each system, but not between differing systems. 4

The Metric System �A decimal system, which means it is based on powers of 10. �The base units of the metric system: ◦ Gram – weight ◦ Liter – volume ◦ Meter – length 5

Comparing Common Metric Units Prefix Kilo Weight kilogram Hecto Dec a BASE Deci Centi Milli Gram Milli-gram Volume Liter Milli-liter Length Meter Value To Base 1, 000 King 100 10 1 0. 1 Centimeter Milli-meter 0. 01 0. 001 Decimilli Centimilli Micro microgra m 0. 0001 ∆ Henry Died From drinking chocolate milk 0. 0000 1 X X 0. 000001 X = mcg 6

Metric System Weight Volume Length Unit Abbreviation Equivalents Gram g 1 g = 1000 mg = 1, 000 mcg Milligram mg 0. 001 g = 1 mg = 1000 mcg Microgram mcg 0. 000001 g = 0. 001 mg = 1 mcg Kilogram kg 1 kg = 1000 g Liter L 1 L = 1000 m. L Milliliter m. L 0. 001 L = 1 m. L Meter m 1 m = 100 cm = 1000 mm Centimeter cm 0. 01 m = 1 cm = 10 mm Millimeter mm 0. 001 m = 0. 1 cm = 1 mm 7

The Apothecary System �While the Joint Commission recommends the metric system be used exclusively, rarely there are some apothecary notations still in use. �Notations are unusual and can cause confusion and ultimately a medication error. 8

Household System of Measurement �Some units used in household systems ◦ ounce, pint, and quart �The unit of measure follows the amount 2 oz 25 t 375 T 5 c 9

Household System of Measurement Unit Abbreviation Equivalents drop gtt none teaspoon t (or tsp) 3 t=1 T tablespoon T (or tbs) 1 T=3 t ounce (fluid) ounce (weight) fl oz oz 2 T = 1 fl oz 1 lb = 16 oz cup (may see c) 1 cup = 8 fl oz pint pt 1 pt = 2 cups = 16 fl oz quart qt 1 qt = 2 pt = 4 cups = 32 fl oz pound lb 1 lb = 16 oz 10

Other common drug measurements �Four (4) other measurements may be used to indicate quantity of medication prescribed: ◦ International unit – unit of potency for vitamins and chemicals ◦ Unit – standardized amount needed to produce a desired effect; penicillin, heparin, insulin ◦ Milliunit – one thousandth of a unit; oxytocin ◦ Milliequivalent (m. Eq) – unit used when referring to the concentration of serum electrolytes: calcium, magnesium, potassium, and sodium 11

Units 12

Milliequivalents (m. Eq) 13