Chapter 2 – Metric, Apothecary, and Household Systems of Measurement Medicine cups: marked in metric units/apothecary units/household measures Metric System Solids Kilogram kg - body weight Grams g gm - body weight (infants, premature babies) Milligram mg - pharmaceuticals Microgram mcg (μg) – pharmaceuticals (chemotherapy, hormones) 1 kg = 1000 g = 103 1 g = 1000 mg = 1, 000, 000 mcg = 106 mcg 1 mg = 1000 mcg 1 mcg = 0.001 mg = 0.000001 g Use conversion factors 10 mg x (1g ) = 0.01 g (1000mg) 2500 g x (1kg) = 2.5 kg 1000 g GRAMS TO MILLIGRAMS Decimal point is the anchor! To multiply by 1000, move the decimal point three places to the right Order: 0.25 g Supply: tablets labeled 125 mg Convert 0.25 g into mg 0.25 g x 1000mg/g = 250 mg Mg Rules 1. write the order first 2. write the equivalent measure needed 3. use an arrow to show which way decimal place should move 4. open part of the arrow always faces larger measure 5. in equivalent 1 g = 1000 mg, the gram is larger measure. (1000 mg makes up 1 g) Order: 1.5 g Supply: 500 mg Convert g to mg 1.5 g > ______ mg Note: changing an inequality into an equality 1.5 g = 1500 mg MILLIGRAMS TO GRAMS To divide by 1000, move the decimal point three places to the left Order: 15 mg Supply 0.03 g 15. mg < g 15 mg = 0.015 g Order: 500 mg Supply: 1 g 500 mg < g inequality 500. mg = 0.5 g equality Self test 2 - #9 Order: 5 mg Supply: 1 g 5 mg < g inequality 5.mg = 0.005 g equality GRAMS TO MILLIGRAMS: MOVE THREE PLACES TO RIGHT MILLIGRAMS TO GRAMS: MOVE THREE PLACES TO LEFT Changing Milligrams to Micrograms 1 mg = 1000 mcg Multiply by 1000, move decimal place 3 places to the right Example 1 Order: 0.1 mg Supply: 200 mcg 0.1 mg > ____ mcg inequality 0.1 mg = 100 mcg equality Convert 0.08 mg to mcg 0.08 mg > ____ mcg 0.080 mg = 80 mcg Changing Micrograms to Milligrams 1 mg = 1000 mcg Divide by 1000, move decimal place 3 places to the left 250 mcg = __?__ mg 250 mcg < mg 250 mcg = 0.250 mg Apothecary System Check symbols http://www.lib.umich.edu/tcp/docs/dox/medical.html http://www.mapharm.com/prescr_parts.htm Dram – liquid measure 3i = 4 mL Ounce – liquid measure gtt - liquid measure drop (guttae) m – liquid measure minim 1 dram = 4 mL 1 ounce = 32 mL 1 drop = 1 minim 1 m = 1 gtt Grain gr – solid measure แนกแนก one-half i one i แนกแนก one and a half ii iii iv 4 v vi 6 vii viii ix 9 x xi eleven xii twelve xiii thirteen xiv fourteen xv fifteen gr xv = 15 grains gr x = 0.6 g = 600 mg or 650 mg gr v = 0.3 g = 300 mg or 325 mg gr i = 0.06 g = 60 mg or 65 mg 15 grains = 1000 mg; 1 grain = 60 mg Check the manufacturer’s label Household Measures Teaspoon tsp (t) Tablespoon tbsp (T) Ounce oz (fl oz) cup c Pint pt Quart qt Pound lb Gallon gal 2 c = 1 pt 2 pt = 1 qt 4 qt = 1 gal 16 oz = 1 lb Household equivalents 1 tsp = 5 mL 3 tbsp = 15 mL 1 oz = 30 mL 1 pt = 500 mL = 0.5 L 1 qt ≈ 1 L = 1000 mL 2.2 lb = 1 kg Metric Liquid Measures Liter L Milliliter mL (ml) Cubic centimeter cc 1 mL = 1 cc 1L = 1000 mL Liquid Apothecary Measures Minim m Dram dr Ounce oz Drop gtt 1 m = 1 gtt 1 minim = 1 drop 1 dr = 4 mL 1 dram = 4 mL 8 dr = 1 oz 8 drams = 1 ounce Conversions among liquid measures 5 mL = 1 tsp 15 mL = 1 tbsp = ½ fl oz = 4 drams 30 mL = 2 tbsp = 1 fl oz = 8 drams 500 mL = 1 pt 1000 mL = 1 L = 1 qt = 2 pt 3 mL syringe Note: 1 mL = 16 minims Length Metric Meter 1m = 100 cm 1 cm = 0.01 m 1000 mm = 1 m 0.001m = 1 mm English 1 yard = 3 feet 1 foot = 12 inches 1 inch = 2.54 cm Temperature Conversion F = 9/5 C + 32 C = 5/9(F-32)