systems of measurement

Systems of measurement

objectives

• Apothecary system• Metric system• Abbreviations

Apothecary systems

• Apothecary system is one of the oldest systems of measurement.

• Uses fractions, as opposed to decimals.• Is less accurate than the metric system.

Terminology

• the system used by an apothecary• a system of measurement used in

pharmacy prior to the metric system

• units of measure include minims, fluidrams, scruples, grains, ounces, and pounds

apothecary system

Apothecary Volume and Weight Equivalences

Apothecary Volume and Weight Equivalences

Apothecary Volume and Weight Equivalences

apothecary pound = 12 oz

household pound = 16 oz

Conversions between the Apothecary and the Metric

Systems

• Use equivalent measures to convert between units in the apothecary system.

• As a general rule, convert all quantities to the metric system as soon as possible.

Volume Equivalents

Volume Equivalents

There are actually 3.75 mL in 1 fluidram. However, convention dictates that 1 fluidram = 1 tsp = 5 mL.

Volume Equivalents

There are actually 29.57 mL in 1 fluidounce, but 30 mL is usually used

Weight Equivalents

Weight Equivalents

Many manufacturers use 60 mg instead of 65 mg as the equivalent for 1 grain.

Terminology

the smallest unit of measure in the apothecary system

grain

Conversions between the Apothecary and the Metric

SystemsConverting Grains

• The units of grains appears on nitroglycerin, along with milligram equivalent.

• Most pharmacists use 1 gr = 65 mg, but some sources indicate 1 gr = 60 mg.

Metric system

• Kg- Kilogram• L- Liter• mcg- microgram• mEq- milliequivalant• mg- milligram• mL- milliliter• μg- microgram• μgtt- micro drop• gm-gram

Safety Note!Many manufacturers use 60 mg instead of 65 mg as the equivalent for 1 grain. Read the label to confirm the package contents.

Conversions between the Apothecary and the Metric

SystemsConverting Fluidounces

Remember

16 fl oz = 480

1 fl oz = 30 mL

Lbs. to Kg

• There are two methods that may be used to convert pounds to Kg:

• Lbs./ 2.2 = Kg• Therefore, if you need to convert Kg to Lbs:• Kg x 2.2 = Lbs.

Metric Conversions

• Kg, g, mg, mcg• Lbs. to Kg• L to mL

Kg, g, mg, mcg

• To convert if going from large value to smaller value, move the decimal point 3 places to the right for each conversion.

• If going from smaller value to larger value, move the decimal point 3 places to the left for each conversion.

• 3.0 Kg = 3000. g = 3000 g• 3.0 Kg = 3000000. = 3,000,000 mg• 3.0 Kg = 30000000 00. =• 3,000,000,000 mcg

L to mL

• 1 L = 1000. = 1,000 mL• 500 mL = 500. = .5 L

Conversions to mg

• 300 mcg = 3 mg• 6 Kg = 6,000,000 mg• 14 g = 14,000 mg• 1,000 mcg = 1 mg

Conversions to mcg

• 1 g = 1,000,000 mcg• 0. 452 mg = 452 mcg• 0.010 mg =10 mcg• 0.0006 Kg = 600,000 mcg

Conversions to g

• 0.043 Kg = 43 g• 100,000 mcg =0 .1 g• 1,000 mg = 1 g• 0.075 mg =0.000075 g• 1,500 mcg = 0 .001500 g• 1 Kg = 1,000 g

Conversions to Kg

• 1000 g = 1 Kg• 1,500 mg = 0.0015 Kg• 0.042 mg = 0.000000042 Kg• 720,000,000 mcg = 0 .72 Kg

Lbs. to Kg

• 275 Lbs. = 125 Kg• 100 Lbs. = 45 Kg

Kg to Lbs.

• 100 Kg = 220 Lbs.• 32 Kg = 70 Lbs.

L to mL

• 2 L = 2,000 mL• 0.5 L = 500 mL• 1 L = 1,000 mL• 0.250 L = 250 mL

mL to L

• 3,000 mL = 3 L• 1,500 mL = 1.5 L• 500 mL = 0.5 L

mL v. cc

• A mL and a cc have the same value.• Therefore:• 1 mL = 1 cc• 500 mL = 500 cc• 0 .5 cc = 0.5 mL

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