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Systems of Measurement Metric / Apothecary / Household

Systems of Measurement Metric / Apothecary / Household. Textbook Assignment: Pickar, G. (2007). Dosage calculations: A ratio-proportion approach. (2 nd ed.) Chapter 3. Revised KBurger0808. The Metric System.

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Systems of Measurement Metric / Apothecary / Household

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  1. Systems of MeasurementMetric / Apothecary / Household Textbook Assignment: Pickar, G. (2007). Dosage calculations: A ratio-proportion approach. (2nd ed.) Chapter 3 Revised KBurger0808

  2. The Metric System • The metric system is known for its simplicity. All units of measurement in the metric system are based on decimals—that is, units that increase or decrease by multiples of ten. • JCAHO recommends that the metric system by used exclusively for ordering, measuring, and reporting medications

  3. Metrication of the World The only countries not using SI Metric System are USA, Liberia and Myanmar

  4. Metric Prefixes

  5. International System (SI) of Metric Units and Abbreviations • Weight Gram (base unit)-g Milligram-mg Microgram-mcg Kilogram-kg

  6. International System (SI) of Metric Units and Abbreviations • Volume Liter (base unit)-L Milliliter-mL Cubic centimeter- cc * * the cc abbreviation should not be used as it can be mis-interpreted for zeroes if poorly written

  7. International System (SI) of Metric Units and Abbreviations • Length Meter (base unit)-m Centimeter-cm Millimeter-mm

  8. Comparing Common Metric Units

  9. Rules of Metric Notation • Unit or abbreviation always follows amount • 5 g NOT g 5 • Decimals are used to designate fractional metric units • 1.5 mL, NOT 1 mL

  10. Rules of Metric Notation • Use a zero to emphasize decimal point for fractional metric units of less than 1 • 0.5 mg, NOT .5 mg • Will prevent potential dosage error • If you misinterpreted medication order as 5 mg instead of 0.5 mg • Dosage would be 10 times too much

  11. Rules of Metric Notation • Omit unnecessary zeros • 1.5 g, NOT 1.50 g • This is a critical rule • When in doubt, double-check • Ask writer for clarification

  12. Most commonly usedMetric Measurements and Equivalents Weight

  13. Most Commonly Used Metric Measurements and Equivalents Volume

  14. The Apothecary System • Originated in Greece • First system of medication measurement • One grain = weight of a single grain of wheat [60mg] • One grain = 60 mg is the ONLY apothecary conversion you will need to memorize

  15. Apothecary System of Measurement • Currently being phased out as a system of measurement, but some units for dosage calculations that may still be seen are: • Grain (gr) • Ounce (oz) !Notice the similarity between the abbreviation for grain (gr) and gram (g). Be careful not to confuse them! • Other units in apothecary system not in use but still on some syringes and medicine cups are: minims and drams • Quantities are usually expressed in lowercase Roman numerals • Amounts greater than ten may be expressed in Arabic numbers • Except 15 (xv), 20 (xx), and 30 (xxx)

  16. Apothecary System of Measurement • Quantities of less than one are expressed as fractions, except • One-half is expressed by the symbol ss • Abbreviation or symbol is clearly written before quantity Example: gr 15 gr XV gr ½ gr ss

  17. Apothecary System of Measurement • The apothecary system is NOT recommended for use by JCAHO. • Ask the prescriber to re-write in metric or if you are unsure about the exact meaning of any medical notation • Do not guess or assume • Ask writer for clarification

  18. Household System of Measurement • Household measures are not accurate enough to be used in calculation of drug dosages. • However, when sending patients home with liquid medications, it is sometimes necessary. • Advise patients to use the measuring device provided with their prescription or an accurate measuring spoon [ not normal tableware]

  19. Units uses inHousehold Measurement • Drop (gtt) • Teaspoon (t) • Tablespoon (T) • Ounce (oz) • Cup (cup) • Pint (pt) • Quart (qt) • Pound (lb)

  20. Other Types of Drug MeasurementsUnits • Standardized amount needed to produce a desired effect • Most commonly used for medications:Insulin, Heparin, Penicillin • CANNOT be abbreviated as (U)(See JCAHO Do Not Use List) • Must be written out as the word Units

  21. Units

  22. Milliequivalents (mEq) • One thousandth of an equivalent weight of a chemical • Most commonly used when referring to concentration of electrolytes

  23. Milliequivalents (mEq)

  24. Equivalents to MEMORIZE 1 grain (gr) = 60 milligrams (mg) 1 teaspoon (t) = 5 milliliters (mL) 1 tablespoon (T) = 3 teaspoons (t) 1 ounce (oz) = 30 milliliters (mL) 1 cup = 8 ounces (oz) 1 Kilogram (Kg) = 2.2 pounds (lbs) 1 liter (L) = 1000 milliliters (mL) 1 gram (g) = 1000 milligrams (mg) 1 milligram (mg) = 1000 micrograms (mcg)

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