Math for Pharmacology Dr J Domenech Pearsons Comprehensive

Math for Pharmacology Dr. J. Domenech Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Systems for Calculating Medication Doses • Apothecary • Metric Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Basic Units of Measure Using the Apothecary System • • • Grain Gram Dram Ounce Pound Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Fluid Measurements of the Apothecary System • • • Minims Fluid dram Fluid ounce Pint Quarter Gallon Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Accurately Writing an Apothecary Notation • Place the unit or abbreviation before the amount • Use lowercase roman numerals to express whole numbers 1 through 10, 15, 20, and 30 • Use Arabic numbers for other quantities • Use fractions to designate amounts less than w • The symbol ss is used to designated the fraction 1/2 Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

The Metric System • Most commonly used conversion system for dosage calculations • Accomplished by multiplying or dividing by 1, 000 Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Common Units of the Metric System • Liter (volume) • Gram (weight) • Meter (length) Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Factors to Consider When Calculating a Patient’s Dosage • • Age Weight Current state of health Other medications the patient is taking Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Review of Math Principles • • Fractions Ratios Percentages Decimals Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Calculation Formula • • Available strength Available amount Ordered strength Amount to give available strength available amount ----------- = ----------ordered strength amount to give Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips 500 mg 1 cc ====> ---- = ----350 mg x cc © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Guidelines for Conversion • To change grains to grams, divide by 15 • To change ounces to cubic centimeters or milliliters, multiple by 30 • To change grains to milligrams, multiply by 60 • Use only when you have less than 1 grain • To change kilograms to pounds, multiple by 2. 2 • To change cubic centimeters or milliliters to ounces, divide by 30 Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Guidelines for Conversion (cont’d) • To change drams to milliliters, multiply by 4 • To change cubic centimeters or milliliters to minims, multiply by 15 or 16 • To change minims to cubic centimeters or milliliters, divide by 15 or 16 • To convert drams to grams, multiply by 4 Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Rules for Calculating Pediatric Medications • Clark’s Rule • Fried’s Law • Young’s Law Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Methods for Calculating Pediatric Dosages • West nomogram • Body weight • Child Pediatric Dose - West Nomogram Rule Formula: Childs dose = (BSA of child / 1. 73 m 2) x Adult dose Where BSA = is Body Surface Area. Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458

Summary • • Apothecary system Metric system Math principles Calculation formula Guidelines for conversion Rules for calculating pediatric medications Methods for calculating pediatric dosages Pearson’s Comprehensive Medical Assisting Beaman / Fleming-Mc. Phillips © 2007 Pearson Education, Inc. Pearson Prentice Hall Upper Saddle River, NJ 07458