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Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 1 Chapter 9 Calculating Drug Dosages.

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Presentation on theme: "Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 1 Chapter 9 Calculating Drug Dosages."— Presentation transcript:

1 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 1 Chapter 9 Calculating Drug Dosages

2 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 2 Chapter 9 Lesson 9.1

3 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 3 Learning Objectives Use formulas to determine the dosages of tablets, capsules, or liquids Use formulas to determine the total number of tablets or capsules or the amount of liquid to be ordered for a specified time Use information about the apothecaries', metric, and household measurements systems to accurately calculate drug dosages

4 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 4 Learning Objectives (cont.) Calculate dosages for parenteral injections, including those for special preparations such as insulin Calculate flow rates for infusions

5 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 5 Calculating Medication Dosages Three Steps 1.Verify the drug available is the same measurement system as the drug dosage desired (convert if needed) 2. Reduce to lowest terms 3. Calculate dosage quantity to be administered

6 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 6 Drug Calculation Methods Fraction Method –600 mg = 200 mg x tablets 1 tablet Solve for x Ratios or Proportion Method –600 mg : x tablets :: 200 mg : 1 tablet –Solve for x

7 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 7 Drug Calculation Methods (cont.) Desired over Available Method Desired units (conversion factor) x Quantity of drug form = Quantity to give Quantity available (x conversion factor)

8 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 8 Forms of Oral Medications Capsules –Cannot be broken or divided –If amount to be given is more than 0.5, round to next whole number Tablets –Only divide if scored –Coated tablets are not to be broken Liquids –May be measured in a medication cup, syringe, or calibrated dropper

9 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 9 Scored and Unscored Tablets

10 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 10 Parenteral Medications Medication available in three forms: –Prefilled syringe labeled with specific dosage For example: meperidine (Demerol) 100 mg in 1 mL –Single-dose ampule or multiple-dose vial labeled with a specific dosage per volume For example: epinephrine (Adrenalin) 1:1000 in 0.1 mL –A vial with powder that requires a specific fluid be added to it to obtain a specific dosage (Reconstitution)

11 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 11 Insulin A critical medication that replaces the insulin not being produced by the patients pancreas Insulin comes in a standardized measure called a Unit Smallest amounts may be given; errors are critical

12 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 12 U-100 Vial

13 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 13 Insulin (cont.) Strengths –U-100 (100 Units of insulin per 1 mL) –U-500 (500 Units of insulin per 1 mL) Preparation 5 times stronger, rarely used Syringe Calibrated in Units also Tuberculin syringe used in emergency –Minims used; 16 minims = 1 mL

14 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 14 U-100 Syringe

15 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 15 Tuberculin Syringe

16 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 16 Intravenous Medications Medications administered into the vein –IV push –IV hanging by gravity (flow rate formula) –IV pump (mL/min or hr)

17 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 17 Flow Rate Formula Gtts/min = Volume to be administered × gtt factor Time in minutes Drop factor of tubing: Macrodrip = 10, 15, or 20 gtt/mL Microdrip = 60 gtt/mL

18 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 18 Chapter 9 Lesson 9.2

19 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 19 Learning Objectives List the rule used to calculate medication dosages for children Calculate flow rates for infusions for children

20 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 20 Clarks Rule Formula Weight of the child ________________ x Adult dose = Childs dose Weight of the adult

21 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 21 Body Surface Area Body surface area (BSA) = the total tissue area A nomogram is used to easily calculate the BSA in square meters BSA formula Surface area of the child (M 2 ) × Usual adult dose Surface area of an adult (1.73 M 2 ) = Childs dose

22 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 22 Dimensional Analysis Steps –Numbers in the dosage calculation problem are placed on a grid along with their labels –The labels are cross-canceled to assure only one label is left (one for answer) –Numbers in calculation are placed along grid next to their labels

23 Elsevier items and derived items © 2010, 2006, 2003, 2000 by Mosby, an imprint of Elsevier Inc. 23 Dimensional Analysis (cont.) –Numbers are cross-canceled –Numbers are multiplied across the top and bottom of the grid to yield a fraction –The fraction is divided, and the remaining label is applied to the answer


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