1. 1 Administering Medications to Patients Calculating medication dosages in the clinical setting Prepared for SSAC by Shari Goldberg – Colby-Sawyer College © The Washington Center for Improving the Quality of Undergraduate Education. All rights reserved. 2006 SSAC2006.WY100.SG1.1 The safe and accurate administration of medications is an essential nursing skill that takes concentration and practice. Core Quantitative Issue Ratios and Proportions Supporting Quantitative Concepts Conversions XY Scatter Plot

2. 2 Overview of Module Drug calculations are an important and valued skill for nurses. The accurate calculation of medications during administration prevents medication errors and potential harm to patients. This module is designed to take you through the process of calculating medication doses. An understanding of some basic math concepts is an important foundation when determining the amount of medication to be given to a patient. This module will give you an opportunity to practice conversions and proportions, and apply these concepts to determine accurate dosage calculations. Slide 3-4: Explanation of variables in medication administration Slide 5: Statement of a problem Slide 6-8: Review of unit conversion and decimal placement Slides 9-11: Solution of problem Slide 12-13 : end of module assignment Slides 14-16 Glossary, appendices

3. 3 Background Information: Conceptual Thinking When determining the correct amount of medication to give to a patient, there are four variables to consider: D = desired amount, or the medication order H = on hand or available medication V = the vehicle (tablet, oral suspension, injectable liquid) Order: Compazine 10 mg PO qidPO qid How many mg of Compazine are in each tablet? x = the correct medication dosage The amount of medication that you actually give to your patient How is the medication delivered?

4. 4 Background Information: Conceptual Thinking In a medication order, you will be supplied with the desired amount (D) You will be able to determine what medication is available (H). Just look at the label. The vehicle (V) is always “1” when tablets are prescribed. When injectables or oral suspensions are ordered V is the number of milliliters. The amount of medication that will be given (x), is the one unknown value that you will need to calculate. The value of x should include a number and the method of delivery such as PO or IM.POIM Order: Compazine 10 mg PO qidPO qid D = 10 mg The medication label What is the value of H? In what form will this medication be delivered? V = ? You know: how many milligrams are ordered how the medication will be delivered (tablet). So, what is the value of x? Used with permission of GlaxoSmithKline

5. 5 Problem How many milliliters of Augmentin need to be administered to Mrs. B.? How many times each day will this medication be administered? Mrs. B. is an 80-year-old woman who lives in an assisted living facility. She has been complaining of ear pain and has a history of recurring otitis media. On exam, her tympanic membrane is red and swollen. The nurse practitioner diagnoses otitis media and orders: otitis mediatympanic membrane Amoxicillin/clavulanate (Augmentin) 0.5g PO q12h.PO q12h Used with permission of GlaxoSmithKline

6. 6 Let’s review conversions within the metric system. We will create a spreadsheet to compare grams, milligrams, and kilograms. Notice on Slide 5 that the medication order is in grams and the medication label is in milligrams. You will need to convert from grams to milligrams. = cell with a number in it = cell with a formula in it Recreate the spreadsheet. Looking at the spreadsheet that you have made: What do you notice about the relationship of grams and milligrams? Grams and kilograms? If you know the value in grams, and you need to convert to milligrams, will the number in milligrams be larger or smaller? Metric Conversions, Creating a Spreadsheet The values in column B for grams will be given. Build a formula to find the values for column C (milligrams) and column D (kilograms).

7. 7 Let’s explore the information that we entered into the spreadsheet. The graph compares the number of grams with the number of milligrams. The number of grams is on the x- axis and the number of milligrams is on the y-axis. What do you notice about the graph? What happens to the number of grams when the number of milligrams increases? Why? Looking at your graph: 2.0 grams = _____ milligrams? 3500 milligrams = _____ grams? Note that metric units are used in the healthcare setting. Recreate this graph. For help click here.click here Metric Conversions, XY Scatter Plot

8. 8 Procedure: Unit conversions Use a proportion to convert the order for 0.5 g to a dosage in mg. Refer to the graph on preceding slide to check your answer. As stated in the problem on Slide 5, Mrs. B. needs 0.5 g of Augmentin. We have the medication in the medication cart, but it is in mg. You are ready to answer the question posed in Slide 5  Key To convert from the larger to the smaller unit of measure (g to mg), you want to multiply by the conversion ratio, 1000 mg per 1 g. To convert from a smaller to a larger unit (for example, g to kg), you want to divide by the conversion ratio, 1000 g per 1 kg. There are 1000 mg in 1g. Think of this as a conversion factor in the form of the ratio of the number of smaller units per one of the larger units: 1000 mg per 1 g. Also To multiply by 1000 (to convert grams to milligrams), move the decimal point three spaces to the right. To divide by 1000 (to convert grams to kilograms) move the decimal point three spaces to the left

9. 9 Solving the Problem D =500mg H=H=125mg V=V=5ml X=X=? Now that we know that we want to give Mrs. B. 500 mg of Augmentin, how many mL of the oral suspension should be administered? Return to the medication label in Slide 5. The solution is 125mg/5mL. Solving the problem calls for a proportion: How many mL of the 125mg/5mL oral suspension will deliver 500 mg of Augmentin? 2. Refer to the problem in Slide 5. Create and fill in the table below for each variable 3. Solve for X using each of the formulas below using pencil and paper : a) b) c) The answers for formulas a, b, and c are the same! Use the formula that makes the most sense to you. 1.There are a few different methods that can be used to achieve the same result when calculating medication dosages.

10. 10 Solving the Problem Recreate the spreadsheet below using the values of the variables from Slide 9, Box 2. Solve for X. Insert formula c (Slide 9, Box 3) to obtain the results for cell E3. You have identified the four variables involved in determining the correct medication dose. Use only one of the three formulas in Slide 9, Box 2 Does the value for X on your spreadsheet on this page equal the value for X that you completed on paper? = (B3/C3)*D3 So now we know the answers to questions 1&2 on Slide 5: Mrs. B. will receive 20 mL of Augmentin q 12h Mrs. B will receive Augmentin two times each day.

11. 11 Putting it all together One goal of this module is for you to understand the variables that are used to figure out the correct amount of medication to give to a patient after looking at the medication order. Let’s practice with a second example. The medication order is: Doxycycline 100 mg po bid X10d. On the medication label you note that each tablet contains 25 mg. How many tablets will you give per dose? 1.Add a new row to your spreadsheet and fill in the known variables (with the same formula that you used in Slide 10). 2. Solve for x. 3. With pencil and paper, use formula (a), (b), or (c). 4. Solve for x. Is your answer using the spreadsheet the same as the calculation you did by hand?

12. 12 Mr. P. has an order for Tagamet: 0.4g PO bid. The drugs available are:bid Bottle A Bottle B 1.What is the first thing that needs to be done? 2.What is the formula that you will use to determine the correct dosage? 3.If Bottle A is available, how will you set up the formula ? 4.How many tablets will you give Mr. P. per dose? 5. If Bottle B is available, how will you set up the formula? 6. How many tablets will you give Mr. P. per dose? End of Module Assignments 1 Used with permission of GlaxoSmithKline

13. 13 Mr. B. is one day post op, and is complaining of pain. He has an order for Demerol: 35 mg IM q4-6h as needed. The drug available is Demerol 50 mg. You are preparing to give him an injection. 7. What additional piece of information do you need? Hint: Think of the formula. 8. Calculate the amount of Demerol that you will give your patient. End of Module Assignments 2

14. 14 Important Dosage Abbreviations PO = by mouth qid = four times per day IM = intramuscular (injected into the muscle) q12h = every 12 hours bid = two times per day ReturnReturn to Slide 3 ReturnReturn to Slide 4 ReturnReturn to Slide 5 ReturnReturn to Slide 12

15. 15 Definitions Otitis media – The presence of fluid in the middle ear. Tympanic membrane – The eardrum. ReturnReturn to Slide 5

16. 16 Creating a Graph Your graph should illustrate the relationship between grams and milligrams, with grams on the x-axis and milligrams on the y-axis. You can make a graph by highlighting a range of data (here, from B2 to C21) and then clicking on the chart wizard button: Select a graph type (in this case, an X-Y scatter plot connected by a smooth line) and follow the prompts. You should enter text for your title and label each of the axes. ReturnReturn to Slide 7