D( desired ) Q( quantity) X ( amount ) H( have)

Transcription

1 Name: 3 (Pickar) Drug Dosage Calculations Chapter 10: Oral Dosage of Drugs Example 1 The physician orders Lasix 40 mg p.o. daily. You have Lasix in 20 mg, 40 mg, and 80 mg tablets. If you use the 20 mg tablets, then two tablets must be given. If you use the 80 mg tablets, then you have to cut one in half. The 40 mg tablet should be used so one whole tablet is given for the dose. It is safest and most accurate to give the fewest number of whole, undivided tablets possible. Three-Step Approach to Dosage Calculations Step 1 Convert Step 2 Think Step 3 Calculate Apply the formula : D( desired ) Q( quantity) X ( amount ) H( have) Example 2 Order: Tegretol 200 mg p.o. b.i.d. How much do you give for one dose? 1

2 Example 3 The physician orders amoxicillin 250 mg p.o. b.i.d. You have amoxicillin 250 mg per 5 ml. Example 4 The physician orders amoxicillin 250 mg p.o. b.i.d. You have amoxicillin 125 mg per 5 ml Example 5 Order: fluconazole 90 mg p.o. now Supply: fluconazole 40 mg per ml How much do you give for one dose? 2

3 Example 6 Order: Phenergan with Dextromethorphan 10 mg p.o. q.i.d. Supply: Phenergan with Dextromethorphan 25 mg per 5 ml How much do you prepare for one dose? Example 7 You need to prepare 0.3 mg of this medication. How many tablets do you need? Example 8 Order: Flagyl 2 g p.o. now Supply: Flagyl 500 mg tablets How much do you prepare? 3

4 Chapter 11: Parenteral Dosage of Drugs The term parenteral refers to any route of medication administration other than gastrointestinal. Subcutaneous (subcut), intramuscular (IM), and intravenous (IV) injections are the most common parenteral routes. Route Definition Additional Information subcutaneous intramuscular intravenous injection given into the subcutaneous tissue injection given into a muscle injection given directly into a vein The maximum dosage volume to be administered per injection site is 1 ml. The maximum dosage volume to be administered per injection site: average adult is 3 ml, children age 6 to 12 is 2 ml, and children birth to 5 years is 1 ml. Includes administration by direct injection (IV push) or diluted in a larger volume of intravenous fluid and administered as part of an intravenous infusion. The same three-step approach is used to solve parenteral dosage problems. Step 1 Convert All units of measurement to the same system, and all units to the same size. Step 2 Think Estimate the logical amount. Step 3 Calculate D( desired ) Q( quantity) X ( amount ) H( have) After determining how much medication to give for an injection, it is important to select the correct size syringe to accurately administer the dose. The syringe is chosen based upon the volume of medication you need to give, and to what place the dosage has been calculated (i.e., to the tenths or the hundredths). As you calculate parenteral dosages: 1. Round the amount to be administered (X) to tenths if the amount is greater than 1 ml, and measure it in a 3 ml syringe. 2. Round amounts of less than 1 ml to hundredths, and measure all amounts less than 0.5 ml in a 1 ml syringe. 3. Amounts of 0.5 to 1 ml, calculated in tenths, can be accurately measured in either a 1 ml or 3 ml syringe. 4

5 Example 9 Order: dilantin 100 mg IV now Available: dilantin 250 mg per 5 ml Example 10 Order: Robinul 300 mcg IV stat Supply: Robinul 0.4 mg per 2 ml How much do you prepare? Example 11 Order: ketorolac 20 mg IM q.6h p.r.n., pain Supply: ketorolac 30 mg per ml Give: ml Select syringe 5

6 Example 12 Order: Lanoxin 0.7 mg IV now Supply: Lanoxin 500 mcg per 2 ml Give: ml Select syringe Example 13 Order: Give 75 mg Dilantin IV push q.8h Supply: Dilantin 250 mg in 5 ml Calculate the amount for one dose. Draw an arrow on the syringe indicating the calibration line that corresponds to the dose to be administered. 6

7 Example 14 Order: Give Atropine 0.6 mg IM stat Supply: 20 ml vial of Atropine (0.4 mg per ml) Calculate the amount for one dose. Draw an arrow on the syringe indicating the calibration line that corresponds to the dose to be administered. Example 15 The order is heparin 7,000 units subcut q.12h. How much do you prepare for one dose? 7

8 Example 16 Order: heparin 5,000 units subcut b.i.d. Available: heparin sodium injection 10,000 units per 1 ml Insulin is a commonly prescribed medication taken by patients who have diabetes. It is critical that insulin is prepared and administered accurately because any dosage errors can be life threatening. Insulin is measured in units. The dosage strength is usually 100 units per ml, which is abbreviated on the label as U-100. Insulin has different action times, and is made from different sources. Remember to carefully read the label and compare it to the drug order to make sure that you select the correct type of insulin. Insulin orders should specify exactly which insulin is ordered, the dose, the route of administration, and the time. Sometimes a special insulin order known as a sliding scale is needed to manage a patient s blood sugar that is not yet regulated. Only regular insulin is used for sliding scale orders. The physician specifies how much insulin to give based upon the patient s blood glucose level. So the amount of insulin ordered changes, or slides up or down a specific range depending on what the blood glucose level is at the time it is given. Example 17 Order: 16 units of Novolin N NPH insulin subcut q.a.m. Supply: 10 ml vial of Novolin N NPH insulin (100 units per ml) Calculate the amount for one dose. Draw an arrow on the syringe indicating the calibration line that corresponds to the dose to be administered. 8

9 Example 18 Calculate 1 dose of each of the drug orders. The labels provided below are the medications you have available. a. Humulin R Regular U-100 insulin 22 units subcut stat Give: units b. promethazine 15 mg IM q.4h p.r.n., nausea and vomiting Give: ml 9

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11 Example 19 The patient has an order for regular insulin to be administered on a sliding scale. At 1200 the patient s glucose is 340. How much insulin would you give? Insulin Dose Glucose Reading No Coverage Glucose less than units units units units Hold insulin; call MD stat