Dosage Calculation Notes PDF

Lesson 4 Dosage Calculatio ns MONECELLE JOY D. PESINABLE Instructor Apothecary Measurements* Dry Weight Fluid Volume Larger Units Smaller Units Larger Units Smaller Units 1 ounce (oz) 480 grains (gr) 1 quart (qt) 2 p...

Lesson 4 Dosage Calculatio ns MONECELLE JOY D. PESINABLE Instructor Apothecary Measurements* Dry Weight Fluid Volume Larger Units Smaller Units Larger Units Smaller Units 1 ounce (oz) 480 grains (gr) 1 quart (qt) 2 pints (pt) 1 ounce (oz) 8 drams 1 pint 16 fluid ounces (fl oz) 1 dram 60 grains (gr) 1 fluid ounce 8 fluid dram (fl dr) 1 scruple 20 grains 1 fluid dram 60 minims (min, m) 1 minim 1 drop (gtt) Metric System* Unit Names and Abbreviations Measurements 1,000 gram (g, gm, 1 kilogram (kg, Kg) G, Gm) Gram 1,000 milligram (mg) 1g (Weigh t) 1,000,000 microgram (mcg) 1 g 1,000,000,000 nanogram 1g (ng) Liter 1 kiloliter 1,000 L (l) (Volume) 1 liter (L, l) 1,000 milliliter (ml, mL) Household Equivalents* 1 measuring cup 8 ounces (oz) 1 medium-sized glass (tumbler 8 ounces (oz) size) I coffee cup (c) 6 ounces (oz); varies with size 2 tablespoons (T) 1 ounce (oz) 30 cc (ml) 3 teaspoons (t) 1 tablespoon (T) 15 cc (ml) 60 drops (gtts) 1 teaspoon (t) 5 cc (ml) 1 drop (gtt) 1 minim (min, m) Activity: Convert the following 1. 2 g to mg 2. 0.5 g to mg 3. 2.5 L to ml 4. 1,500 mg to g 5. 3 g to kg 6. 500 ml to L Body Surface Area most accurate way to calculate the drug dose for infants, children, older adults and clients who are on antineoplastic agents or whose body weight is low Nomogram: find patient’s weight in the right column and the height in the left column; place a straightedge on the nomogram so the weight and height are connected; the point where the straightedge crosses the center column denotes the patient’s body surface area in square Nomogra m Sample Question Order: methotrexate (Mexate) 50 mg weekly. Child’s height is 54 inches and weighs 90 lbs (41kg) Child’s drug dosage: 25-75 mg/m2/week Child’s height and weight intersect at 1.3 m2 (BSA) Is the prescribed dose safe? Pediatric Dosages CLARK’S RULE - weight of the child weight in lbs X AD 150 Ex. The child is weighing 50 lbs and adult dose of the drug is 30 drops, 3X a day 50 lbs X 30 drops 150 1500/150 10 drops, 3X a Pediatric Dosages FRIED’S RULE - infants (up to 1 year) age in mos. X AD 150 YOUNG’S RULE - above 1 year age in years. X AD age in years + 12 Pediatric Dosages Ex. Adult dose is 150 mg. Give mg to a 6 year- old child. Solution: Young’s age in years X Rule AD age in years + 12 6 years X 150 mg 6 years + 12 50 mg PRACTICE PROBLEM THE AVERAGE ADULT DOSE OF AMOXICILLIN IS 500MG Q8H THE CHILD WEIGHS 26LBS. HOW MANY MG PER DOSE IS NEEDED Calculating Administration Rates 2 components to remember before using the formulas drop factor of the IV administration rate amount of solution to be infused over one hour Macrodrip Set 10 drops = 1 ml 15 drops = 1 ml 20 drops = 1 ml Microdrip Set 60 microdrops = 1 ml Blood Set 10 drops = 1 ml IV Fluid Flow Rate gtts/min volume in cc X gtt factor no. of hours X 60 min/hr cc/hr volume in cc no. of hours no. of hours volume in cc cc/hr General Formula for Drug Calculation A= desired strength X stock volume stock on hand Ex. You are required to give morphine 6 mg. In your stock ampule, there is 15 mg per 1 ml. Hoy many cc will you give? 6 mg X 1 ml 15 mg = 0.4 ml Let’s Compute! 1.The physician ordered D5LR 1 L to run for 8 hours using a macroseta IV tubing with a drop factor of 15 gtts/ml. Solve for the following: a. cc/hr b. gtts/min 2.The physician ordered D5NM 1 pt to run for 10 hours, using a microset IV tubing. Solve for a. cc/hr b. mcgtts/min Let’s Compute! 3.The physician ordered D5LR 1 L to run for 25 gtts/min using a macroset with a drop factor of 15 gtts/ml. Solve for a. no. of hours b. cc/hr 4.The physician’s order read, “administer 0.02 g of furosemide (Lasix) IVTT”. Stock is 20 mg/2 ml ampule. How many cc will you prepare? Let’s Compute! 5. If Mrs. Jones weighs 65 kilograms (kg), how much does she weigh in pounds (lbs)? 6. How many ml are there in 1.2L? 7. You are assigned to administer 1 mg of morphine sulfate. On hand is 1mL vial which contains 2mg of morphine sulfate. How many mL are you going to give? Let’s Compute! 8. The order is to give 25mg of a medication. If on hand is 25,000 mcg of the same medication per tablet, how many tablets are you going to give? 9. The nurse is to infuse 1000mL of IV fluids at 125mL/hr. How many hours will it take for the nurse to change the IV bag? 10. You are to give an insulin drip IV at 20 units/hr. On hand is 250mL NS with 100units of insulin. What rate will your IV pump be in mL/hr? ? Let’s Compute! A client suffering from chest discomfort and shortness of breath is brought to the emergency department due to acute angina pectoris. The healthcare provider orders IV nitroglycerin (Nitroglycerin) 75 mg in 500 mL of 5% Dextrose Water at 100 mcg/min. The nurse will set the pump at which rate (mL/hr)?  A health care provider orders Heparin 7,855 units subq bid; Available: Heparin 10,000 units per ml. How many mL will you administer? Fill in the blanks. Record your answer using two decimal places.  A patient is receiving 160 mg of methylprednisolone (Medrol) IM every 12 hours. You have on hand two vials that each contains 125 mg/2 mL. How much will you draw into a syringe? Fill in the blanks  A health care provider prescribes phenytoin (Dilantin) 0.75 g PO stat; Available: Dilantin 250 mg cap. How many cap(s) will you administer? Fill in the blanks.  Diltiazem (Cardizem) 90 mg PO tid is ordered for a patient with hypertension. It is supplied in 60 mg scored tablets. How many tablet (s) should you administer? Fill in the blanks. Record your answer using one decimal place.