Pharmaceutical Calculations Intravenous Infusions Parenteral Admixtures and RateofFlow

Pharmaceutical Calculations: Intravenous Infusions, Parenteral Admixtures, and Rate-of-Flow Calculations Danielle Del. Villano, Pharm. D.

Objectives • Perform calculations for the adult and pediatric intravenous infusions • Perform calculations for intravenous additives • Perform rate-of-flow calculations for intravenous fluids

Introduction • Injections – Intravenous, intramuscular, intradermal • Parenteral administration – Anything other than enteral route • Intravenous infusions – IVPB, IV push, large volume parenteral • Administration set – Certain number of drops per m. L

Problem 1 • How many grams of dextrose and sodium chloride are used to prepare a 250 m. L bag of D 51/2 NS for intravenous infusion? 250 m. L * 0. 05 = 12. 5 g dextrose 250 m. L * 0. 0045 = 1. 125 g sodium chloride

Problem 2 • A physician orders enalaprilat (Vasotec IV) 2 mg IVP for a hypertensive patient. A pharmacist delivers several 1 m. L injections, each containing 1. 25 mg enalaprilat. How many m. L of the injection should be administered? 1. 25 mg = 2 mg 1 m. L x = 1. 6 m. L

Problem 3 • Calculate the daily infusion volume of D 10 W to be administered to a neonate weighing 3 lb 8 oz on the basis of 60 m. L/kg/day. 3 lb 8 oz --> 3. 5 lbs = 1. 6 kg 2. 2 60 m. L/kg/day* 1. 6 kg = 96 m. L/day

Problem 4 • An intravenous infusion is to contain 15 m. Eq of potassium ion and 20 m. Eq of sodium ion in 500 m. L D 5 W. Using potassium chloride containing 6 g/30 m. L and 0. 9% NS injection, how many milliliters of each should be used to supply the required ions? KCl Na. Cl 1 m. Eq = 74. 5 mg 1 m. Eq = 58. 5 mg 15 m. Eq x mg 20 m. Eq x mg x = 1118 mg x = 1170 mg 6 g = 1. 118 g 0. 9 g = 1. 17 g 30 m. L x m. L 100 m. L x = 5. 6 m. L x = 130 m. L

Rate of Flow Equations • Rate (drops/min) = Vol (m. L) * dripset (drop/m. L) Time (min) • Infusion time = Vol (m. L) Rate (m. L/min)

Problem 5 • A medication order calls for 1000 m. L of D 5 W to be administered over an 8 hour period. Using an IV administration set that delivers 10 drops/m. L, how many drops per minute should be delivered to the patient? Rate = 1000 m. L * 10 drops/m. L (8 hr * 60 min/hr) Rate = 20. 8 or 21 drops/min

Problem 6 • An intravenous infusion contains 10 m. L of a 1: 5000 solution of isoproterenol hydrochloride and 500 m. L of a 5% dextrose injection. At what flow rate should the infusion be administered to provide 5 mcg of isoproterenol hydrochloride per minute, and what time interval will be necessary for the administration of the entire infusion?

Problem 6 1 g 5000 m. L x = xg 10 m. L =. 002 g = 2 mg 2000 mcg = 5 mcg 510 m. L x = 1. 28 m. L per minute 1. 28 m. L 1 min x = 510 m. L x min = 398 minutes, or ~6. 5 hours

Questions

Reference • Ansel, H. C. (2009) Phamaceutical Calculations (13 th Ed. ). Philadelphia: Lippincott Williams & Wilkins, and Wolters Kluwer Publishers

Additional Problems

Chapter 13 Page 219 • A physician prescribes amiodarone HCl IV (Cordarone) for a patient with ventricular fibrillation. The prescribing information is – Loading infusion • Rapid infusion over first 10 min • Slow infusion over the next 6 hours 15 mg/min 1 mg/min • Slow infusion over the remaining 18 hours 0. 5 mg/min – Maintenance infusion • Amiodarone HCl IV is available in 3 m. L ampuls containing 50 mg/m. L. The pharmacist uses a 100 m. L bag of D 5 W for the rapid infusion and 250 m. L bottles of D 5 W for the slow infusion.

Chapter 13 Page 219 • How many milliliters from an amiodarone HCl IV ampul should be placed in the 100 m. L bag for the rapid infusion? • What is the drug concentration in the rapid infusion, in mg/m. L?

Chapter 13 Page 219 • If the pharmacist added the contents of 3 ampuls to each 250 m. L bottle of D 5 W needed for the slow infusions, calculate the drug concentration in mg/m. L • What rate of administration, in m. L/hr, should the pharmacist have recommended during the 6 hour infusion segment?

Chapter 13 Page 219 • Calculate the rate of administration in the last question in drops/minute with an administration set that delivers 15 drops/m. L • Calculate the milligrams of drug administered by slow infusion over the 6 hour segment

Chapter 13 Page 219 • Make the same calculation as in the last question but over the 18 hour segment

Chapter 13 Problem 3 • A patient received 250 m. L of an infusion at a rate of 40 m. L/hr. What was the total infusion time in hours and minutes?

Chapter 13 Problem 9 • An emergency syringe contains lidocaine, 1 g/5 m. L. How many milliliters should be used in preparing 250 m. L of an infusion to contain 4 mg/m. L of lidocaine in D 5 W?

Chapter 13 Problem 13 • A pharmacist receives a medication order for 300, 000 units of penicillin G potassium to be added to 500 m. L of D 5 W. The directions on the 1, 000 -unit vial state that if 1. 6 m. L of solvent are added, the solution will measure 2 m. L. How many milliliters of the solution must be withdrawn and added to the D 5 W?

Chapter 13 Problem 21 • How many milliliters of an injection containing 1 g of drug in 4 m. L should be used in filling a medication order requiring 275 mg of the drug to be added to 500 m. L of D 5 W solution? If the solution is administered at the rate of 1. 6 m. L per minute, how many milligrams of the drug will the patient receive in 1 hour?

Chapter 13 Problem 31 • If a physician orders 5 units of insulin to be added to a 1 -liter intravenous solution of D 5 W to be administered over 8 hours, (a) how many drops per minute should be administered using an IV set that delivers 15 drops/m. L, and (b) how many units of insulin would be administered in each 30 -minute period?

Chapter 13 Problem 48 • CARDENE IV (nicardipine hydrochloride) is administered in the short-term treatment of hypertension by slow intravenous infusion at a concentration of 0. 1 mg/m. L. A 10 -m. L ampule containing 25 mg of nicardipine hydrochloride should be added to what volume of D 5 W to achieve the desired concentration of infusion? – (a) 80 m. L – (b) 100 m. L – (c) 240 m. L – (d) 250 m. L