ISOTONICITY TUTORIAL CALCULATING E VALUE Number of dissociated ions Dissociation factor (i) 1 1 2 1.8 3 2.6 4 3.4 5 4.2 (58.5) π E value = (ππ ππ πππ’π) (1.8) E value tells you how many grams of NaCl equivalents there are in 1 g of drug Ex: Boric acid has an E value of 0.52 This means there are 0.52 g of NaCl equivalents per 1 g of boric acid. This also means there are 0.52 mg of NaCl equivalents per 1 mg of boric acid. 0.52 π πππΆπ 1 π πππππ ππππ E value is a conversion factor used to convert g NaCl ↔ g drug β β You need an E value for every ingredient in your order that is not water or NaCl. You also need an E value if your isotonicity agent (i.e. what you are adding to make the solution isotonic) is not sodium chloride 1. Calculate the E value for ephedrine sulfate (MW = 429), which dissociates into 3 ions. (Round the ο¬nal answer to the nearest TENTH) STEPS TO COMPLETING ISOTONICITY PROBLEMS 1. Calculate the necessary E values. If you already have them, skip this step. (E) 2. Calculate the total amount of NaCl needed to make the product isotonic. (Goal: Vol, NS) a. Pretend your volume of product = volume of NS. b. How many g of NaCl are in that volume of NS? c. Find out by multiplying your desired volume by 0.9 g NaCl/100 mL. This is how many total grams of NaCl are needed to make your product isotonic. 3. Calculate the total amount of NaCl equivalent contributed by each ingredient. (Have: gdrug x E) a. Multiply the total amount of each drug/ingredient (in grams) by the E value of the drug. This is how many g NaCl are being contributed by the ingredient b. If there are multiple ingredients, repeat for each ingredient and then add up the total amount of NaCl equivalents. 4. Find the amount of NaCl that needs to be added to make the product isotonic. (g NaCl Needed = G - H) a. Subtract Goal - Have to ο¬nd how many grams of NaCl should be added to make the product isotonic. (Need = Goal - Have) 5. Any other conversions you may need to do. (Ask) a. Ex: i. If they are asking for mg of NaCl, convert g NaCl from step 4 to mg ii. If you are asked for mL of 3% NaCl, convert g NaCl from step 4 to mL 3% NaCl iii. If you are asked for g of an isotonicity agent that is NOT NaCl (common ones include boric acid and zinc chloride), use the E value of the isotonicity agent to convert g NaCl from step 4 → g of the agent (i.e. divide by the E value) For example, if you were to use zinc chloride (E value = 0.62) to adjust tonicity, you would divide by 0.62. SAMPLE PROBLEM: Part 1 A pharmacist receives the following order: Ephedrine sulfate 0.3 g Sodium chloride qs Puriο¬ed water ad 30 mL Make isotonic solution Sig. Use as directed If the E value of ephedrine sulfate is 0.2, how many milligrams of sodium chloride should be used in compounding the prescription? (Round the ο¬nal answer to the nearest WHOLE number) 1. Calculate the necessary E values (E value) 2. Calculate the total amount of NaCl needed to make the product isotonic. (Goal: Vol, NS) 3. Calculate the total amount of NaCl equivalent contributed by each ingredient. (Have: ging x E) 4. Find the amount of NaCl that needs to be added to make the product isotonic. (Need to add = Goal - Have in g NaCl) Part 2 Suppose the pharmacist will use 3% sodium chloride to adjust the tonicity in the above scenario. How many mL of 3% sodium chloride should be added to the product? (Round the ο¬nal answer to the nearest WHOLE number) Part 3 Sodium chloride 3% is on backorder. How many milliliters of a 5% solution of boric acid (E value = 0.52) should be used in compounding the prescription? (Round the ο¬nal answer to the nearest WHOLE number) Part 4 If the pharmacist used 5% boric acid to adjust the tonicity of the solution, how many mL of puriο¬ed water should be used to prepare the order? PRACTICE 1. The pharmacist receives the following order: R Cocaine HCl Sterile water for injection qs 4% 25 mL The sodium chloride equivalent for cocaine hydrochloride is 0.16. How many milligrams of sodium chloride would be used to make this solution isotonic? (Round to the nearest WHOLE number) 9 0.22s Is xigxo.io onegnace 0.065race 1655rad How many milliliters of 3% NaCl should be used to prepare this order? (Round to the nearest TENTH) 0 59 300 2.167mi 12.2Mt 2. The pharmacy receives the following order: R Tetracaine HCl Zinc sulfate Boric acid Sterile water ad Make isotonic solution Sig. Instill 1 drop in each eye 0.2 g 0.1 g qs 60 mL How many milliliters of 10% boric acid solution should be used to prepare this order? The E values of tetracaine, zinc sulfate and boric acid are 0.18, 0.16, and 0.52 respectively. (Round to the nearest TENTH) oh GÉYaBa T.o.agxo.is oozognace z o.igxo.ie o.oiegn.ee 98 8 gg I.am 3. Lidocaine hydrochloride (MW = 289) is a 2-ion electrolyte. Calculate its sodium chloride equivalent. (Round to the nearest TENTH) ce E crosscuts C5B.s Csis.SC casaX 10.202 1 4. A pharmacist receives an order for 100 mL of procaine hydrochloride 1% solution for injection. Procaine HCl dissociates into 2 ions and has a molecular weight of 273. How many milligrams of NaCl are needed to make this solution isotonic? (Round to the nearest WHOLE number) to EE E o.ua sxig o.amasgnac oagnace o.aiuaisgnace o.ess7gnace Tale How many milliliters of 3% sodium chloride need to be added to make this solution isotonic? (Round to the nearest WHOLE number) 0.615579 58 HDMI How many mL of 5% boric acid (E value = 0.52) needs to be added to make this solution isotonic? (Round to the nearest TENTH) 0.61557g Nall 0.52 BA 1.318g go IET 5. How many milligrams of sodium chloride may be used in the preparation of 15 mL of an eye drop containing 1% tropicamide (E value - 0.09) and 0.5% chlorobutanol (E value 0.24) to render the solution isotonic with tears? Round to the nearest TENTH. o.issgnac xx to.is xo.su o.oasg xo.ua o.oissguaceo.usrace Is o.iossgnac i ios.sngn.ee ISOTONICITY key CALCULATING E VALUE Number of dissociated ions Dissociation factor (i) 1 1 2 1.8 3 2.6 4 3.4 5 4.2 (58.5) π E value = (ππ ππ πππ’π) (1.8) E value tells you how many grams of NaCl equivalents there are in 1 g of drug Ex: Boric acid has an E value of 0.52 This means there are 0.52 g of NaCl equivalents per 1 g of boric acid. This also means there are 0.52 mg of NaCl equivalents per 1 mg of boric acid. 0.52 π πππΆπ 1 π πππππ ππππ E value is a conversion factor used to convert g NaCl ↔ g drug β β You need an E value for every ingredient in your order that is not water or NaCl. You also need an E value if your isotonicity agent (i.e. what you are adding to make the solution isotonic) is not sodium chloride 1. Calculate the E value for ephedrine sulfate (MW = 429), which dissociates into 3 ions. (Round the ο¬nal answer to the nearest TENTH) 0.2 STEPS TO COMPLETING ISOTONICITY PROBLEMS 1. Calculate the necessary E values. If you already have them, skip this step. (E) 2. Calculate the total amount of NaCl needed to make the product isotonic. (Goal: Vol, NS) d. Pretend your volume of product = volume of NS. e. How many g of NaCl are in that volume of NS? f. Find out by multiplying your desired volume by 0.9 g NaCl/100 mL. This is how many total grams of NaCl are needed to make your product isotonic. 3. Calculate the total amount of NaCl equivalent contributed by each ingredient. (Have: gdrug x E) c. Multiply the total amount of each drug/ingredient (in grams) by the E value of the drug. This is how many g NaCl are being contributed by the ingredient d. If there are multiple ingredients, repeat for each ingredient and then add up the total amount of NaCl equivalents. 4. Find the amount of NaCl that needs to be added to make the product isotonic. (g NaCl Needed = G - H) a. Subtract Goal - Have to ο¬nd how many grams of NaCl should be added to make the product isotonic. (Need = Goal - Have) 5. Any other conversions you may need to do. (Ask) a. Ex: i. If they are asking for mg of NaCl, convert g NaCl from step 4 to mg ii. If you are asked for mL of 3% NaCl, convert g NaCl from step 4 to mL 3% NaCl iii. If you are asked for g of an isotonicity agent that is NOT NaCl (common ones include boric acid and zinc chloride), use the E value of the isotonicity agent to convert g NaCl from step 4 → g of the agent (i.e. divide by the E value) For example, if you were to use zinc chloride (E value = 0.62) to adjust tonicity, you would divide by 0.62. SAMPLE PROBLEM: Part 1 A pharmacist receives the following order: Ephedrine sulfate 0.3 g Sodium chloride qs Puriο¬ed water ad 30 mL Make isotonic solution Sig. Use as directed If the E value of ephedrine sulfate is 0.2, how many milligrams of sodium chloride should be used in compounding the prescription? (Round the ο¬nal answer to the nearest WHOLE number) 1. Calculate the necessary E values Given, E = 0.2 2. Calculate the total amount of NaCl needed to make the product isotonic. 0.27 g NaCl 3. Calculate the total amount of NaCl equivalent contributed by each ingredient. 0.06 g NaCl 4. Find the amount of NaCl that needs to be added to make the product isotonic. 0.21 g = 210 mg Part 2 Suppose the pharmacist will use 3% sodium chloride to adjust the tonicity in the above scenario. How many mL of 3% sodium chloride should be added to the product? (Round the ο¬nal answer to the nearest WHOLE number) 7 mL Part 3 Sodium chloride 3% is on backorder. How many milliliters of a 5% solution of boric acid (E value = 0.52) should be used in compounding the prescription? (Round the ο¬nal answer to the nearest WHOLE number) 8 mL Part 4 If the pharmacist used 5% boric acid to adjust the tonicity of the solution, how many mL of puriο¬ed water should be used to prepare the order? 22 mL PRACTICE 1. The pharmacist receives the following order: R Cocaine HCl Sterile water for injection qs 4% 25 mL The sodium chloride equivalent for cocaine hydrochloride is 0.16. How many milligrams of sodium chloride would be used to make this solution isotonic? (Round to the nearest WHOLE number) 65 mg Note: We got 70 mg because we rounded the total grams of NaCl needed to 0.23 g. If you keep the 0.225 g, and round at the end, you’ll get 65 mg. If you round to 0.23 g, you’ll get 70 mg How many milliliters of 3% NaCl should be used to prepare this order? (Round to the nearest TENTH) 2.2 mL Note: This is for 65 mg of NaCl. 2. The pharmacy receives the following order: R Tetracaine HCl Zinc sulfate Boric acid Sterile water ad Make isotonic solution Sig. Instill 1 drop in each eye 0.2 g 0.1 g qs 60 mL How many milliliters of 10% boric acid solution should be used to prepare this order? The E values of tetracaine, zinc sulfate and boric acid are 0.18, 0.16, and 0.52 respectively. (Round to the nearest TENTH) 9.4 mL 3. Lidocaine hydrochloride (MW = 289) is a 2-ion electrolyte. Calculate its sodium chloride equivalent. (Round to the nearest TENTH) 0.2 4. A pharmacist receives an order for 100 mL of procaine hydrochloride 1% solution for injection. Procaine HCl dissociates into 2 ions and has a molecular weight of 273. How many milligrams of NaCl are needed to make this solution isotonic? (Round to the nearest WHOLE number) 686 mg Hint: E value = 0.214 How many milliliters of 3% sodium chloride need to be added to make this solution isotonic? (Round to the nearest WHOLE number) 23 mL How many mL of 5% boric acid (E value = 0.52) needs to be added to make this solution isotonic? (Round to the nearest TENTH) 26.4 mL 5. How many milligrams of sodium chloride may be used in the preparation of 15 mL of an eye drop containing 1% tropicamide (E value - 0.09) and 0.5% chlorobutanol (E value 0.24) to render the solution isotonic with tears? Round to the nearest TENTH. 103.5 mg