Y khoa - Dược - Chapter 9: Special preparations and calculations

Math for the Pharmacy Technician: Concepts and CalculationsChapter 9: Special Preparations and CalculationsEgler • BoothSpecial Preparations and Calculations2Learning ObjectivesDetermine the percentages of solutions, dilutions, and solids.Prepare solutions from a concentrate.Prepare a compound.Measure insulin doses accurately.When you have successfully completed Chapter 9, you will have mastered skills to be able to:3IntroductionYou may be required to have additional knowledge related to dosage calculationsThis special knowledge will require specialized calculations Preparation of solutionsAlligations Insulin4Compounds When two or more chemicals are mixed together to make a specific mixture or solution, it is known as a compound in the pharmacy industry.It is occasionally necessary to prepare a solution “from scratch,” dilute a solution that is more concentrated than what is needed, or mix two solids together. 5Preparation of Solutions, Dilutions, and SolidsSolutions are liquid mixtures containing 2 or more chemicals.Solvent – used to dissolve other chemicals.Solutes – chemicals dissolved in the solvent.Common solvent is water.Universal solventNormal saline = 0.9% sodium chloride in every 100 mL of solution.6Preparation of Solutions, Dilutions, and Solids (cont.)Common examples of manufacturer solutions.InjectionsEye dropsCough syrupsYou may have to prepare a solution “from scratch”. 7Final Volume/Final StrengthAs a pharmacy technician you may have to find the final volume, initial volume, initial strength, or final strength of a mixture. To find the missing value you can use either the ratio proportion method or the fractional proportion method.As you work through this chapter, both methods are used to solve for final volume/final strength. 8Final Volume/Final Strength (con’t)Set up the equation for ratio proportion method as: Final volume : initial volume : : initial strength : final strengthSet up the equation for the fraction proportion method as: 9Percentage ConcentrationsCommon way to express concentrations is in percentages.Percent means “per hundred.”How much solute is found in every 100 mL of solution?10Percentage Concentrations (con’t)Solid solute % = grams of the solute in 100 mL 2% lidocaine = contains 2 g of lidocaine in every 100 mL of solutionLiquid solute% = milliliters of the solute in 100 mL70% isopropyl alcohol has 70 mL of isopropyl alcohol in every 100 mL solution11Percentage Concentrations (con’t)Solid solute and solid solvent% = grams of the solute in 100 g of the product2% hydrocortisone ointment means that 100 g of ointment will contain 2 g of hydrocortisone12Preparing % Solutions and SolidsYou must first measure the soluteThen add sufficient quantity of solvent to bring the total to desired volume13Review and PracticePreparing % Solutions and Solids (con’t)A “recipe” for preparing 100 mL of 2% lidocaine solution would look like this:*qsad = “sufficient quantity to adjust the dimensions to”2% Lidocaine Solution *qsad 100 mLWater2 gLidocaine14Review and PracticePreparing % Solutions and Solids (con’t)Write the recipe for preparing 100 g of 10% zinc oxide powder and petroleum jelly.90 gPetroleum jelly 10 gZinc oxide 10% zinc oxide15Preparing a Dilution from a ConcentrateYou may need to prepare a solution from a concentrated solution that is already prepared.Alligation method Use of formula16Preparing a Dilution from a Concentrate (con’t)To prepare a dilution from a concentrate, determine:Vn = the volume neededCn = the concentration neededCa = the concentration(s) available* * If water is being used, one of the these concentrations is zero.Then use the alligation method or formula to obtain your answer17Alligation MethodWrite out a tic-tac-toe grid and fill in the following values.Find the total number of parts in the solution by adding the 2 values in the right column.18Alligation Method (con’t)Concentration of HIGHERconcentrated solutionParts of the HIGHER concentrated solution neededThe concentration neededConcentration of LESS concentrated solutionParts of the LESSconcentrated solution needed19Alligation Method (con’t)Find the volume of 1 part by dividing the total number of parts into the volume needed.Multiply the volume of 1 part (answer from Step 3) by the number in the top right of the grid. The result is the amount of the more concentrated solution needed.20Alligation Method (con’t)Add a sufficient quantity of the less concentrated solution to bring the final volume up to the desired volume.21Review and PracticeAlligation Method (con’t)How would you prepare 500 mL of 50% ethanol from 90% ethanol?Desired volume is 500 mL - you would dilute the 90% by adding water up to a final volume of 500 mL.22Preparing a Dilution from a Concentrate – Formula Method*1. Identify the following information: Cn = the concentration neededCa= the concentration availableVn = volume needed*The formula method can only be used when one of the solutions has a concentration of 0%, such as water.2. Solve for: Va = the volume available23Preparing a Dilution from a Concentrate – Formula Method (cont.)Plug the values into the following formula:Cancel unitsSolve for the equation for Vn24Review and PracticePreparing a Dilution from a Concentrate – Formula MethodHow would you prepare 500 mL of 50% ethanol from 90% ethanol?Answer: 278 mL of 90% ethanol solution is needed to prepare 500 mL of a 50% solution 50% Ethanolqsad 500 mLWater278 mL90% ethanol 25InsulinInsulin is a pancreatic hormone that stimulates glucose metabolism.People who have low or no insulin production may have insulin-dependent diabetes.They often need routine injections of insulin to keep their glucose (blood sugar) from rising to levels that could be life threatening.Rotate injection sites.Insulin is commonly supplied in a 10-mL vial. 26Insulin SyringesInsulin administration is different from other types of injections.The syringe measures the amount of insulin rather than a volume of solution.Must use special insulin syringes marked in units.27Insulin Syringes (con’t)Standard U-100 syringes hold up to 100 units per 1mL solution.Calibrated for every 2 units or some in each unit.Smaller syringes hold up to 50 units (0.5 mL of solution)30 units 28For more accurate measurements, use a 50-unit insulin syringe for insulin doses less than 50 units when available, and a U-30 insulin syringe for insulin doses less than 30 units of 100 units/mL of insulin if these syringes are available. Insulin Syringes (con’t)29Decide which syringe to use.Ordered: Humulin R 55 unitsAnswer – 100-unit syringe and fill it to between the 54 and 56 units lineReview and PracticeInsulin Syringes (con’t)30U-500 insulin is used for patients with highly elevated blood sugars.Insulin may be given by IV. Use tuberculin or standard syringe when U-500 or doses over 100 units are ordered.These doses will not fit in a 100-unit syringe.Insulin Syringes (con’t)31Insulin Syringes (con’t)When using U-500 or a dose of insulin over 100 units use a tuberculin or standard syringe.32Review and PracticeInsulin Syringes (con’t)Determine amount of insulin to give.Ordered: Humulin R U-500 insulin 80 unitsAdminister 0.16 mL in a tuberculin syringe33Special Preparations and CalculationsTHE ENDThese calculations, like all other calculations, require attention to detail and 100 percent accuracy; completing them successfully will help you step into your new career as a pharmacy technician. 34