Y khoa - Dược - Chapter 7: Oral medications and parenteral dosages

Math for the Pharmacy Technician: Concepts and CalculationsChapter 7: Oral Medications and Parenteral DosagesEgler • BoothOral Medications and Parenteral Dosages2Learning ObjectivesDistinguish between different types of oral medications.Recognize the types of solid oral medications that may not be altered by crushing or opening them. Calculate the amount of a parenteral medication to administer.When you have successfully completed Chapter 7, you will have mastered skills to be able to:3Learning Objectives (con’t)Select the appropriate syringe.Correctly reconstitute powdered medications.Calculate the amount of reconstituted medications to administer.Accurately calculate doses of inhalant, rectal, and transdermal medications.Identify errors that occur in calculating and preparing parenteral doses.Calculate estimated days supply.4IntroductionYou will learn to apply the simple calculation methods learned in Chapter 6 to oral dosages, including solids and liquids.Follow the method of calculation that you have chosen by following the color coded examples.Remember that excellence is a must with dosage calculations.5Tablets and CapsulesSolid oral medications come in several forms:Tablets CapletsCapsules6TabletsMost common form of solid oral medications Combines with inactive ingredients Forms a solid disk or cylinderto be swallowedsublingualbuccalchewabledissolve in water7CapletsOval-shapedSpecial coating -- easier to swallowCaplet8CapsulesOval-shaped gelatin shells Contain medication in powder or granule formThe shell is usually two pieces that fit togetherThe shell can be separated to remove the medication when the patient cannot swallow a pill9GelcapsUsually a liquid medication in a gelatin shellNot designed to be opened10Scored TabletsScoring allows the tablet to be divided when smaller doses are orderedMost often, scored tablets divide into halvesSome divide into thirds or quartersMedication is evenly distributed throughout the tablet11Calculating Dosages for Tablets and CapsulesAlways question and/or verify when your calculation indicates to give a portion of a tablet when the tablet is not scored.Question and recheck any calculation that indicates that you should dispense more than three tablets or capsules.12Calculating Dosages for Tablets and Capsules (con’t)Follow these steps when determining the amount of medication to be dispensed to a patient:If necessary, convert the dosage ordered (O) to the desired dose (D) that has the same unit of measurement as the dose on hand (H).Calculate the amount to dispense by the method of your choice. 13Calculating Dosages for Tablets and Capsules (con’t)Follow these steps when determining the amount of medication to be dispensed to a patient:Recheck your calculation if necessary.3. Apply critical thinking skills to determine whether the amount you have calculated is reasonable. 14Review and PracticeThe order is to give the patient 15 mg codeine PO now.You have 30 mg tablets available.Calculate the correct amount of medication to give using one of the following methods.Fraction ProportionRatio ProportionDimensional AnalysisFormula Method15Fraction Proportion MethodCalculating the Amount to Dispense by Fraction Proportion:1. Set up the proportion as follows: dosage unit amount to dispense dose on hand desired dose2. Cancel units.3. Cross multiply, then solve for the unknown value.16Ratio Proportion MethodCalculating the Amount to Dispense by Ratio Proportion:The proportion will be set up as follows:dosage unit : dose on hand :: amount to dispense : desired dose Or Q : H :: A : D2. Cancel units.3. Multiply the means and extremes then solve for the missing value.17Dimensional Analysis MethodCalculating the Amount to Dispense by Dimensional Analysis:With dimensional analysis you will not need to calculate the desired dose and amount to dispense separately. You will place your unknown (amount to dispense) on one side of the equation then multiply a series of factors on the right side of the equation.Canceling units will help you determine the equation has been set up correctly.18Dimensional Analysis Method (con’t)Calculating the Amount to Dispense by Dimensional Analysis (con’t):Determine the units of measure for the answer and place it as the unknown on one side of the equation.On the right side of the equation, write a conversion factor with the units of measurement for the desired dose on top and the unit of measurement for the dose on hand.19Dimensional Analysis Method (con’t)Calculating the Amount to Dispense by Dimensional Analysis (con’t):Multiply the conversion factor by a second factor: the dosage unit over the dose on hand.Multiply by a third factor: dose ordered over the number one.Cancel units on the right side of the equation. The remaining unit of measure on the right side of the equation should match the unknown unit of measure on the left side of the equation.Solve the equation.20Formula MethodCalculating Amount to Dispense Using the FormulaMethod:1. Determine the desired dose. Determine the dose on hand (H) and dosage unit (Q)2. Fill the formulaD for the desired doseH for the dose on hand Q for the dosage unit in the formula A for the unknown or the amount to dispense 21Formula Method (con’t)Calculating Amount to Dispense Using theFormula Method (con’t):3. Cancel the units.4. Solve for the unknown.22Review and PracticeThe order is to give the patient 15 mg codeine PO now.You have 30 mg tablets available.Calculate the correct amount of medication to give using one of the following methods.Fraction ProportionRatio ProportionDimensional AnalysisFormula MethodAnswer: ½ tablet23Crushing Tablets or Opening CapsulesUses:Patients who have difficulty swallowing pillsPatients who have tube feedingsnasogastric tubesgastrostomy tubesjejunostomy tubesMay need physician order first Check the policy24Crushing Tablets or Opening Capsules (con’t)MixingCrush certain tablets.Open certain capsules.Mix with soft foods or liquids.Check for interactions between medication and the food or fluid.Example - Tetracycline is inactivated by milk and should not be given with antacids or vitamin and mineral supplements.25Crushing Tablets or Opening Capsules (con’t)Tube feedingsMust first dissolve the crushed tablet or opened capsule in a small amount of warm water. If medication cannot be crushed, see if an alternative form of the medication exists and ask the physician to order it that way.26Some Common Food and Drug InteractionsMedication:Mixed with:Causes:AntipsychoticsCoffee and teaReduces effectiveness of drugBronchodilatorsCaffeineStimulates the CNSCentral Nervous System (CNS) DepressantsBlack cohosh, ginseng, kava kava, St. John’s wort, valerian, ETOHIntensifies sedative effects of CNS depressant27Some Common Food and Drug Interactions (con’t)Medication:Mixed with:Causes:ErythromycinAcidic fruits or juices, carbonated beveragesDecreases antimicrobial activityFerrous sulfateTeaDecreased absorptionHaloperidolCoffee and teaDecreased absorption28Medication:Mixed with:Causes:InsulinCoffeeStimulated excretionMonoamine oxidase inhibitorsFoods containing tyramine such as hard cheeses, chocolate, red wine, and beef or chicken liverHeadache, nosebleed, chest pain, severe hypertensionSome Common Food and Drug Interactions (con’t)29Some Common Food and Drug Interactions (con’t)Medication:Mixed with:Causes:TetracyclinesDairy productsReduces effectiveness of drug30Crushing Tablets or Opening CapsulesTo prevent an incorrect dose of medication, do not crush or otherwise alter any of the following:Enteric-coated tabletsSustained-release forms of medicationAny tablet with a hard shell or coatingTablets for sublingual or buccal useCapsules with seals that prevent separating the two parts31Enteric-coated TabletsHave a coating that dissolves only in an alkaline environment such as the small intestineDeliver medication that would be destroyed by the stomach acid or that could injure the stomach lining32Enteric-coated Tablets (con’t)Often look like candies that have a soft center and a hard shellMust never be crushed, broken, or chewedMust be swallowed with their coating intact33Sustained-Release MedicationsAllows the drug to be released slowly into the bloodstream over a period of several hours.If the medication is scored, it may be broken at the scored line.Do not crush or dissolve. This would allow too much medication to be absorbed at one time.34SpansulesThese contain granules of medication with different coatings that delay release of some of the medication.You may open spansules and gently mix the granules in soft food, but do not crush or dissolve the granules.35Medications That Must Not Be Crushed or DissolvedNames that indicate sustained-release medications:-Bid LA Tempule-Dur CR ChronotabPlateau Cap XL RepetabSpan Sequel Tembid SA Spansule SR Extentab36Medications That Must Not Be Crushed or Dissolved (con’t)Names that indicate enteric-coated medications:ECEnseal37Reconstituting Liquid MedicationsReconstituting Liquid Medications:Use only the liquid specified on the drug label.Use the exact amount of liquid specified on the drug label.Check the label to determine whether the medication should be shaken before dispensing.38Reconstituting Liquid Medications (con’t)Reconstituting Liquid Medications:Check the label to determine whether the reconstituted medication must be refrigerated.Write on the label The date and time you reconstituted the medication.Your initials.Strength of reconstitution.39Reconstituting Liquid Medications (con’t)Reconstituting Liquid Medications:Check the label to determine how long the reconstituted medication may be stored.Discard any medication left after this time period has passed.40Reconstituting Liquid Medications (con’t)Reconstituting Liquid Medications: When medication can be reconstituted in different strengths, select the strength that will allow the desired dose in the smallest volume.41Reconstituting Liquid Medications (con’t)Reconstituting Liquid Medications:Read the order carefully when calculating the amount to dispense.The physician usually orders the dose in units of drug, not volume of liquid.Calculate the volume needed to dispense the desired dose.42Calculating the Volume of Liquid Oral Medication To calculate the volume of liquid oral medication to Dispense, use the same methods that you use for solid oral medications: fraction proportions ratio proportionsformula dimensional analysis43Calculating the Volume of Liquid Oral Medication (con’t) Find the amount to Dispense.Ordered: Ventolin 5 mg PO nowOn hand: Ventolin syrup 2 mg per 5 mLUse the calculation method of choice.44Fraction Proportion MethodCalculating the Amount to Dispense by FractionProportion:1. Set up the proportion as follows: dosage unit amount to Dispense dose on hand desired dose2. Cancel units.3. Cross multiply, then solve for the unknown value.45Ratio Proportion MethodCalculating the Amount to Dispense by RatioProportion:The proportion will be set up as follows:dosage unit : dose on hand :: amount to Dispense : desired dose Or Q : H :: A : D2. Cancel units.3. Multiply the means and extremes then solve for the missing value.46Dimensional Analysis MethodCalculating the Amount to Dispense by Dimensional Analysis:With dimensional analysis you will not need to calculate the desired dose and amount to dispense separately. You will place your unknown (amount to dispense) on one side of the equation then multiply a series of factors on the right side of the equation.Canceling units will help you determine the equation has been set up correctly.47Dimensional Analysis MethodCalculating the Amount to Dispense by Dimensional Analysis (con’t):Determine the units of measure for the answer and place it as the unknown on one side of the equation.On the right side of the equation, write a conversion factor with the units of measurement for the desired dose on top and the unit of measurement for the dose on hand.Multiply the conversion factor by a second factor: the dosage unit over the dose on hand.48Dimensional Analysis MethodCalculating the Amount to Dispense by Dimensional Analysis (con’t):4. Multiply by a third factor: dose ordered over the number one.5. Cancel units on the right side of the equation. The remaining unit of measure on the right side of the equation should match the unknown unit of measure on the left side of the equation.6. Solve the equation.49Formula MethodCalculating Amount to Dispense Using theFormula Method:1. Determine the desired dose. Determine the dose on hand (H) and dosage unit (Q)2. Fill the formulaD for the desired doseH for the dose on hand Q for the dosage unit in the formula A for the unknown or the amount to dispense 50Formula Method (con’t)Calculating Amount to Dispense Using theFormula Method (con’t):3. Cancel the units.4. Solve for the unknown.51Patient Education: Liquid MedicationsRead the label to learn how to store the medication.Use the measuring device provided or a device purchased specifically to measure medications.Household teaspoons and tablespoons do not measure liquid accurately.52Patient Education: Liquid Medications (con’t)Do not store medication longer than the label indicates. Medication used after expiration date may have lost potency or its chemical composition may have changed.53Patient Education: Liquid Medications (con’t)Wash the measuring device with hot water and a dishwashing detergent after each use. Dry it thoroughly. Store it in a clean container such as a plastic sandwich bag.Keep liquid medication in its original container.Do not transfer it to other containers.54Parenteral DosagesParenteral route of administration; medications that are delivered outside of the digestive tract; most often refers to injections. The most common injection types used to deliver medications include:Intramuscular (IM)-Medication administered into a muscle by injection.Subcutaneous (Sub-Q)-Medication administered under the skin by injection.Intravenous (IV)-Medication delivered directly to the bloodstream through a vein.Intradermal (ID)-Medication administered between the layers of skin.55Parenteral Dosages (cont.)Injections are mixtures that contain the drug dissolved in an appropriate liquid. The dosage or solution strength on an injectable medication’s label indicates the amount of drug contained within a volume of solution. Dosage strength may be expressed in milligrams per milliliter, as a percent, or as a ratio. Once you have determined the amount to be administered to the patient, you must select the appropriate syringe.56Parenteral Dosages (con’t)Selecting a syringe1. If the amount of injection to administer is 1 mL or more, use a standard 3-mL syringe.2. If the amount of injection to administer is less than 1 mL but greater than or equal to 0.5 mL, use a 1-mL tuberculin syringe.3. If the amount of injection to administer is less than 0.5 mL, use a 0.5-mL tuberculin syringe.57Other Medication RoutesMedications may be given by a variety of routes besides oral and common parenteral routes. These routes are used for:inhalantsophthalmic and otic dropstopical and transdermal rectal and vaginal medications.58Other Medication Routes (con’t)Inhalant-medication administered directly to the lungs, usually through a metered-dose inhaler or nebulizer.Topical-medications are applied to the skin and include ointments, creams, and lotions.Transdermal-medications are administered through the skin, typically via a patch. 59Other Medication Routes (con’t)Ophthalmic medications are used for the eyes and Otic medications are used for ears. Both are usually given in liquid/drop form. Some ophthalmic medications are supplied in ointment form. 60Other Medication Routes (con’t)Rectal-medication administered through the rectum, usually a suppository.Vaginal-medication administered through the vagina, in suppository, cream or tablet form. 61Estimated Days SupplyAs a pharmacy technician you may need to determine the estimated days supply of a prescription, which is how long the medication will last the patient if taken correctly. 62Estimated Days Supply (cont.)To determine estimated days supply you will multiply amount of medication to dispense by days needed over the number of dosage units per day. Amount to dispense  63Review and PracticeTrue or FalseAny tablet can be broken in half to give to a patient.Answer: False64Review and PracticeTrue or False Enteric-coated tablets can be crushed to give to a patient.Answer: False65Review and PracticeWhich of the following foods are contraindicated to mix with tetracyclines? A. Water B. Orange juice C. Milk D. ApplesauceAnswer: C. Milk66Review and PracticeWhich of the following types of medications can be crushed for administration? A. Scored tablets B. Enteric-coated tablets C. Sustained-release tablets D. Sublingual tabletsAnswer: A. Scored tablets67Review and PracticeWhat preparation must be done before Dispensing medication through a nasogastric tube? A. Nothing special is needed. B. Mix the medication with applesauce. C. Mix the medication with warm water. D. Mix the medication with ice cream.Answer: C. Mix with warm water.68Oral Medications and Parenteral DosagesTHE ENDRemember that excellence is a must with dosage calculations.69