Math for the Pharmacy Technician: Concepts and Calculations

1. Math for the Pharmacy Technician: Concepts and Calculations Egler • Booth Chapter 10: Pediatric and Geriatric Considerations

2. Pediatric and Geriatric Considerations

3. Learning Objectives • Explain why dosages calculations for specific populations must be based on the individual patient. • Identify factors that affect the absorption, distribution, biotransformation, and elimination of drugs in special populations. • Determine safe doses for special population patients. When you have successfully completed Chapter 10, you will have mastered skills to be able to:

4. Learning Objectives(con’t) • Determine safe doses for special populations. • Calculate patient dosages based on body weight. • Calculate pediatric dosages using Clark’s Rule. • Calculate pediatric dosages using Young’s Rule.

5. Learning Objectives (con’t) • Find a patient’s body surface area (BSA). • Calculate patient dosages based on a patient’s BSA.

6. Introduction • Two special populations require extra consideration when calculating medication dosages • Pediatric (children under age 18) • Geriatric (mature adults over age 65) • Risk of harm is far greater due to way they break down and absorb medications

7. Introduction (con’t) • Clarify all confusing drug orders • Calculate with absolute accuracy • Verify that dose is safe • Seek assistance from your supervisor Do not take short cuts with medication calculations

8. Factors that Impact Dosing • Normal dose of medication makes assumptions • About the patient’s body and age • That body systems are fully developed and functioning • Special populations may need dosages adjusted due to this assumption not being true

9. Pharmacokinetics • Study of how drugs are used by the body • Absorption • Distribution • Biotransformation • Elimination Understanding these processes allows for adjustments for special populations

10. Absorption • Process that moves a drug from the site where it is given into the bloodstream • IV medications bypass the absorption process by going directly into the bloodstream • Oral medications absorbed in digestive system • Topical absorbed through the skin

11. Distribution • Process that moves the drug from the bloodstream to other body tissues and fluids • Target site is where the drug product produces its desired effect • Each drug affects drug target sites

12. Biotransformation • Process that chemically changes the drug in the body • Occurs primarily in the liver • Helps to protect the body from foreign chemicals including drugs

13. Elimination • Process where the drug leaves the body • Main way of eliminating is in the urine • Other ways • Air that we exhale • Sweat • Feces • Breast milk • Other body secretions

14. Drug Adjustment • Adjustment is needed if one of these four processes are not functioning within certain limits. • Dose adjustment is made according to nature and severity of patient’s condition. • You are not expected to make these adjustments, but be aware that they may have to be done.

15. Conditions That Impact Dosing Functions of body systems change over the life of a person Newborns – systems not developed yet • pH of stomach is lower • Thinner skin • Liver still developing • Less circulation to muscles

16. Conditions That Impact Dosing (con’t) Geriatrics – systems begin to deteriorate • Skin and veins become fragile • Decreased liver function • Decreased kidney function • Poor circulation

17. Working with Special Populations • Other Considerations • Parent or caretaker may be administering or assisting them with medications • These individuals will need education regarding any regular or special requirements

18. Teaching Patients or Caretaker About Medications • Name of the medication • Purpose • How to store it • How long patient needs to take the medication • How and when to take it • How to know if it is effective

19. Teaching Patients or Caretaker About Medications (con’t) • Required follow-up tests, doctor appointments • Possible side effects and what to do • Interactions with other drugs and foods • Symptoms to report to the doctor • What to do if a dose is missed • Keeping a list of all medications

20. Ensuring Safe Dosages • When you are working with special populations, always check the package insert, drug label, or product literature to ensure the safety of the dose to be administered. • Drug orders may be written in several ways. If you measure the medication, you have the responsibility to check whether the dose is the standard recommended dose.

21. Ensuring Safe Dosages (cont.) • The recommended dose is sometimes written as a range, with a minimum and a maximum recommended dose. In this case, you will need to determine if the dose ordered is not less than the minimum or greater than the maximum recommended dose.

22. Review and PracticeEnsuring Safe Dosages (con’t) Determine whether the following order is safe. If safe, calculate the amount to administer. Patient: Child who weighs 14.5 kg Ordered: Amoxil 75 mg PO q8h On hand: Usual child dose 20-40 mg/kg day q8h Answer: Dosage doesn’t fall within recommended dosage range; contact the physician.

23. CAUTION ! Convert ounces carefully. • The weight of babies is often measured in pounds and ounces. • Because 16 oz = 1 lb, an ounce is not a tenth of a pound. • A baby who weighs 8 lb 6 oz does not weigh 8.6 lb.

24. CAUTION! (con’t) Convert 6 ounces to pounds using as the conversion Thus, 8 lb 6 oz = 8.375 lb

25. Dosages Based on Body Weight Calculating dosage based on body weight: • Convert the patient’s weight to kilograms • Calculate the desired dose, D, by multiplying dose ordered by the weight in kilograms such as

26. Dosages Based on Body Weight (con’t) • Confirm whether or not the desired dose is safe by checking the label, package insert, or product literature. If unsafe, consult the physician who wrote the order • Calculate the amount to administer, using fraction proportion, ratio proportion, dimensional analysis, or the formula method

27. Review and PracticeDosages Based on Body Weight (con’t) Calculate the amount to administer to a three-year-old who weighs 34 lb. Ordered: hysocyamine sulfate 5 mcg/kg subq 1 h pre-anesthesia On hand: hysocyamine sulfate 0.5 mg/mL Answer: 0.15 mL

28. Pediatric Specific Dosage Calculations • There are two other forms of calculations used to calculate pediatric doses, Clark’s Rule and Young’s Rule. • Clark’s Rule uses the weight of the child to determine the desired dose and • Young’s Rule uses the age of the child to determine the desired dose.

29. Pediatric Specific Dosage Calculations (con’t) • Memory Tip • Young = age; the word “young” refers to the age of an individual, and Young’s Rule uses the age of the child to determine the desired dose.

30. Pediatric Specific Dosage Calculations (con’t) • Clark’s Rule for children’s dosage calculations uses the following formula:

31. Review and PracticePediatric Specific Dosage Calculations (con’t) Using Clark’s Rule, find the amount to be dispensed. The patient is a 6-year-old child who weighs 50 lb; the average adult dose is 250 mg.

32. Pediatric Specific Dosage Calculations (con’t) • Young’s Rule for children’s dosage calculations uses the following formula. (this formula can be used only if the child is a least 1 year of age):

33. Review and PracticePediatric Specific Dosage Calculations (con’t) Using Young’s Rule, find the amount to be dispensed. The patient is a 6-year-old child who weighs 50 lb; the average adult dose is 250 mg.

34. Dosages Basedon Body Surface Area (BSA) • BSA calculations are used to provide more accurate dosage calculations specific to the patient’s size and severity of his/her illness. • Some medications are based on patient’s body weight only. • Both weight and height are used to determine a patient’s body surface.

35. Calculating BSA Using a Formula • A patient’s BSA is stated in square meters or m2 • To calculate the BSA you must know the height and weight • Use a formula or a special chart called a nomogram

36. Calculating BSA Using a Formula To determine a patient’s Body Surface Area (BSA): 1. If you know the height in cm and weight in kg, calculate

37. Calculating BSA Using a Formula (con’t) 2. If you know the height in inches and weight in pounds, calculate

38. Review and PracticeCalculating BSA Using a Formula (con’t) Find the body surface area for an adult who is 5’6” tall and who weighs 168 lb. BSA = 1.9 m2

39. Calculating the Body Surface Area (BSA) using a Nomogram • Using a straight edge, align the straight edge so it intersects at the height and weight • Doing so will create an intersection in the BSA scale

40. Review and PracticeCalculating the BSA using a Nomogram (con’t) Find the body surface for a baby who is 24 in and weighs 14 lb and 8 oz Use the “Child’s Nomogram” BSA = 0.21 m2

41. Calculating Dosage Based on BSA Calculating dosage based on BSA: 1. Calculate the patient’s BSA. 2. Calculate the desired dose: dosage ordered x BSA = desired dose 3. Confirm whether or not the desired dose is safe. If unsafe, consult the physician who wrote the order. 4. Calculate the amount to administer, using fraction proportions, ratio proportions, or the formula method.

42. Review and Practice Calculating Dosage Based on BSA (con’t) Ordered: Ceenu (1st dose) 140 mg now for a child whose height is 38 in and weight is 47 lb According to the package the first dose is a single oral dose providing 130 mg/m2 The dose ordered 140 mg is above the first recommended dose. Contact the physician.

43. Review and Practice True or False A baby who weighs 6 lb 8 oz weighs 6.8 lb. Answer: False

44. Review and Practice True or False A baby who weighs 9.5 lb weighs 9 lb 8 oz. Answer: True

45. Review and Practice What two things are pediatric dosages often based on? Answer: Weight and BSA

46. Pediatric and Geriatric Calculations No matter how rushed you may feel, you cannot take shortcuts with any medication calculations, especially patients from special populations. THE END