Transcript Dosage

The Pharmacy Technician
FOUNDATIONS AND PRACTICES
Chapter 14
Dosage Calculations
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Dosage Calculation
• Determine which information presented is
•
•
actually applicable to the question
Always use the higher dosage amount
when performing dosage calculations on
prescriptions that have a range for the
dose
This will provide the most conservative
solution and ensure the most accurate
potential days supply
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.1
Drug label for Prozac®.
(Courtesy of Eli Lilly and Company.)
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.3
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.4
Drug label for EryPed Drops®.
(Reproduced with permission of Abbott Laboratories.)
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.5
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Quantity to Disperse
• Determine which information is necessary
• Know the common SIG codes to perform
dosage calculations
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.8
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.11
Drug label for diazepam.
(© Copyright Boehringer Ingelheim Roxane, Inc. and/or affiliated companies 2009. All
Rights Reserved.)
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.12
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.14
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Active Ingredient Calculations
• Typically calculated when preparing
•
•
•
compounded preparations
Determine which information is necessary
Use ratio/proportion equation with the
dose and strength
Units of measurement (mL, etc.) must be
the same
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.15
Drug label for Codeine Phosphate Oral Solution.
(© Copyright Boehringer Ingelheim Roxane, Inc. and/or affiliated companies 2009. All
Rights Reserved.)
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.17
Drug label for Fentanyl®.
(Courtesy of Baxter Health Care Corporation.)
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.18
Drug label for dexamethasone oral solution.
(© Copyright Boehringer Ingelheim Roxane, Inc. and/or affiliated companies 2009. All
Rights Reserved.)
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Calculating the Correct Days Supply
• The information required to solve this
equation is:
– Quantity dispensed
– Dose dispensed
– Dose frequency
• The days supply is equal to the total dose,
divided by the product of the dose and the
dose frequency
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.19
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.22
Drug label for Ceclor®.
(Courtesy of Eli Lilly and Company.)
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.24
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.25
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations
• What is the appropriate quantity to
•
dispense?
How many total doses are to be
dispensed?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the total amount of amoxicillin, in
•
mg, to be dispensed?
How many days should this prescription
last?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.26
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the appropriate quantity to
•
dispense?
How many total doses are to be
dispensed?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the total amount of
•
dexamethasone, in mg, to be dispensed?
How many days should this prescription
last?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.27
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the appropriate quantity to
•
dispense?
How many total doses are to be
dispensed?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the total amount of albuterol, in
•
mg, per inhalation?
How many days should this prescription
last?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.28 (continued)
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.28
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the appropriate quantity to
•
dispense?
How many total doses are to be
dispensed?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the total amount of
•
methylprednisolone, in mg, to be
dispensed in the pak?
How many days should this prescription
last?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the appropriate quantity to
•
dispense?
What is the maximum number of doses
available if 60 tablets are dispensed?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 14.29
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the appropriate quantity to
•
dispense?
What is the maximum number of doses
available if 60 tablets are dispensed?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Multiple Dosage Calculations (cont.)
• What is the maximum amount of
•
alprazolam, in mg, to be taken daily?
How many days could this prescription
last, if 60 tablets are dispensed?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Dosages for Pediatric Patients
• Three primary systems for determining
accurate pediatric doses:
– Fried’s Rule—calculates pediatric dosages
based on the child's age in months
– Young’s Rule—uses a formula based on the
child’s age expressed in years (rather than
months)
– Clark’s Rule—based on using the patient's
weight, expressed in pounds
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Fried’s Rule
• An infant, 15 months old and weighing 20
pounds, needs streptomycin sulfate, which
is usually administered to adults as 1 gm
(1,000 mg) in a daily IM injection. What is
the appropriate dosage for the infant?
– To calculate the pediatric dosage based on a
child’s age in months, simply use the formula
for Fried’s Rule.
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Fried’s Rule (cont.)
• Using the information provided, set up the
calculation as follows:
Pediatric dose
15 (age in months)

 1,000mg (adult dose)
150

15
 1,000
150
Pediatric dose
Pediatric dose = 0.1 x 1,000
Pediatric dose = 100 mg
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Fried’s Rule (cont.)
• So, according to Fried’s Rule, the pediatric
dosage appropriate for a 15-month-old
would be 100 mg.
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Young’s Rule
• Let’s reexamine Example 14.9 in light of
Young’s Rule, which uses the child’s age
in years. The age of a 15-month-old could
be expressed as 1.25 years, since the
child has lived for 12 months (1 year) + 3
months (1/4 or 0.25 of a year).
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Young’s Rule
• Using an age of 1.25 years and the
information provided in Example 14.9, set
up the calculation, using Young’s Rule, as
follows:
Pediatric dose

1.25 (age in years)
 1,000mg (adult dose)
13.25 (age of child + 12)
1.25

 1,000
13.25
Pediatric dose
Pediatric dose = 0.094 x 1,000
Pediatric dose = 94 mg
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Young’s Rule (cont.)
• So, according to Young’s Rule, the
pediatric dosage appropriate for a 15month-old would be 94 mg.
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Clark’s Rule
• Let’s reexamine Example 14.9 in light of
Clark’s Rule, which uses the child’s weight
in pounds.
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Clark’s Rule (cont.)
• Using a weight of 20 pounds and the
information provided in Example 14.9, set
up the calculation using Clark’s Rule as
follows:
Pediatric
20 (weight in pounds)
 1,000mg (adult dose)
dose 
150

20
 1,000mg
150
Pediatric dose
Pediatric dose = 0.133 x 1,000
Pediatric dose = 133 mg
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Clark’s Rule (cont.)
• So, according to Clark’s Rule, the pediatric
dosage appropriate for a 15-month-old
who weights 20 pounds would be 133 mg.
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Weight Conversions
• Pounds are converted to kilograms by
dividing by 2.2
– Example: If the infant weighs 20 pounds,
what is her weight in kg?
– 20 ÷ 2.2 = 9.09
– The infant weighs 9.09 kg
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Weight Conversions (cont.)
• Kilograms are converted to pounds by
multiplying by 2.2
– Example: If the infant weighs 8 Kg, what is his
weight in pounds?
– 8 x 2.2 = 17.6
– The infant weighs 17.6 pounds
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Mg/Kg/Day
• Most precise system of dosage
• Based on the number of milligrams
suggested per kilogram per day
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Practice
• A dose of 4mg/kg/day of Plaquenil® can
be recommended for certain children
suffering from lupus. What would be the
appropriate dosage for a patient weighing
47 kg?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Practice (cont.)
• The daily dose of Omnicef®, for children,
is 14 mg/kg, up to a maximum dose of 600
mg/day. What is the appropriate daily
dosage for a patient who weighs 98
pounds?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Practice (cont.)
• The recommended dosage of fluconazole
is 6 mg/kg on day one, followed by 3
mg/kg/day for oropharyngeal candidiasis.
What are the appropriate dosages for a
child weighing 30 kg?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Practice (cont.)
• A child who weighs 76 pounds is
prescribed the antibiotic cefaclor. It is
recommended that children receive 20
mg/kg/day in divided doses every 8 hours.
How many mg should the child take per
dose?
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.