1. Introduction to Clinical Pharmacology Chapter 3 Making Drug Dosing Safer

2. Multiple Check System
1 in 10,000 hospital deaths each year are a result of mistakes made calculating drug dosages.
Order entry, bar coding, and technological checks
Best method: manual redundancy system and the “5 rights and 3 checks” method
Nurses are the last line of defense for patients when it comes to drug calculation errors

3. Drug Label Information
Need drug, form, and dosage strength on the drug label
Review the MAR
Trade name = brand name; generic name = official drug name
Unit dose method

5. Use of Zero
Always use a zero before decimal points in drug dosages so the dosage is not incorrectly read
.25 mg could be misread as 25 mg, rather than mg

6. Review of Arithmetic: Fractions
Fractions: consist of a numerator and a denominator
Adding proper fraction with like denominators and unlike denominators

7. Review of Arithmetic: Fractions (cont.)
Comparing fractions
Multiplying fractions
Multiplying whole numbers and fractions
Multiplying mixed numbers
Multiplying whole numbers and mixed numbers
Dividing fractions
Dividing fractions and mixed numbers

8. Review of Arithmetic: Ratios
Ratio: a way of expressing a part of a whole or the relation of one number to another

9. Review of Arithmetic: Percentages
A percent means a part per hundred
It can also be expressed as a fraction
Changing a fraction to a percentage
Changing a ratio to a percentage
Changing a percentage to a ratio

10. Review of Arithmetic: Proportions
A proportion is a method of expressing equality between two ratios
Used to find an unknown quantity
The first and last terms of the proportion are called the extremes
The second and third terms of the proportion are called the means

11. Review of Arithmetic: Decimals
A decimal is a fraction in which the denominator is 10 or some power of 10
Parts of a decimal: number(s) to the left of the decimal, decimal, number(s) to the right of the decimal
Types of decimals
Reading decimals
Adding decimals
Subtracting decimals

12. Review of Arithmetic: Decimals (cont.)
Multiplying a whole number by a decimal
Multiplying a decimal by a decimal
Dividing decimals
Changing a fraction to a decimal
Changing a decimal to a fraction

13. Calculations of Drug Dosages: Systems of Measurement
Nurse must be familiar with calculations of all forms of drug dosages
Systems of measurement:
The metric system
The apothecary system
Household measurements
Conversion between systems
Conversion within a system

14. Calculations of Drug Dosages: Solutions
Solute is a substance dissolved in a solvent
Solutions are prepared by using a solid and a liquid, or a liquid and a liquid

15. Calculations of Drug Dosages: Reading Drug Labels
Drug labels give important information the nurse must use to obtain the correct dosage
Unit dose: a method of dispensing drugs in which each capsule or tablet is packaged separately
Drug labels contain two names: trade name, generic name
Dosage strength: the average strength given to a patient as one dose

16. Calculations of Drug Dosages: Oral Dosages of Drugs
Computed: physician not available, written in apothecary system and label in metric system
Tablets and capsules
(dose desired)/(dose in hand) = (dose administered)

17. Calculations of Drug Dosages: Parenteral Drug Dosage
Must be in liquid form before administered
Available in three forms
Parenteral drugs in disposable syringes or cartridges
Parenteral drugs in ampules and vials
Parenteral drugs in dry form

18. Calculations of Drug Dosages: Parenteral Drug Dosage (cont.)
Calculating intravenous flow rates
To allow IV fluid to infuse over a specified period, the IV flow rate must be determined
Methods of calculating intravenous flow rates
Method 1
Method 2
Method 3

19. Calculations of Drug Dosages: Parenteral Drug Dosage (cont.)
Oral or parenteral drug dosages based on weight
The dosage may be based on the patient’s weight
In many instances, references give the dosage based on the weight in kilograms rather than pounds

20. Dosage Calculations Using Dimensional Analysis
Procedure of calculating dosage using dimensional analysis:
Step 1: identify the unit of measure to be calculated
Step 2: write the identified unit of measure to be calculated, followed by an equal sign
Step 3: dosage strength is written, with the numerator always expressed in the same unit that was identified before the equal sign

21. Dosage Calculations Using Dimensional Analysis (cont.)
Procedure of calculating dosage using dimensional analysis (cont.):
Step 4: write the next fraction with the numerator having the same unit of measure as the denominator in the previous fraction
Step 5: the problem is solved by multiplication of the two fractions

22. Dosage Calculations Using Dimensional Analysis (cont.)
Procedure of metric conversion using dimensional analysis:
Step 1: write the unit of measure to be calculated, followed by an equal sign
Step 2: express the dosage strength as a fraction with the numerator having the same unit of measure as the number before the equal sign

23. Dosage Calculations Using Dimensional Analysis (cont.)
Procedure of metric conversion using dimensional analysis (cont.):
Step 3: write the next fraction with the numerator having the same unit of measure as the denominator in the previous fraction
Step 4: expand the equation by filling in the missing numbers using the appropriate equivalent
Step 5: solve the problem by multiplication

24. Dosage Calculations Using Dimensional Analysis: Temperatures
Two scales used:
Fahrenheit
Celsius