Introduction to Pharmaceutical Calculation

Pharmaceutical Calculation

• application of basic mathematical calculations to ensure safe and effective pharmaceutical and medication preparation.

• Accurate calculation of formulas and conversions are vital.

Application of Pharm Calc to Pharmacy Practice

• Dose calculation

• Temperature conversion

• Flow Rates

• Measurement conversion

Application of Pharm Calc to Pharmacy Practice

• Dilution

• Solution concentration

• Ingredient calculation for compounds

• Prescription quantity calculation

Importance of Pharmaceutical Calculation Skills

• Ensure accuracy• Ensure patient safety by providing correct

dose• May cause harm to patient if not done

properly• To avoid under-dosing• To avoid overdosing

Review of Basic Algebraic Functions

1. Addition

2. Subtraction

3. Multiplication

4. Division

Addition

• Component parts

Addends – two numbers that are added

Total – answer to an addition problem

- also called sum

Addition

• Addition Symbol: +

• Total or Sum Symbol: = or ________

Subtraction• The difference between two numbers• Component parts Difference – the answer to a subtraction

problem Minuend – upper number Subtrahend – lower number Ex: 702 - minuend

- 512 - subtrahend

190 – difference

Symbol : -

Multiplication

• “repeated addition”• Component parts Factors – numbers that are multiplied

together Product – result of multiplication

problem

• Symbol : x

Division• “separating into parts”• Prime number – number whose only

factors are one and itself• Component parts of division Dividend – number being divided Divisor – number that is being used to

divide Quotient – the answer to a division

problem

• Symbol: ÷ or / or

Division

• Expressed in several ways

Ex: 100 / 20 = 5

dividend divisor quotient

100 ÷ 20 = 5dividend divisor quotient

5 quotient

20 100 dividend

divisor

Practice Problems

• Mr. Haddad gave you a prescription for Metoprolol 50mg two times daily. Compute the total amount of Metoprolol (in mg) he will consume in 7 days.

Solution

Metoprolol 50mg

x 2 ( times per day)

100mg per day total

Then

100 mg per day

x 7 days

Answer: 700 mg per week of Metoprolol total

Practice problems

• Pharmacy technician Omar Syed was instructed to repackage 920 milliliters (mls) bottle of wound care solution into 8 bottles. How many milliliters of wound care solution will each bottle contain?

Solution

Divide the 920 mls solution bottle by 8 bottles

920ml ÷ 8 bottles = 115 mls per bottle

answer

Arabic and Roman Numerals

• Arabic numerals – used worldwide

Ex: 0,1,2,3,4,5,6,7,8 and 9

• Roman numerals – commonly used to denote quantities in pharmacy practice– Also commonly used in writing

prescriptions

Roman numerals

Symbol

ss I

V

X

L

C

D

M

Equivalent

½ or 0.5

1

5

10

50

100

500

1000

Roman numerals• Note: When a smaller Roman numeral is placed before

a larger Roman numeral, the smaller Roman numeral is subtracted from the larger Roman numeral.

When a smaller Roman numeral is placed after a large one, the value of smaller numeral is added to the larger.

Ex: IX = 9 ( 10 or X minus 1 or I) Ex: XXII = 22 ( 2 times 10 or XX plus 2 times 1 or II)

Practice exercise

Convert the following Roman numerals to Arabic numerals:

IV = _______ DCV = ______

LXXIII = ______ VII = ________

XXXVII= ______ MCCCXLII = ______

XCI = _______ CDLV = _______

QUESTIONS

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