METROLOGY andMeasurements

METROLOGY & Measurements

Define the common systems of measurement
Explain the process of percentage, ratio, and proportion and show how they apply to pharmacy calculations
Be able to solve practical problems using mathematical skills discussed in this talk
Program Objectives

It is the science of weights and measures.

new definition :metrology is the science of measurement that include all theoretical &practical aspects of measurements .
METROLOGY

it is a very broad field &may be divided in to three

subfields:
1-scientific or fundamental metrology: Concern the establishment of quantity systems &units of measurements.
2-applied metrology: Concern the application of measurements science to manufacturing &their use in society.
3-legal metrology : Concern measuring instruments for the protection of health ,environmental &public safety
METROLOGY


Tow types of systems of weights &measures are used :
1-old apothecaries system.
2-The classical metric system.
Types of systems

Science fields where precision is paramount

such as medicine, use a wide array of metrology instruments.
These instruments include surgical robots, drug delivery monitoring devices ,laser – based medical instruments ,computer assisted navigational systems, that use a four –dimensional positioning system to help surgeons perform complex operations
Medical metrology:

Used in writing prescriptions.

Used to specify the amounts of ingredients or quantity to be dispensed.
Used in the directions to the patient
Roman Numerals

ss = one-half

I = one
V = five
X = ten
L = fifty
C = one hundred
M = one thousand
Roman Numeral Symbols


Three Cardinal Rules:
#1 If a symbol follows another symbol of equal or greater value, the two symbols are added together
#2 If a symbol follows another symbol of lower value, the lower value is subtracted from the higher value
#3 First perform any necessary subtraction, then add the resulting values together to get the final answer
Roman Numerals

QUESTION 1: IX = ?

QUESTIION 2: CXXII= ?
QUESTION 3: 20 = ?
Roman Numerals

QUESTION 1: IX = 9

QUESTION 2: CXXII = 122
QUESTION 3: 20 = XX

H.W
QUESTION 1 : XCV=?
QUESTION 2: 60=?
QUESTION 3:LXXII=?
Roman Numerals


A ratio is the relation between like numbers
or values, or a way to express a fractional
part of a whole.
Ratios may be written:
As a fraction: 2/3
With the ratio or colon sign: 2:3
Using "per": 2 milliliters per 3 hours
(2ml/3hr)
Ratio and Proportion

The strength or concentration of various drugs can be expressed as a ratio. First, read the label of the drug and find the strength or concentration.
Express this strength as a ratio in fractional form,
as in the following examples:
Tolnaftate solution, 10 mg per ml = 10 mg/1 ml
Kanamycin injection, 1.0 gm/3 ml = 1.0 gm/3 ml
Isoproterenol inhalation, 1:200 = 1/200
Ratio and Proportion

Proportions will be your most used pharmacy calculation

Solve most dosage calculations
Numerous applications in everyday life
Used when two expressions are directly related to one another
For instance, if 1 kg of drug cost us $5, how much will
2 kg cost?
both expressions contain cost per weight if they are set up as ratios, once the problem is solved, both ratios should be equal
Ratio and Proportion


A proportion consists of two equal ratios and is essentially a statement of equality between two ratios.

Example

You have a 10-ml vial of aminophylline labeled "25 mg per ml"How many milliliters must be injected to administer a dose of 125 mg?

Ratio and Proportion

Example 1.
You have a 10-ml vial of aminophylline labeled "25 mg per ml".
How many milliliters must be injected to administer a dose of
125 mg?
Ratio and Proportion

Example

How many milliliters must be injected from an ampule of Prochlorperazine labeled "10 mg/2 ml" in order to administer a dose of 7.5 mg?
Ratio and Proportion



H.W
A formula calls for 42 capsules of 300mg of drug. How many milligrams would be required to make 24 capsules?


Ratio and Proportion

One person's error killed Elisha Crews Bryant,

hospital officials said:
“a miscalculation overdosed the pregnant 18-yearold with a magnesium sulfate meant to slow her labor. She got 16 grams when she should have gotten 4 grams. The young mother began having trouble breathing, went into cardiac arrest and could not be revived.”
Ratio and Proportion – RealLife

Patient received 16 gms Mag. Sulfate, fatal

dose.
Patient should have received 4 gms.
How many ML @ 25 gm/50 ml should she
have received?
Ratio and Proportion – RealLife

How many ML @ 25 gm/50 ml should she have received to obtain 4 gms??

25 gm 4 gm
-------- = -----------
50 ml X ml
25gm X = 200 gm/ml
X = 8 ml


Three types of percentage preparations
• Percent weight-in-weight (wt/wt)
X Grams / 100 Grams
• Percent volume-in-volume (v/v)
X Milliliters / 100 Milliliters
• Percent weight-in-volume (wt/v)*
X Grams / 100 Milliliters
Most Common
Percentage Preparations

Example 1. How much Potassium Chloride

in grams is needed to prepare a 1 Liter solution of 3% KCl solution?
Answer: 3% = 3 grams / 100mls
1 Liter = 1000 mls
Next: 3 grams X grams
---------- = -----------
100 mls 1000 mls
Finally: x = 30 grams
Percentage Preparations

THREE SYSTEMS

1–Avoirdupois (household system): pound , ounce(Wt.) and teaspoon, tablespoon , fluid ounce, pint, quart, Gallon (Vol.)
2–Metric :gram (Wt.),Liter (Vol.)
3–Apothecary (rarely used) :grain, dram, bound, ounce (Wt.) and fluid dram, fluid ounce, pint, quart, Gallon (Vol.)
Systems of Measurement


CONVERSION FACTORS
Micro – one millionth
Milli – one thousandth
Centi – one hundredth
Deci – one tenth
Kilo – one thousand
Metric System

3 tsp = 1 tbsp

2 tbsp = 1 oz
16 oz = 1 pt
2 pt = 1 qt
4 qt = 1 G
16oz = 1 lb
Avoirdupois Conversion Factors

1 tsp = 5 ml

1 tbsp = 15 ml
1 oz = 30 ml (29.57ml)
1 G = 3840 ml(3784ml)


Conversion Factors Between Systems
1 g = 15.4 gr
1 gr = 60 mg (64.8mg)
1 kg = 2.2 lb
1 lb = 454 g
1 oz = 30 gm

6.3 oz = ? Ml

Arrange the units so they will cancel and solve
Value x Conversion Factor = Answer
6.3 oz x 30ml = 189 ml
1oz
The units of ounces cancel, and you are left with milliliters
Conversions

Try This One

1.3 kg = ? grams
Value x Conversion Factor x Conversion Factor = Answer
1.3 kg x 2.2 lb x 454g = 1,298g
1kg 1lb
Or
Approximatley 1,300 gm


H.W
You receive a prescription for Cefzil 250mg/5mls with directions to take 1 teaspoonful by mouth twice daily for 10
days.
How much drug in milligrams, is in one teaspoonful? How much Cefzil in milliliters do you have to give the patient to last the full 10 days?
Conversion

Parenteral calculations deal with administration of IV fluids

Two main concepts you will learn
- Flow Rate
- Dose per Time
Parenteral (IV) Calculations

Flow rate is the speed at which an IV solution is delivered

Function of Volume per Time
- usually reported in milliliters per hour
The magical formula
volume ÷ time = flow rate
Note: Always be sure which time and volume units you are being asked to solve for Is it ml/min ? Or l/hr? Something else?
Flow Rate Calculations

A patient receives 1 L of IV solution over a 3 hour period. Calculate the flow rate in ml/hr.
Note: the volume given is in liters, but the answer asks for milliliters.
If the conversion wasn’t so obvious, we would first need to do a conversion of L ml.
volume ÷ time = flow rate
1000 ml ÷ 3 hours = 333 ml/hr
Flow Rate Calculations


A patient receives 0.75L of IV solution over a 4 hour period.
Calculate the flow rate in ml/hr
Another Rate Problem



A patient receives 0.75L of IV solution over a 4 hour period. Calculate the flow rate in ml/hr
0.75 L x 1000ml = 750ml
1 1L

750 ml ÷ 4 hours = 188 ml/hr

Another Rate Problem

By manipulating the rate formula, we can

solve for time
The equation becomes:
volume ÷ rate = time
Solve for Time

If an IV is run at 125ml/hr, how long

will 1 L last?
If an IV is run at 125ml/hr, how long will 1 L last?
volume ÷ rate = time
1000 ml = 8 hours
125ml/hr
Milliliters cancel and you are left with the units of hours
Solve for Time