Download Ratios

Ratios, Proportions, Percents
Ratios
Show the relationship between two entities.
apples to oranges
apples to total fruit
men to women
total people to women
medication to saline solution
medication to total amount
Can be written:
a
b
a:b
a to b
Most common used in pharmacy.
The strength is a measure of the concentration of the drug per solid unit or the
concentration of the drug in a solution.
Solids – tablets, ointments, creams, powders
Tablets and capsules - the ratio will always be the amount of
medication per one (meaning per one tablet), even though tablets
can be cut in half. (examples: 1000mg/tablet, 100 : 1,
1000mg/capsule)
Ointments, crams, powders – expressed in units per weight
(examples: 50mg per 10g, 15 : 1)
Liquids – “how much of the drug (in weight or volume) per volume of
liquid (mL) into which the drug is mixed”
(examples: 5mg : 1L, 15mL : 1L)
Example 1 from text:
“Dispense Demeclomycin 250mg tablet per dose. Pharmacy stocks 500mg
tablets.”
500mg
 this ratio represents what the pharmacy HAS
1tablet
250mg
 this ratio represents what you NEED
dose(? tablets )
The question is how many tablets are needed for the 250mg dose?
500mg
250mg

 called a "proportion", now solve for "x "
1tablet x tablets
500  x  250  1
500 x  250
500 x 250

500 500
x  0.5 tablet or 1/2 tablet
This can also be done using a conversion chain. The question rephrased is, “ A
drug comes in 500mg tablets. I need 250mg for 1 dose. How many tablets will it
take for that one dose?”
1tablet 250 mg

 0.5tablets / dose
1dose
500 mg
1
or tablet per dose
2
In this case I think the
proportion is easier. You will
need to know both ways.
Practice Problems 3.1 (21-25) Let’s discuss these.
21.
750mg tablet of clarithromycin
22.
10mg capsule of dicyclomine
23.
125mg of amoxicillin in 5mL
24.
300mg of ranitidine in 2mL
25.
20mg of diphenhydramine in 1g
Proportions
Two ratios that are equal to each other.
Different ways to express this type of relationship.
3 9

most common
8 24
Use cross multiplication or reducing to
3 9
::
check for equivalency.
8 24
3 : 8  9 : 24
3 : 8 :: 9 : 24
Parts of the proportion have names. In our example above:
3 and 24 are called the ______________________
8 and 9 are called the ______________________
Example of solving proportions:
“A patient needs 300mg of medication. The pharmacy stocks 250mg/5mL
strength.”
250mg 300mg

start with what you know, include units
5mL
x mL
250 x  5  300
250 x  1500
1500
250
x  6mL
x
include the units
If asked, show the answer is correct by multiplying the means,
multiplying the extremes, and showing they are the same.
Percents
Mean out of 100, per 100, for every 100.
What are the rules? What are the short cuts?
Percent to Fractions
15%
15.2%
0.05%
Fractions to Percents
1/8
0.5/100
220/100
Percents to Decimals
2%
216%
0.2%
Decimals to Percents
0.5
50
60.8
Discussion (p32 in your text)
SOMETHING YOU SHOULD KNOW
The percent is used most often to express the concentration of intravenous
(IV) solutions and topical medications (creams and ointments). This can also be
called a percent strength. It describes the amount of drug contained in a
specific volume (liquid or solid).
An IV solution containing 5% dextrose has 5g of dextrose for every 100mL of
solution. It could also be translated as 5g/100mL, 0.05, or5:100.
An ointment that contains 0.1% triamcinolone has 0.1g of triamcinolone for
every 100g of ointment. This translates to 0.1g/100mL, 0.001, or 0.1:100 as a
fraction, decimal, or ratio respectively.
Homework for Chapter 3: (remember, the calculator is to be used for checking,
not for doing the work)
Chapter 3 Quiz (in text), you are to do every odd problem.
1-5 (1st section) Copy the problem, change to a fraction, give
simplified fraction.
1-5 (2nd section) Copy the problem, change to a ratio using a colon
without changing the numbers, simplify if possible.
1-5 (3rd section) Copy the problem, change to a ratio without
changing the numbers, give the simplified ratio if possible
1-5 (4th section) Copy the problem, change to a fraction or decimal,
then change to a percent (show any work you can’t do in your head).
1-5 (5th section) Copy the problem, change to a fraction or decimal,
change to a percent (show work)
1-5 (6th section) Copy the problem, change to a fraction (or decimal),
then give the simplified fraction (show any work you can’t do in your
head).
1-5 (7th section) Copy the problem, solve algebraically in a top down
manner. Each problem should have at least 3 lines (equations).
1-10 (last section, word problems) Answer each question by setting
up a proportion and solving in a top down manner. Units must be
included both in the problem and with the answer. Each answer
should be justified.