How to get an A and grasp this
concept!
 Know the differences between osmosis and diffusion
 Know page 171 in your calculations book, backwards
and forward
 Instead of “plugging and chugging” actually
understand where the equations come from and what
they are giving you
 Understand why this concept is important. You WILL
see it again in other classes whether you realize it or
not (i.e. major drug classes revolve around this
concept, such as diuretics)
How to get an A and grasp this
concept!
 Understand the difference between hypertonic,
hypotonic, and isotonic and how it affects cells
 Remember to double check your work.
 An eraser costs 10 cents, a mistake can cost you millions
and your pharmacy license!
Basic Concept: Osmosis and
Diffusion
Basic Concept: Osmosis and
Diffusion
 Osmosis is the passage of WATER from an area of high
concentration to an area of low concentration through
a partially permeable membrane
 Diffusion is the passage of molecules from an area of
high concentration to an area of lower concentration
Basic Concept: Osmosis and
Diffusion
 In the previous example, osmosis occurs because the
membrane is NOT PERMEABLE to the sugar
molecules but is permeable to the water.
 If there was a completely permeable membrane, the
water would move to the left and the sugar molecules
would move to the right until EQUAL concentrations
of each were on both sides
Basic Concept: Osmotic Pressure
 The pressure required to prevent solvent from passing
through a semipermeable membrane from a region of
higher concentration of solute to a region of lower
concentration of solute.
Osmosis and Diffusion: Application
to real life
 What does all this have to do with pharmacy?
 Believe it or not, all cells are semi-permeable

Thus, they allow some stuff to pass while inhibiting others
from passing
 This occurs through various processes, such as active diffusion,
passive diffusion, etc.
 The concept we need to understand is that cells will
behave differently based on what solution they are in
because water can move by way of osmosis
Osmosis and Diffusion: Application
to real life
 Say we have a human cell that contains 10% (THIS IS A
CONCENTRATION) NaCl within its cell membrane.
 There are basically 3 different solutions we can place it
in
 There are solutions that are more concentrated
 There are solutions that are less concentrated
 There are solutions that are the same concentration
Osmosis and Diffusion: Application
to real life
 If we placed the cell in the previous slide in a solution
that contains the same concentration of NaCl then
there would be no net movement of water because the
cell is at “equlibrium”
 When this occurs, the solution is said to be isotonic
 Note that even though there is no net movement of
water, water still goes back and forth
Osmosis and Diffusion: Application
to real life
 What would happen if we placed a cell with 20% NaCl
in a solution that only had 10% NaCl?
Osmosis and Diffusion: Application
to real life
 In this situation, the cell is MORE CONCENTRATED
with solute particles than the solution (i.e. the outside
of the cell has more WATER per unit volume)
 Remember, water moves from an area of high
concentration to low concentration
 Thus, water will move into the cell
 This type of solution is called Hypotonic
Osmosis and Diffusion: Application
to real life
 What if the solution contained a higher concentration
of solute (NaCl)?
Application to life: One step further
 Instead of a regular cell, let’s see what would happen
with a red blood cell!
Application to life: One step further
 When a red blood cell is placed in an isotonic solution
nothing happens
 When a red blood cell is placed is a hypertonic
solution the cell begins to shrink as water goes out of
the cell, a process called CRENATION
 When a red blood cell is placed in a hypotonic solution
the cell begins to swell and burst, a process called lysis
(hemolysis)
One more step further
 Knowing what you know now, explain what would
happen in the following situations
 Applying 5% NaCl eyedrops to the eye given that the
“concentration” of the eye is 0.9%

Commercially available as Muro 128 ® eyedrops
 Swallowing mannitol which is a nonelectrolyte that
behaves like NaCl and is impermeable to the intestines
 Hold your pee for a Wii®!!!
Important Note
 Remember, osmotic pressure that is produced on
either side of a membrane is related to the number of
particles the solute produces, not just the
concentration.
 i.e. A cell placed in a 10% solution of KCl will behave
differently than a cell placed is a solution of 10% NaCl
because of Osmolarity of the different molecules

Explained in detail later
Basic Concept: Electrolyte vs.
Nonelectrolyte
 An electrolyte is a molecule that dissociates into solution
and conducts current due to a charge on the molecule
 Examples include NaCl, KCl, etc.
 When an electrolyte is placed in a solution, it produces 1
Osmol for every particle that dissociates (assuming 1
molecular weight)

NaCl Example
 A nonelectrolyte doesn’t dissociate when placed in solution
 Examples include Dextrose, Boric Acid, Mannitol
 When an electrolyte is placed in a solution, it only produces 1
Osmol (assuming 1 molecular weight)

Dextrose Example
Basic Concept: Molecular weight
and other measures
 The molecular weight and the "electrolyte status” of a
molecule gives us a bunch of information
 Know that 1 Osmol is the amount of a solute that will
provide 1 Avagadro’s Number of particles
 Based on this information, we can deduce that if we
have a solution of 1 molar dextrose and 1 molar NaCl
that the NaCl solution would have more particles
because it gives 2 Osmol per mole
Understanding the differences
between substances
 Suppose in the below diagram we had 58.5 g (1 mole)
of NaCl on the left side of the semi-permeable
membrane and on the right side we had 61.8 g (1 mole)
of Boric acid
 Which way would the water move? Why?
Understanding the differences
between substances
 With only knowing the fact that NaCl is an electrolyte
and Boric Acid is a nonelectrolyte and that we have 1
molecular weight of each we can tell that the NaCl side
would have more particles
 Thus, water would move into the NaCl compartment
Understanding the differences
between substances
 Suppose in the below diagram we had 10% NaCl on the
left side and 10% KCl on the right side (assume equal
volume of solution on each side)
 Which way would the water move?
Understanding the differences
between substances
 In the example, we have to take into consideration the
molecular weights and Osmolarity of the two
substances.
 The MW of NaCl is 58.5 g which provides 2 Osmol, thus
in a 10% solution we would only have 0.1709 moles or
0.3418 Osmol
 The MW of KCl is 75 g which provides 2 Osmol, thus in
a 10% solution we would only have 0.1333 moles or
0.2666 Osmol
 Based on this we can see that there would be more
particles on the NaCl side and thus water would move
into the NaCl compartment
Understanding the differences
between substances
 Suppose we had 0.1 molar solutions of two different
nonelectrolytes, say dextrose and boric acid, in the
below diagram
 Which way would water move?
Understanding the differences
between substances
 Because there are an equal number of moles of two
nonelectrolytes, and thus the same number of
particles, the net movement of water will be zero!
Homework!
 Look up NORMALITY and know how it would come
into play in the above scenarios (i.e. 1N NaCl on one
side and 1N KCl on one side)
A side note on particle number
 How many Osmol would 1 mole of CaCl2 provide in
solution?
What’s the purpose of all this?
 The whole idea is to be able to make a solution that
will either be isotonic, hypertonic, or hypotonic with
body fluids in order to get the effects we want.
 For example, if we want to give someone fluid to prevent
dehydration we want it to be isotonic with the blood so
we won’t hurt the red blood cells.

Or if we want to make someone have a bowel movement we
want to make the inside of the intestines Hypertonic so water
will come into the intestines and produce a bowel movement
Colligative properties
 Colligative properties are properties of solutions that
depend on the number of molecules in a given volume
of solvent and not on the properties (e.g. size or mass)
of the molecules
 There are 4 colligative properties: Boiling point,
Freezing point, Vapor Pressure, and Osmotic Pressure
 To understand how each of these behave, let’s talk about
salt.
Colligative properties continued
 Thus, when we add salt to a pot of water 4 things
happen:
 The vapor pressure goes down
 The osmotic pressure goes up
 The boiling points goes up
 The freezing point goes down
 To help you remember this, just keep in mind:
Colligative properties continued
 Of the properties, we will be using the freezing point
for class purposes
 When you add exactly 1 mole of a nonelectrolyte to
water it brings the freezing point down to -1.86 degrees
celcius
 What do you think would happen if we added 1 mole
of an electrolyte?
 Would it bring it down even further (depress it) or raise
it further?
Colligative properties continued
 If we add an electrolyte, it will depress it even further
depending on how much the molecule dissociates in
solution (i.e. creates more particles)
 This brings us to the concept of the “i value”

Is a proportionality constant that relates number of particles
to freezing point depression
 We determine this value based on the assumption that
electrolytes, with a few exceptions, dissociate at 80% in
solution
Colligative properties continued
 How to calculate NaCl Value
 How to calculate KCl Value
 How to calculate CaCl2 value
 Exceptions (Zinc Sulfate)
The body’s freezing point
 Based on the concentration of different solutes in our
blood and bodily fluids, it has been found that we will
freeze at -0.52 degrees Celsius
 Walt-Disney!
 If we know that a 1 molar solution of NaCl freezes at 1.8
* -1.86 degrees Celsius then we can determine what
molar solution of NaCl freezes at -0.52 degrees Celsius
 Thus, it will be isotonic with body fluids
Equation number 1!
o
Mole in gL-1.= - 1.86 C*i
o
XgL-1.
- 0.52 C
Standard Calculations
 Now we are able to calculate what percent solution of
different solutes are isotonic with bodily fluids
 NaCl
 Dextrose
 Boric Acid
 KNO3
Standard Calculations
 Note: There is a difference between something that is
isotonic and isoosmotic!
 Isoosmotic => Same number of Osmoles
 Isotonic=> Physiological compatability
Standard Calculations
 What’s the difference between 1 mole of NaCl and 1
mole of KCl?
 What’s the deal with Boric Acid?
 IS ISO-OSMOTIC WITH BOTH BLOOD & LACRIMAL
FLUID
Standard Calculations
 True or False: Everything that is isotonic is isoosmotic.
 True or False: Everything that is isoosmotic is isotonic.
Methods for making something
isotonic
 There are three different ways to calculate how to
make something isotonic
 The “D” Method, or depression method
 The “E” Method, or equivalent method
 The “V” Method, or volume method
The “D” Method
 You’re working in a compounding pharmacy when you receive the following
prescription from Dr. Saber Samaan:
Freezing Point “D”epression
Explaination
 With the D method, you are seeing how much each
drug required of the prescription depresses the
freezing point towards -0.52 degrees celsius. You will
then make up the difference with NaCl or whatever
other agent the prescription calls for to make it
isotonic!
Freezing Point “D”epression
 The first step is to calculate how much NaCl would be
needed to make the volume of the prescription
isotonic!
 It’s a simple proportion from the 0.9% reference we
already know

If 0.9 grams will make 100 mL isotonic, how many grams will
make 30 mL isotonic?
FREEZING POINT “
D”EPRESSION
Naphazoline HCl
-1
247gL
-1
0.2gL
o
= - 1.86 C*1.8
o
-X C
o
- 0.0027 C
FREEZING POINT “
D”EPRESSION
ZnSO4
-1
288gL
-1
2.5gL
o
= - 1.86 C*1.4
o
-X C
o
0.0226 C
Total depression
o
0.0027 C
o
+0.0226 C
0.0253
oC
o
= -0.52-(-0.0253) = 0.4947 C
270 mg
Xmg
o
0.52 C
o
0.4947 C
The “E”quivalent Method
 The “E” method is a littler different
 Here, we are basically seeing how much NaCl produces
the same osmotic effect as 1 gram of the drug!
 In essence, we are “converting” the drugs in the
prescription to its NaCl equivalent

In order to do so we have to take into account the drugs i value
and molecular weight
The “E”quivalent Method
 The first step here is the same as the first step in the D
method
The “E”quivalent Method
Mole of NaCl gL-1 * iDrug
Mole of drug gL-1 * iNaCl
The “E”quivalent Method
-1
58.5gL
*1.8
-1
247gL *1.8
= 0.2368 g NaCl
The “E”quivalent Method
 Knowing this, we must now set up a proportion
 If 1 gram of Naphazoline HCl is equal to 0.2368 grams of
NaCl, then 0.006 grams of Naphazoline is equal to X
grams of NaCl?
The “E”quivalent Method
-1
58.5gL *1.4
-1
288gL *1.8
= 0.1579
The “E”quivalent Method
 Knowing this, we must now set up a proportion
 If 1 gram of Zinc Sulfate is equal to 0.1579 grams of NaCl,
then 0.075 grams is equal to X grams of NaCl?
The “E”quivalent Method
 The next step is to sum up the two quantities
calculated and subtract them from step 1!
The “V”olume Method
 The V method relies on the E value and involves a lot
of proportions
 The purpose of this method is to determine how much
water the drug should be dissolved in and then the
excess volume of the prescription is made up with NSS
The “V”olume Method
-1
58.5gL
*1.8
-1
247gL *1.8
= 0.2368 g NaCl
100 mL
x mL
0.9gNaCl
0.2368gNaCl
x mL = 26.32mL
Dissolving 1 g of Naph.HCl in 26.32
mL of distilled water, the solution will
be isotonic.
26.32mL 1 g N.HCl
x mL
0.006 gN.HCl
If you dissolve 6 mg of
N.HCl in 0.16 of water,
the sol. will be isotonic.
0.15792 mL
The “V”olume Method
-1
58.5gL *1.4
-1
288gL *1.8
= 0.1579
100 mL
x mL
0.9gNaCl
0.1579gNaCl
x mL = 17.5mL
Dissolving 1 g of ZnSO4 in 17.5
mL of distilled water, the solution will
be isotonic.
17.5mL
x mL
1 g ZnSO4
0.075 g ZnSO4
1.31 mL
If you dissolve 75 mg of
ZnSO4 in 1.31 mL of H2O,
the sol. will be isotonic.
0.1579 mL
1.3125 mL
1.4704mL
Dissolve 6 mg of
naph.HCl & 75 mg
ZnSO4 in 1.47 mL
water, and qs to 30
mL with isotonic
0.9% NaCl.
*This is the easy part*
Electryoltes
 Na & Cl are the most plentiful electrolytes in the body
 NORMAL HEALTHY HUMAN:
 Na 138-146
mMol.L-1
 Cl 98-109
mMol.L-1
 K 3.7-5.3
mMol.L-1
 Ca 2.25-2.65 mMol.L-1
 *Memorize this table, it will prove useful on the test
and in other classes to come!
Osmoticity: Application to real life
 Believe it or not, the simplest things in life all relate to
everything we’ve been talking about
 Why do we become thirsty?
Signs and Symptoms of Osmoticity
Changes
 Normal 285 mOsmol kg-1 282-288 mOsmol kg-1
 THIRSTY 294-298 mOsmol kg-1
 DRY MUCOUS MEMBRANE:299-313 mOsmol kg-1
 WEAKNESS, DOUGHY SKIN: 314-329 mOsmol kg-1
 Once your plasma osmoticity >330 mOsmol/kg:
 Disorientation
 Orthasis
 Severe Weakness
 Fainting
 Coma
Signs and Symptoms of Osmoticity
Changes
 As your Osmoticity goes below normal range:
 Headache (275-261)
 Drowsiness (262-251)
 Cramps (250-233)
 Seizures & Coma (<230)
Compensation Mechanisms
 What mechanisms does our body have in place to
combat changes in plasma osmoticity?
 ADH
SERUM OSMOLALITY
1.86 Na + BLOOD SUGAR + BUN +5
18
2.8
A QUIKY
2 Na + BLOOD SUGAR + BUN
20
THE QUICKEST
2 Na + 10
3
Serum Osmoticity: Homework
 Look up the signs and symptoms of dehydration
Serum Osmoticity: Practical
Application
 A patient comes into your pharmacy stating that they
have been puking for the past couple of hours. They
state that the puking has subsided, but have an
extreme thirst as they had been playing basketball the
night before and didn’t drink anything afterwards. The
technician on duty suggests that the patient get some
Gatorade and drink it.
 Is this a good recommendation?
Serum Osmoticity: Practical
Application
 Although it may seem to be a good recommendation,
you must remember that Gatorade is loaded with
sugar. This has the potential to worsen the patients
dehydration.
A few more practical applications
 Lactulose (Cephulac)
 This drug is a nonabsorbable disaccharide that is given
by mouth to patients for two indications: Constipation
and Hepatic Encephalopathy


Hepatic Encephalopathy is caused by excess ammonia that
irritates the CNS due to the liver not being able to detoxify it
 When the normal flora try to break down lactulose, they
produce Lactic Acid. This creates an acidic medium that
ionizes NH3 and it is excreted instead of being absorbed
Also acts as an osmotic diuretic
A few more practical applications