1 IanLarsonmonashedu Learning Objectives for these classes Define the term iso osmotic Define isotonic and differentiate from iso osmotic Explain the mechanism of action of hypertonic and hypotonic solutions on RBCs ID: 486568
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Slide1
Isotonicity 1
Ian.Larson@monash.eduSlide2
Learning Objectives for these classes*
Define the term ‘
iso
-osmotic’
Define isotonic and differentiate from
iso
-osmotic
Explain the mechanism of action of hypertonic and hypotonic solutions on RBCs
Explain what strategies are used to make hypertonic and hypotonic solutions isotonic
Define
osmolarity
and osmolality
Be able to use equations involving
C
iso
%
, FD
1%
, and
SCE.
Describe how one
can
measure
isotonicity
of biological fluids
*in
addition
to:
Before our next class you need to be able toSlide3
Before our next class you need to be able to*:
Define a) hypertonic, and b) hypotonic
Explain why a solution containing 2
mM
glucose (impermeable) and 2
mM boric acid (permeable) is hypotonic to a solution containing 3 mM sucrose (impermeable).Explain what happens to red blood cells when they are immersed in a hypotonic solution or a hypertonic solutionCalculate Ciso for each of the classes of L
* not all the answers are in these notes, you might need to look elsewhereSlide4
For more information
Martin, “Physical Pharmacy,” second half of Chapter 8, i.e., ignore the section on buffered solutions (
eg
in 4
th
Ed, read from p. 180 on)Florence and Attwood, “Physicochemical Principles of Pharmacy” Ed 4, pp 69-75Slide5
Questions and FeedbackSlide6
Some
preparations that may require tonicity adjustment.
Injections, particularly IM( intra-muscular), SC (subcutaneous) and large volume IV (intravenous) injections
Eye drops
Eye lotions
Bladder irrigationsNose dropsSlide7
A solution with a higher concentration of impermeable solutes compared to red blood cells is said to be:
hypotonic
A:
hypertonic
B:
isotonic
C:
iso-osmotic
D:Slide8
Solution A contains 2
mM
sucrose (impermeable) and 3
mM
of urea (permeable); while solution B contains 5
mM dextrose (impermeable)A:A is hypotonic to BB:A is hypertonic to B
C:
A is isotonic to B
D:
A is iso-osmotic to BSlide9
Under isotonic conditions
L
iso
for a new drug is 2.0, therefore
C
iso isA:0.9B:3.85
C:
1.04
D:
0.26Slide10
A higher than usual Packed Cell Volume result means the blood cells were placed in a
A
hypotonic solution
B
hypertonic solution
C
iso-osmotic solution
D
isotonic solutionSlide11
Hypotonic solutions
Group discussion (5 minutes)
What would happen to red blood cells if they were immersed in a hypotonic solution?Slide12
Preparation of Isotonic Solutions
Hypotonic
solutions are usually made isotonic with body fluids by adding some
therapeutically inactive solute
.
e.g., dextrose or NaCl for intravenous use boric acid or NaCl for ophthalmic use Hypertonic solutions are usually made isotonic with body fluids by dilution with water.Slide13
Conditions for isotonicity
Solutions which are
iso
-osmotic
with body fluids are only considered to be isotonic if :membranes are impermeable to the solute (urea, boric acid, hexamine can pass thru RBC membranes)the solute does not alter the permeability of membranes (ethanol, some anaesthetics, and propylene glycol can increase the permeability)no chemical reaction leads to a change in the total concentration of dissolved ions or molecules.Slide14
Ciso
Rearranging
C
iso
= 0.52/ Liso In general, Liso may be grouped as1.9 for non-electrolytes2.0 for weak electrolytes3.4 for uni-univalent electrolytes, eg NaClHigher values for electrolytes of higher valencySo if know L
iso for class of additive can calculate isotonic concentration
So from before
ΔT
f
=
Lc
So under isotonic conditions
ΔT
f
=
L
iso
c
isoSlide15
Ciso example
Calculate
C
iso
for
NaCl, dextrose and boric acid.Liso (NaCl) = 3.4, Liso (dextrose) = 1.9, Liso (boric acid)
Ciso
= 0.52/
L
iso
The isotonic concentration of
NaCl
is 0.15 M,
of
dextrose
is
0.27 M, and
of
boric acid
is
0.29
MSlide16
Calculation of isotonic composition from freezing point data
A 1% solution of sodium chloride in water has a measured freezing point depression of 0.576
º
C,
i.e
, FD1% = 0.576º CWhat is the percentage composition of NaCl required in an aqueous solution to be isotonic with serum?Ciso NaCl = (0.52 /
0.576) x 1% from 1%
NaCl
= 0.576 °C
=
0.90%.
Δ
T
f
(
iso
)
= 0.52
°
C
This
is the accepted value (w/v) of a sodium chloride solution that is isotonic to body fluids.
Slide17
example
A 1% solution of
atropine
sulfate
in water has a measured freezing point depression of 0.07º C.What is the percentage of atropine sulfate required in an aqueous solution to be isotonic with serum?Ciso atropine sulfate
= (0.52 /
0.07)
x 1%
= 7.4%
Slide18
example – multi-component formulations
You are asked to make a 3% morphine
sulfate
(
C
iso = 6.5%) isotonic by adding NaCl. How much NaCl do you need?CisoNaCl = 0.9%, %NaCl = ?