Isotonicity PowerPoint Presentation, PPT - DocSlides

Isotonicity PowerPoint Presentation, PPT - DocSlides

2016-11-09 60K 60 0 0

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1. Ian.Larson@monash.edu. 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.edu

Slide2

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 to

Slide3

Before our next class you need to be able to*:

Define a) hypertonic, and b) hypotonicExplain 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 elsewhere

Slide4

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

69-75

Slide5

Questions and Feedback

Slide6

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 irrigations

Nose

drops

Slide7

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 B

B:

A is hypertonic to B

C:

A is isotonic to B

D:

A is iso-osmotic to B

Slide9

Under isotonic conditions Liso for a new drug is 2.0, therefore Ciso is

A:

0.9

B:

3.85

C:

1.04

D:

0.26

Slide10

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 solution

Slide11

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 Ciso = 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 valency

So if know Liso for class of additive can calculate isotonic concentration

So from before

ΔT

f

=

Lc

So under isotonic conditions

ΔT

f

=

L

iso

c

iso

Slide15

Ciso example

Calculate Ciso for NaCl, dextrose and boric acid.Liso (NaCl) = 3.4, Liso (dextrose) = 1.9, Liso (boric acid) Ciso = 0.52/ Liso The isotonic concentration of NaCl is 0.15 M, of dextrose is 0.27 M, and of boric acid is 0.29 M

Slide16

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% =

0.576

º

C

What

is the percentage composition of NaCl required in an aqueous solution to be isotonic with

serum?

C

iso

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

0.07

º C.

What

is the

percentage

of

atropine

sulfate

required in an aqueous solution to be isotonic with

serum?

C

iso

atropine

sulfate

=

(0.52 /

0.07)

x 1%

= 7.4%

Slide18

example – multi-component formulations

You are asked to make a 3% morphine sulfate (Ciso = 6.5%) isotonic by adding NaCl. How much NaCl do you need?

C

iso

NaCl = 0.9%, %NaCl = ?

Slide19

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