Isotonic Solution

Question 1

Name the colligative properties of biological fluids

Answer 1

Colligative properties of Serum

• Osmotic pressure: 6.5 atm (0°C), 7.6 atm (37°C)
• Freezing point depression ΔTf: 0.52°C decreasing (below 0°C)

Water and electrolytes balance - Normally plasma contains

• (compare to the value from 0.9% NaCl)
• Electrolytes: ~155 mEq/L of cations and 155 mEq/L of anions.
• Osmolarity (serum) ~ 300 ± 10 mOsmol/L

Physiologic effects associated with increases in osmolility

Serum Osmolality(mOsmol/kg) Physiologic Changes
330 Fainting, central nervous system changes
320 Weakness
300 ± 10 Normal
250 Weakness
233 Seizures, coma

Question 2

What are isotonic solutions?

Answer 2

• Isotonic solutions produce no discomfort when instilled in the eye, nasal tract, blood, or other body tissues
• Isotonic solutions cause no swelling or contraction of the tissues with which they come in contact
• Physically and biologically: Isotonic solutions have the same osmotic pressure as that of the body fluids, with respect to a certain bio-membrane

Question 3

Describe an isotonic solution

Answer 3

Same # of impermeable solute particels per liter

Water in = water out

Usually freezing point equal -0.52C

Question 4

What is a hypertonic solution?

Answer 4

• Higher total impermeable solute particle concentration than cellular contents
• Freezing point lower than - 0.52  C
• Water flow out of cell, cause crenation (cell shrinkage)

Question 5

What is a hyptonic solution?

Answer 5

• Lower concentration of impermeable solute particle than cellular contents
• Usually, freezing point higher than - 0.52 C (- 0.52 ~ 0 C )
• Water flow into cell, hemolysis (cell swelling and bursting)

Question 6

Does isomotic and isotonic equal?

Answer 6

• Usually but not always equal

Osmotic pressure is related to an ideal semi-permeable membrane which only allow water to pass through

Isotonicity is related to the cell membrane permeability.

• Cell membrane may allow certain molecules to pass through, in addition to water
• If a solute can also diffuse freely across the cell membrane, it does not exert (contribute) tonicity properties with the membrane.
• e.g. NH4Cl , urea, alcohol, glycerin, and boric acid can cross the blood cell membrane, and should not be counted for isotonicity

Question 7

Isosmotic with blood, freezing point -0.52 C

Hyptonic with blood –> boric acid can pass through the erythrocyte freely and cause rapid hemolysis

Isotonic with lacrimal fluid –>Boric acid cannot past through eye mucous lining

Question 8

What are the two methods to adjust tonicity?

Answer 8

Class I method

• Cryoscopic method (Freezing point depression)
• Sodium chloride equivalent method (E value)

Class II method

• White- Vincent method
• Sprowls method

Question 9

What is the cyroscopic method?

Answer 9

It is the freezing point depression method see sheet and power point for equation

Question 10

Describe the sodium chloride equivalent method (E value)

Answer 10

Sodium chloride equivalent value (E) by Mellen and Seltzer 1936 – “Tonicic equivalent”
The NaCl equivalent (E value) of a drug is the amount of NaCl that has the same tonicity effect as 1 g of the drug.

“WNaCl” = E  Wdrug
E = “WNaCl” / Wdrug

E, Liso, Tf 1% Values were determined experimentally and are available for calculation

Question 11

What is the E value?

Answer 11

See equation

Question 12

How to calculate using E values

Answer 12

1. Amount of NaCl equivalent to the amount of drug in solution

“WNaCl” = E x Wdrug
“WNaCl” = E · (amount of drug in solution) = X g

2.If the drug were not added, how much NaCl would be needed to make V(ml) of isotonic solution?

WNaCl = (0.9g /100ml) · V = Y g
V: Volume of solution in ml

3. How much NaCl is needed to render the solution isotonic :
   WNaCl = WNaCl – “WNaCl” = Y – X

Question 13

What are tonicity agents?

Answer 13

NaCl, NaNO3
Ringer’s solution (NaCl, KCl, CaCl2)
Dextrose
Mannitol
Propylene glycol
Glycerin
Drug!
All solutes that are impermeable

Question 14

What is the white-vincent method?

Answer 14

V = W  E  111.1 ml

V: the volume (ml) of isotonic solution can be prepared by dissolving only the drug in pure water
W: Weight (gram) of the solute
E: sodium chloride equivalent value of the solute
What is 111.1? ….

Question 15

What is a multi-component solution?

Answer 15

To prepare multi-component solution

V = [ (Wi  Ei)]  111.1

Question 16

What is the Sprowl’s method and prowl’s value?

Answer 16

Sprowl’s value—the volume of an isotonic solution that can be prepared by the addition of water to 0.3g of drug
When W = 0.3 g,
Sprowl’s value = V
= W  E  111.1 ml
= 0.3  E  111.1 ml

Question 17

SUMMARY

Answer 17

ISOTONIC SOLUTIONS: definitions, properties and exceptions
METHODS OF ADJUSTING TONICITY
Class I method
Cryoscopic method (Freezing point depression)
Sodium chloride equivalent method
Class II method
White-Vincent method
Sprowls value
Other calculations
E from Liso
E from Sprowls value