Tonicity Notes

Osmotic pressure

Pi

The effective hydrostatic pressure created between two liquids separated by a semipermeable membrane due to osmosis

Tonicity

The effective osmolarity of a solution

Reflects the net effect of all solutes capable of exerting osmotic forces on a membrane

Hypertonic solution

The solution has a higher solute concentration than the cell does, so water moves out of the cell into the solution. This causes the cells to shrink and shrivel

Hypotonic solution

The solution has a lower solute concentration than the cell does. Since the cell has a higher solute concentration water moves into the cell. This causes the cells to burst.

Hemolysis

The cells burst

Due to hypotonic solution

Crenation

The cells shrink and shrivel

Due to hypertonic solutions

5 USP recognized tonicity agents

Dextrose

Glycerine

Mannitol

Potassium chloride

Sodium chloride

3 non USP recognized tonicity agents

Boric acid

Sodium nitrate

Sodium sulfate

Tonicity agent that cannot be used for all ROAs

Boric Acid

Can be used for ophthalmic, not intravenous

4 methods of adjusting tonicity

Freezing point depression method

Liso method

Sodium Chloride equivalent method

USP method

Freezing point of isotonic solutions

-0.52

Freezing point of hypotonic solutions

Greater than -0.52

Freezing point of hypertonic solutions

Less than -0.52

The least specific tonicity adjustment method

Liso

Type I method

Adjusts solute concentrations needed for isotonicity

Type II method

Adjusts solvent volume to reach isotonicity

The only tonicity adjustment method that does not require a tonicity agent

USP method