PK2 - Formulation & Requirements of Parenteral Medicines 2

Tonicity

a measure of how a solution affects the volume of cells by changing their water content

Isotonic solutions

Preferred solutions with the same tonicity as body fluids

Hypotonic solutions

Solutions with lower tonicity than body fluids, can lead to RBC swelling and haemolysis

Hypertonic solutions

Solutions with higher tonicity than body fluids, can cause complications like dehydration and coma

Intraspinal/intrathecal injections

Require isotonic solutions to prevent adverse effects

Intradermal injections

Use isotonic solutions to avoid false positives

Intramuscular and subcutaneous injections

Prefer isotonic solutions, hypertonic solutions may enhance drug absorption

Total parenteral nutrition

IV infusion of a complete nutrition formula with high osmolarity

Preparation of isotonic solutions

Calculate osmolarity, adjust to match body fluids, add substances like NaCl to achieve isotonicity

Osmolarity method

Calculate osmolarity of components, adjust with substances like NaCl to reach isotonicity

Freezing point depression method

Use freezing point depression to determine isotonicity, adjust with substances like NaCl

Class I methods

Add NaCl or adjusting solute to reach freezing point of -0.52ºC for isotonicity

Class II methods - White-Vincent method

Add water to create isotonic solution, adjust volume with isotonic diluting vehicle

ΔTf

0.52

ΔTf NaCl

0.9%

Sodium chloride equivalent

the mass of NaCl that lowers the freezing point of a solvent to the same extent as 1g of the solute