SOLUTIONS Flashcards
Noyes Whiteny says to increase dissolution we must…
- Increase diffusion coefficient
- Increase SA
- Decrease drug conc in bulk solution
- Decrease boundary layer thickness
How do we increase diffusion coefficient (in regards to Noyes)
- Diffusion is proportional to temp
- Inversely proportional viscosity and size
How do we reduce boundary layer thickness
- Effected by flow and viscosity
- So use a stirrer
Name the factors of the SOLUTE (drug) which effects its solubility
- Chemical modification - functional groups
- Crystal structure - test amorphous and crystalline forms
- Using salt form/ change pH (to buffer)
Name the factors of the SOLVENT (dissolving medium) which effects its solubility
- Use of co-solvent, solutes dissolve best in solvent with similar chemical properties
- Add surfactant: hydrophobic bit inside
- Temperature
Define lipophicity
Affinity of a drug to a lipid environment
A drug having lipophicity effects which other properties..
- Increases binding to enzymes/proteins
- Decreased aqueous solubility
- Increased absorption through membranes
If a drug has a Log P value of 2, what does that tell us?
- Slighly lipophilic quickly passes through membranes
Equation for Log P
[API] in octanol / [API] in aqueous
Define colligative properties
When solute dissolves in a solvent its properties change
Define hypertonic, hypo, and isotonic. Which one should a drug be
- Hyper - moves out
- Isotonic - some move in, some move out
- Hypo - moves in
Drug should be ISOTONIC, therefore we add salts and sugars to allow this as excipients
What is salting in and salting out
- Salting out: When a salt is added to an aqueous solution, the salt competes with solute for the water molecules = REDUCING THE SOLUTES SOLUBILITY
- Salting in: Some large anions/cations increase solubility by hydrotropism e.g. adding sodium benzoate to aqueous solution increase solubility of caffeine
- Ahydrotropeis a compound that solubilizes hydrophobic compounds in aqueous solutions