SOLUTIONS

Question 1

Noyes Whiteny says to increase dissolution we must…

Answer 1

• Increase diffusion coefficient
• Increase SA
• Decrease drug conc in bulk solution
• Decrease boundary layer thickness

Question 2

How do we increase diffusion coefficient (in regards to Noyes)

Answer 2

• Diffusion is proportional to temp
• Inversely proportional viscosity and size

Question 3

How do we reduce boundary layer thickness

Answer 3

• Effected by flow and viscosity
• So use a stirrer

Question 4

Name the factors of the SOLUTE (drug) which effects its solubility

Answer 4

1. Chemical modification - functional groups
2. Crystal structure - test amorphous and crystalline forms
3. Using salt form/ change pH (to buffer)

Question 5

Name the factors of the SOLVENT (dissolving medium) which effects its solubility

Answer 5

• Use of co-solvent, solutes dissolve best in solvent with similar chemical properties
• Add surfactant: hydrophobic bit inside
• Temperature

Question 6

Define lipophicity

Answer 6

Affinity of a drug to a lipid environment

Question 7

A drug having lipophicity effects which other properties..

Answer 7

• Increases binding to enzymes/proteins
• Decreased aqueous solubility
• Increased absorption through membranes

Question 8

If a drug has a Log P value of 2, what does that tell us?

Answer 8

• Slighly lipophilic quickly passes through membranes

Question 9

Equation for Log P

Answer 9

[API] in octanol / [API] in aqueous

Question 10

Define colligative properties

Answer 10

When solute dissolves in a solvent its properties change

Question 11

Define hypertonic, hypo, and isotonic. Which one should a drug be

Answer 11

• 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

Question 12

What is salting in and salting out

Answer 12

• 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