Flashcards in Solubility [Dr Green] Deck (15):
A liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent)
Define: Solvation (hydration)
Process of binding solvent to solute
Define: Drug dissolution
Spontaneous dissolving effected by:
Molecular structure of the solute
Additives' interactions with solvent and solute
List 5 factors which influence solubility
Boiling or melting point
Functional groups of solute
Crystal properties (electrolytes)
List 4 factors which impact on the rate of dissolution
Crystallinity (crystalline vs amorphous)
Why are acidic drugs less soluble in acidic solutions?
As the predominant unionised form cannot interact with water
Why are basic drugs more soluble in acidic solutions?
The ionic form is predominant so can interact with the water in the solution
Which forms of molecule exist in weak acids?
For weak acids, both ionised and unionised forms are present at equilibrium in the solution
Which form of molecule has a greater solubility - ionised or unionised?
How do buffers work in a solution?
Buffers stabilise pH and determine the degree of disassociation
What is the % ionised of a basic solution at a low and pHs?
100% ionised basic solution at low pH
0% ionised at high pH
What is the % ionised of an acidic solution at low and high pHs?
0% ionised at low pH
100% ionised at high pH
List 3 tactics to improve solubility
Co-solvency = altering polarity of solution
Salt forms and changing pH
Solubilisation = use of surfactant micelles to improve solubility
What is the purpose of cyclodextrins?
Hydrophobic inside and hydrophilic outside
Forms complexes with hydrophobic molecules
= improves solubility and bioavailability