Lecture 13 - Absorption of Molecules Flashcards
3 stages of drug solubility
- drug molecule removed from crystal
- cavity from the molecule is created in the solvent
- drug molecule inserted into cavity
What does a solution being saturated mean?
when a solution contains a drug at the limit of its solubility at any given temp and pressure.
What happens when solubility limit of a solution is exceeded?
solid particles of solute may be present
How does temp. impact solubility?
higher temp. = higher energy
collisions are more energetic and more likely to work. Therefore temp. should increase solubility.
How does surface area impact solubility?
because of entropy, large surface area is energetically less favourable (more cavities have to from around smaller clumps of drug molecules), so smaller surface area is actually faster
How does drug polarity/structure impact solubility?
like dissolves like, depending on functional groups solubility in different solvents will differ. Ionisation increases water solubility because ions are polar and water is polar.
What increases polarity more, polar groups or ionised groups?
ionised groups
what is Log P?
the partition coefficient. It is a measure of lipophilicity/hydrophilicity. Only considers unionised.
How can log P be determined experimentally?
shake-flask experiment. Drug is shaken in flask (as name suggests) in water and oil. Concentration of drug in water and in oil will be measured.
if log P is greater than zero?
lipophilic
If log P is less than zero?
hydrophilic
What does aliphatic mean?
not attached directly to aromatic ring
Why would you convert log P to P via inverse log?
to find ratio of molecules in lipid phase compared to hydrophilic phase
3 types of solid?
ionic solids, molecular solids, molecular salts
What does polymorphism mean?
compounds can crystallise out of solution in different ways in different habits and depending on conditions of crystallisation. Different polymorphs are referred to as forms
