Solubility [Dr Green] Flashcards Preview

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Flashcards in Solubility [Dr Green] Deck (15):
1

Define: Solution

A liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent)

2

Define: Solvation (hydration)

Process of binding solvent to solute

3

Define: Drug dissolution

Spontaneous dissolving effected by:
Molecular structure of the solute
Additives' interactions with solvent and solute

4

List 5 factors which influence solubility

Surface area
Boiling or melting point
Functional groups of solute
Crystal properties (electrolytes)
pH

5

List 4 factors which impact on the rate of dissolution

Crystallinity (crystalline vs amorphous)
Particle size
Agitation
Temperature

6

Why are acidic drugs less soluble in acidic solutions?

As the predominant unionised form cannot interact with water

7

Why are basic drugs more soluble in acidic solutions?

The ionic form is predominant so can interact with the water in the solution

8

Which forms of molecule exist in weak acids?

For weak acids, both ionised and unionised forms are present at equilibrium in the solution

9

Which form of molecule has a greater solubility - ionised or unionised?

Ionised

10

How do buffers work in a solution?

Buffers stabilise pH and determine the degree of disassociation

11

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

12

What is the % ionised of an acidic solution at low and high pHs?

0% ionised at low pH
100% ionised at high pH

13

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

14

What is the purpose of cyclodextrins?

Hydrophobic inside and hydrophilic outside
Forms complexes with hydrophobic molecules
= improves solubility and bioavailability

15

List 4 techniques that scientists can use to improve a poorly soluble API

Polymorph screen = find crystalline forms of the API by crystallisation
Salt screen = makes salts of the API - find the one with the best properties
Make amorphous = by freeze drying or spray drying
Form a co-crystal = convert API from one crystalline form to another by crystallising it out of solution with an inactive molecule