Lecture 13

Question 1

Solubility of substance?

Answer 1

Amount that goes into a solution when equilibrium is established between the solute in solution and the excess (undissolved) substance

Question 1

Solution process?

Answer 1

1. Drug molecule removed from its crystal
2. Cavity from the molecule is created in the solvent
3. Drug molecule inserts into this cavity

Question 2

Saturated solution?

Answer 2

Contains drug at the limit of its solubility

Question 3

Factors affecting drug solubility?

Answer 3

Temp, shape/SA/hydrophobicity of drug/pH/solubilising agents/crystal characteristics

Question 4

Effect of increasing temp on solubility?

Answer 4

Increases solubility (higher energy)

Question 5

Effect of increasing mp/bp on solubility?

Answer 5

Decreases solubility (stronger interactions)

Question 6

Effect of ionisation (extreme polarity) on solubility?

Answer 6

Increases solubility - causes increases hydrophilicity

Question 7

Why will drugs partition between solvents?

Answer 7

Due to difference in solubility in difference phases (across cell walls)

Question 8

What is log P (partition coefficient) a measure of?

Answer 8

Lipophilicity/hydrophilicity (unionised form of drug)

Question 9

What is log P?

Answer 9

Ratio of conc of drug in oil/hydrocarbon to conc of drug in water

Question 10

If log P greater than 0?

Answer 10

Drug is lipophilic

Question 11

If log P less than 0?

Answer 11

Drug is hydrophilic

Question 12

Structure of crystals?

Answer 12

Highly ordered arrays of molecules/atoms held together by non-covalent interactions

Question 13

Polymorphism?

Answer 13

Molecules arrange themselves in different ways in the crystal