Solutions Part 1 Flashcards

1
Q

What are the similarities and differences between a solution and a suspension?

A
  • solution is a homogeneous phase while suspension is heterogeneous.
  • both solutions and suspensions comprise two or more components.
  • continuous phase can be aqueous or non-aqueous.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the various methods that can be employed to increase apparent solubility of compounds in an aqueous medium?

A
  • cosolvency
  • pH control
  • solubilisation
  • complexation
  • chemical modification
  • particle size control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What type of drug particles is used to increase apparent solubility of compounds in an aqueous medium?

A
  • cosolvency
  • pH control
  • solubilisation
  • complexation
  • chemical modification
  • particle size control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe cosolvency.

A
  • cosolvency is used for drugs that are weak electrolytes or that are non-polar, to increase their apparent solubility in water.
  • cosolvents selected must be miscible in water and something that the drug can dissolve in as well.
  • solubility of drug is affected by the dielectric constant of the solvent system, therefore the blends should be between 25 and 80.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe pH control.

A
  • used for weakly basic and acidic drugs, whose extent of ionisation will ultimately affect its solubility.
  • pH control must be in line with product requirements as well.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe solubilisation

A
  • surfactants can be added to increase the solubility of a drug in a particular solvent system.
  • the concentration of these surfactants must be above their critical micellar concentration (CMC) –>micellar solubilisation.
  • large excess of surfactant is undesirable.
  • hydrophilic surfactants with HLB values above 15 are useful solubilising agents.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are some factors that affect the choice of solubilising agents?

A
  • toxicity and irritancy
  • miscibility with solvent system
  • compatibility with other components
  • odour and taste
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

It doesn’t matter how much surfactant is added because the excess surfactants are harmless. (T/F)?

A

false, excess surfactants can have harmful effects.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe complexation.

A
  • interaction of a poorly soluble drug with a soluble material to form a soluble complex.
  • process is easily reversible, as the complex is likely to be a macromolecule that is inactive.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe chemical modification.

A
  • involves the synthesis of soluble salts of the drug

- soluble salt may not have any activity and is converted back to the active base in the biological system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe particle size reduction.

A
  • use of technologies like milling to reduce the particle size of drug molecules and improve their solubility in water.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does one determine the minimum concentration of surfactant for the solubilisation of the drug?

A
  • use a series of vials, each with a constant concentration and proportion of solvent and surfactant.
  • add different concentrations of drugs into the vials.
  • calculate their optical density, and plot a graph of optical density against drug concentration.
  • the last drug concentration where the solution remains clear is the maximum drug concentration.
  • using the same procedure, calculate the MDC values of different concentrations of the surfactant (expand scope).
  • plot graph of MDC against concentration of surfactant.
  • point at which the drug starts to solubilise is the CMC.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly