PH2107 - Solutions 3

Question 1

What can be used to enhance solubility using excipients that create disperse systems?

Answer 1

• surfactants
• emulsions
• vesicles / nanoparticles
• chelators / complexants

Question 2

What is a surfactant?

Answer 2

An amphiphilic organic compound comprised of hydrophobic groups (tails) and hydrophilic groups (heads)

Question 3

Give some examples of surfactants

Answer 3

• octanol (long chain alcohol, non-ionic)
• sodium dodecyl sulphate (anionic)
• benzalkonium chloride (cationic)
• cocamidopropyl betaine (zwitterionic)

Question 4

Give examples of amphiphilic biological compounds?

Answer 4

• phospholipids
• cholesterol
• glycolipids
• fatty acids
• saponins

Question 5

What is solubilisation?

Answer 5

Solubility can be improved by addition of a surface active agent (micellar solubilisation)

Question 6

What properties must a surfactant have used for solubilisation?

Answer 6

• non-toxic
• non-irritant
• miscible with the solvent system
• compatible with the other ingredients

Question 7

What effect do surfactants have?

Answer 7

Surfactants lower the surface tension of a liquid, the interfacial tension between two liquids or that between a liquid and a solid

Question 8

What do surfactants act as?

Answer 8

• detergents
• wetting agents
• emulsifiers
• foaming agents
• dispersants

Question 9

How do surfactant molecules migrate?

Answer 9

Surfactant molecules will migrate to the water surface, where the insoluble hydrophobic group may extend out of the bulk water phase, either into the air or, if water is mixed with an oil, into the oil phase, while the water soluble head group remains in the water phase

Question 10

What is an emulsion?

Answer 10

A dispersed system comprised of two or more immiscible liquids

• oily
• aqueous

Question 11

What are the two phases that make up an emulsion?

Answer 11

Disperse phase

Continuous phase

Question 12

What state are emulsions in?

Answer 12

Emulsions may be semi solids or liquids

Question 13

What determines the state of an emulsion?

Answer 13

The oil and water proportions

Route of administration

Question 14

How is an emulsion formed?

Answer 14

High energy input needed as they are thermodynamically incompatible

Question 15

What can be added to an emulsion to increase kinetic stability?

Answer 15

An emulsifier (emulgent)

Question 16

What is propofol?

Answer 16

A short-acting medication that results in a decreased level of consciousness and lack of memory for events. Its uses include the starting and maintenance of general anaesthesia, sedation for mechanically ventilated adults and procedural sedationWhat are microemulsions typically used for?

Question 17

What are microemulsions typically used for?

Answer 17

To kill microbes (bacteria, viruses), blood and sperm

Question 18

How much force is needed to make a microemulsion?

Answer 18

The smaller the droplet, the greater the surface tension and thus the greater the force to merge with other lipids

Question 19

How is a microemulsion made?

Answer 19

The oil is emulsified with a high shear mixer with detergents to stabilise the emulsion, so when they encounter lipids in the membrane or envelope of bacteria/viruses, they force the lipids to merge with themselves, disintegrating pathogen membrane

Question 20

What is a vesicle?

Answer 20

A supramolecular assembly of lipid molecules in an aqueous environment

Question 21

What is a bilayer?

Answer 21

A fundamental structural feature of a biological membrane

Question 22

What is a micelle?

Answer 22

A spherical aggregate, ~150nm of surfactant molecules dispersed in a liquid colloid

Question 23

What is a normal phase micelle?

Answer 23

A micelle with the headgroups facing away from the centre (oil-in-water micelle)

Question 24

What is an inverse micelle?

Answer 24

A micelle with the headgroups at the centre with the tails extending out (water-in-oil micelle)

Question 25

How are micelles useful in pharmacology?

Answer 25

Insoluble species can be incorporated into the micelle core, which is itself solubilised in the bulk solvent by virtue of the head groups’ favourable interactions with solvent species