special dosage forms Flashcards
what are micelles formed by?
surfactants
what are surfactants?
-amphiphillic molecules that have a hydrophilic head and a hydrophobic tail
what do micelles do in water?
-they arrange in order to minimise the contact between the hydrophobic tail and the solvent
-at low concs they align on the surface of water
-at higher concs they self-assemble to form micelles
-hydrophobic drugs are entrapped in the core of the micelles
what are liposomes formed by?
-phospholipids
what is the structure of phospholipids?
-as surfactants they are amphiphilic and have a hydrophilic head and two hydrophobic tails
what do liposomes do in water?
-they self assemble to form a lipid bilayer
-they can solubilise hydrophobic drugs in the bilayer
-they can solubilise hydrophilic drugs in the water core
what do liposomes do?
-they are used to encapsulate drugs that are toxic or labile
what does osmotic pressure depend on?
-the concentration of solute in solution
-as micelle form at the addition of each molecule of surfactant there is no increase of number of entities in solution
what are cyclodextrins used for in special dosage forms?
to enhance the solubility, stability and bioavailability of drugs
what is molar conductivity?
-the conductivity of an electrolyte solution divided by the molar concentration of electrolyte
what does conductivity depend on?
-the movement of charged particles in solution, the bigger the particles the slower their movement and the lower their conductivity
what is the relationship between micelles and surface tension?
-positioning of surfactants on liquid surfaces breaks solvent-solvent bonds reducing surface tension
-once micelles are formed no more surfactant place themselves on the liquid surface
go over this lecture with iPad for revision esp of graphs
