special dosage forms Flashcards
How are micelles formed?
surfactants
sufactants
amphiphilic molecules described as having:
1) hydrophilic head
2) hydrophobic tail
How do surfactants arrange in water?
to minimise contact between hydrophobic tail + solvent
How are surfactants arranged in low concentrations?
align on surface of water
How are surfactants arranged in high concentrations?
self-assemble to form micelles
critical micellar concentration
concentration of surfactants above which micelles form
What does osmotic pressure depend on?
concentration of solute in solution
How can clinical micellar concentration be measured?
1) osmotic pressure
2) solubility of water insoluble molecules
3) light diffraction
4) surface tension
5) molar conductivity
molar conductivity
conductivity of electrolyte solution divided by molar concentration of electrolyte
What are phenolic compounds used for?
disinfection
What happens when you add
surfactants to water below the CMC?
surfactants locate at liquid/air interface reducing surface tension of liquid
What are liposomes formed from?
phospholipids
How do liposomes assemble in water?
to form lipid bilayer
Where do liposomes solubilise hydrophobic drugs?
bilayer
Where do liposomes solubilise hydrophilic drugs?
water core
What are liposomes used for?
1) protect drugs from degradation in vivo + prolong activity
2) reducing dose + side effect by drug targeting
3) favour absorption of drug through cellular membranes
4) oral/parental/transdermal/topical delivery of drugs
What are the 4 types of liposomes?
1) conventional
2) stealth
3) targeted
4) cationic
What are cyclodextrins used for?
1) increase aqueous solubility of drugs
2) increase chemical stability of drugs
3) enhance drug delivery to + through biological membranes
4) increase physical stability of drugs
5) convert liquid drugs to microcrystalline powders
6) prevent drug-drug/drug-excipient interactions
7) reduce local irritation after topical/oral administration
