Lec 6 Skin Penetration & Drug Delivery Flashcards
What is the difference between transdermal and topical drug delivery?
Transdermal -diffusion of drugs through various layers of skin into systemic circulation
Topical- targeting pathological sites within the skin
What is the advantage of topical drug delivery?
Avoid first pass metabolism
Easy drug control
Better patient adherence
What is the disadvantage of topical drug delivery?
Only drug molecules with specific physicochemical properties that do not harm the skin can be used
Intra/Inter patient variability
Metabolism in the skin
Skin is strong barrier to for drug delivery
What are the 3 permeation pathways
Transcellular- though the cells
Intercellular- between the cells
Transappendegeal- through the hair follicles and sweat ducts
What are the ideal drug properties for topical drug delivery?
Low molecular weight
Balanced partition co-efficient
Low melting point
Must not irritate the skin
What are the 3 factors which affect drug penetration?
Physicochemical factors
Biological factors
Formulation factors
List some physiochemical properties
J=flux
Particle size less than 200nm to deliver through hair follicles
List some biological factors
Age
Race
Sex
Condition of skin
What are liposomes?
Liposomes are vesicles that are made up of one or more lipid bilayers surrounding the internal aqueous compartment. The most commonly used lipid is phospholipid, which form the backbone of the bilayer.
What are the advantages of liposomes?
- Low toxicity profile
- Ability to incoporate both hydrophilic and hydrophobic drugs
- Protection of drug from inactivation in blood stream
- Variability in size to incorporate large/small drug molecules
What are the disadvantages of liposomes?
- Stability and low entrapment efficency limit their use as susceptibility of phospholipids to dehydration and oxidation
- Preparation is tedious
- Not very stable
