Pharmacology Flashcards
main routes for drug administration in the skin
- topical
- transdermal
- subcutaneous
- other epithelial routes e.g. airways, conjunctival sac, nasal mucosa and vagina
model of the stratum corneum
Brick and Mortar model
drug delivery diffusion routes
intercellular
transcellular
transappendageal
vehicles
lotions (most water content) creams ointments gels pastes powders foams
describe lotion formula
suspension/solution of medication in water (if containing alcohol it can sting)
when are lotions used?
hair-bearing areas
creams formulation
semisolid emulsion of oil in water, containing emulsifier and preservative
are creams cosmetically acceptable
yes, non-greasy
describe ointments
semisolid grease, less cosmetically acceptable
gels formulation
thickened aqueous solutions containing high molecular weight polymers e.g. methylcellulose
pastes formulation
semisolids finely powdered material (ZNO). stiff, greasy and often used in bandages
describe foams
colloid with two or three phases
types of topical therapies
- emollients
- topical steroids
- anti-infective
- antipruritic
- keratolytic
describe emollients
used in dry/scaly conditions
300-500g per week
applied after bathing in direction of hair growth
describe topical steroids
vasoconstriction and anti-inflammation
range from mild to very potent
whole body application is 20-30g
Adverse of topical steroids
thinning of skin purpura rosacea telangiectasia systemic absorption (Cushing's) tachyphylaxis
types of anti-infectives
antiseptics (iodine, hydrogen peroxidetriclosan and chlorhexidine)
antiviral
antifungals e.g. nystatin, clotrimazole or ketoconazole.
examples of antipruritics
methanol
capsaicin
phenol
crotamiton
function of keratolytics
soften keratin
role of calcineurin inhibitors
suppress lymphocyte activation
factors that increase partitioning into the skin
- hydration of the skin by occlusion
- inclusion of excipients (increases solubility of hydrophobic drugs)
factors that affect absorption into the skin
nature of skin (site, hydration, thickness) drug preparation (concentration, salt, vehicle)
describe the subcutaneous route
needle into adipose tissue
how does the drug enter the systemic circulation by subcutaneous route
via capillaries or lymphatic vessels
disadvantage of subcutaneous route
slow absorption (can be a good thing) limited volume injected
why is the skin a good route for drug administration
- simple and non-sterile
- steady state plasma concentration
- avoids first pass metabolism
- drug absorption can be terminated rapidly
disadvantages of skin as a route of administration
only limited numbers can diffuse across the epidermis
describe transdermal drug delivery
adhesive patch
role of enhancers in an adhesive patch
interact with lipid matrix to increase permeability
