Lecture 17 3/27/24 Flashcards
What are the potential uses for topical therapy?
-focal lesions
-adjunct to systemic therapy
-decrease bacterial resistance
-treat ectoparasites
-management of chronic/recurrent skin diseases
What are the advantages of topical therapy?
-reduction in systemic drug absorption and adverse reactions
-decreased risk of antibiotic resistance
-useful in bacterial resistant pyoderma
-adjunctive and synergistic effects in overall management of skin disease
-often less expensive and may not require a prescription
-empowers owner to participate in treatment
What are the disadvantages of topical therapy?
-more time consuming and labor intensive
-messier, with potential odors or residues
-localized adverse reactions
-client education and compliance can be harder to achieve
What are the limitations of topical therapy?
-long coat breeds: often need to trim for treatment to be effective
-cats: self-grooming limits which products can be used and if they will be efficacious
-owners: topicals are only as effective as the owner
What are the three mechanisms of transepidermal delivery?
-intracellular; penetrates keratinocyte
-intercellular; pass through or dissolve in lipid bilayer matrix
-transappendageal; enters follicles and/or glands
How does thickness of the stratum corneum impact absorption?
increased thickness of the stratum corneum will decrease absorption
How does absorption differ between acute and chronic lesions?
-acute lesions and inflammation increase absorption
-chronic lesions decrease absorption
How does total surface area impact absorption?
having a product on more skin provides potential increased absorption and greater systemic effect
What determines diffusion across the barrier?
-active ingredient
-vehicle
What is the role of the vehicle?
-facilitate application and absorption
-CANNOT force penetration if active ingredient is incapable of penetrating on its own
What must be considered when selecting a vehicle?
-ability of vehicle to hydrate stratum corneum
-occlusive vehicles increase absorption
-stability of the drug in the vehicle
-interactions between vehicle, active ingredient, and stratum corneum
Which factors impact the ability of an active ingredient to diffuse across the barrier?
-concentration and solubility
-rate of release from vehicle
-diffusion coefficient
-size of molecule
-pH
-temperature and hydration
What are the characteristics of acute lesions and product choice?
-erythematous, erosive, often exudative
-do not use occlusive vehicle; would seal infection
-do not use alcohol-containing products
-good for lotions
How do subacute lesions appear?
-erythematous
-inflamed
-not exudative
What are the characteristics of chronic lesions and product choice?
-thickened with excess stratum corneum
-do not use lotions; too drying
How should the patient be prepped prior to topical treatment?
clipped and cleaned
What are the characteristics of water based vehicles?
-include shampoo, sprays, and mousses
-contact time of 10 min.
-can be adjunct or sole therapy
-hydrating at correct time
-dehydrating/macerating with prolonged contact
What are the characteristics of lotion vehicles?
-can be a solution (ingredient does not settle out) or suspension (requires shaking)
-can be drying
-not recommended for chronic lesions
What are the characteristics of emulsion vehicles?
-oil in water
-low owner compliance due to greasiness of dogs after treatment
What are the characteristics of gel/cream/ointment vehicles?
-occlusive
-used for chronic lesions
-not recommended for acute lesions
What are the characteristics of powder vehicles?
-messy
-possibly used for ectoparasites
-poor absorption of most drugs except glucocorticoids
What are the characteristics of propylene glycol on its own?
-anti-bacterial
-anti-fungal
What are the characteristics of propylene glycol as a vehicle?
-enhances absorption
-keratolytic
-hygroscopic
-most common cause of contact reactions
What are the characteristics of DMSO on its own?
-anti-ischemic
-anti-inflammatory
-analgesic
-anti-bacterial, fungal, viral
-decreases fibroplasia
