Itch Drugs Flashcards
what 3 main allergic skin diseases dominate in vet med?
- canine atopic dermatitis
- feline hypersensitivity (allergies)
- equine inset bite hypersensitivity
2 basic components: pruritis and skin inflammation = drugs need to be able to resolve both
-FDA requirement; at least 50% improvement
describe the neuroanatomy of itch/pruritis
itch sensation is transmitted from the skin (free nerve endings of peripheral sensory neurons) to the brain through unmyelinated C fibers (dorsal root ganglia) which detect itch-producing stimuli and relay signals via the spinal cord to the brain for processing
-the dominant symptom of human and canine atopic dermatitis is itch: abnormal sprouting of nerve fiber endings in the epidermis
describe the mediators/pruritogens of pruritis
- histaminergic itch: not as big a role in vet med
- non-histaminergic itch
describe IL-31’s role in itch
shown to induce delayed itch in humans and dogs
meaning it could be a possible drug target!
why do we use glucocorticoids for itch?
- they have rapid onset and are highly potent anti-inflammatory and anti-itch drugs!!
- the broadest targeting so will def stop the itch but also have many side effects
-can be used for multiple diseases (atopic dermatitis, flea bite hypersensitivity)
-generally do not divide dose into twice daily
-injectable (depo) is much more concentrated and doses are not really known so avoid!! - duration dependent on severity:
-very severely inflamed and suer itchy needs longer: like 2-4 weeks once daily admin and then taper
-generally give 30 days total (dose + taper) of steroids, just may have to extend if very severe - scabies:
-once kill mites, allergens will be released so give steroids plus anti-mite meds!! - recall the side effects of glucocorticoids
describe the patterns commonly seen in feline hypersensitivity dermatitis and what drugs are most commonly used
- symmetrical abdominal alopecia
- miliary dermatitis
- head and neck pruritis
- eosinophilic granuloma complex: indolent ulcer, eosinophilic plaque, eosinophilic granuloma
drugs:
1. oral prednisolone or dexamethasone
-issues with pilling so would prefer liquid but there is NO STEROID liquid approved for cats in the US
2. injectable: depo (avoid), dosage, frequency, and success unknown
3. oral dexamethasone sodium phosphate (is an injectable but can use off-label liquid oral if owner cannot pill cat)
duration: dependent on severity like in dogs
describe insect bite hypersensitivity and glucocorticoids
- also called cullicoides hypersensitivity, queensland itch, or sweet itch, or summer sores
-over 1000 cullicoides spp worldwide, multiple species can feed on the same horse
-hypersensitivity to proteins in cullicoides saliva
-bugs most active at dusk and dawn - we give glucocorticoids for this but side effects in horses include:
-hepatopathy
-muscle wasting
-altered bone metabolism
-hyperglycemia
-PU/PD
-increased susceptibility to infection
-possible predisposition to laminitis especially if underlying immunosuppressive condition
describe oclacitinib/apoquel
- a dose dependent JAK1/JAK2 inhibitor
- inhibits signaling of JAK1 cytokines
-IL-2, IL-4!!, IL-6, IL-13!!, IL-31!!! - rapid onset relief for canine atopic dermatitis and flea allergy hypersensitivity
- side effects are relatively rare
-urinary tract abnormalities, cutaneous masses, generalized demodicosis/serious infections
-but not recommended for patients with pre-existing neoplasia, potential risk for malignancy (so do what you can to keep the dose low!)
describe ilunocitinib/Zenrelia
- JAK1, JAK2, and TYK2 cytokines
-broader immunosuppression than oclacitinib - remember to discontinue prior to and beyond vaccination!!
- possibility for dose dependent anemia, TCP, leukopenia neutropenia, lymphopenia, eosinopenia, and monocytopenia
-and increased liver enzymes
-so routine bloodwork and liver panels!
describe oclacitinib in cats
- used OFF LABEL for feline hypersensitivity dermatitis
- dose dependent efficacy
-shorter oral half life so may need twice daily dosing - no clinical side effects but limited info on safety in allergic cats
-so rarely used long term in cats!! (2 months is longest really)
describe oclacitinib in horses
- no PK data available yet
- but have found that allergic horses have extremely upregulated IL-13 genes
-so oclacitinib seems most reasonable to give to help since targets that pathway
-early studies: horses have improved on this drug - no side effects found so far, but recommend CBC/biochem every few month if longterm use because so little data available
describe cyclosporin
- labeled for atopic dermatitis (calcineurin inhibitor)
-but take 4-12 weeks to max effect, so do NOT give alone to a severely allergic dog
-give apoquel or steroids for first bit to get through lag phase - many formulations
-compounded has low bioavailability, so avoid!
-anecdotally: Teva liquid seems to work best - recall cyclosporine side effects and how to overcome
- in cats: higher dosage than in dogs for feline hypersensitivity dermatitis
-cats also have a lag phase to effect so also add a secondary therapy for relief!
-give daily until marked improvement, and then taper (DO NOT TAPER if not improved)
-also recall cyclosporine + T. gondii in cats
describe lokivetmab/cytopoint
- monoclonal antibodies/biologics
-have monovalent affinity so bind to the same epitope
-caninized antibody that binds IL-31 cytokine - mostly canine (92%) but some mice (8%)
-dogs could develop autoantibodies to the mice part so with longterm use could reduce efficacy as dogs are able to breakdown the mice part - much more specific targeting than oclacitinib
-very effective in reducing itch, but not as effective at reducing skin inflammation
-so the more severe the presentation, the lower the chance of this drug working as a sole therapy - give as injectable therapy
-rapid onset (2-3 days)
-repeat monthly as needed
-unique safety: no immune suppression, no contraindications for other drugs, and use is not limited to any age
-side effects: potential inability to control skin inflammation
- in cats and horses:
-not used (caninized antibody = foreign protein)
