Ectoparasitic Drugs Flashcards
Ideal ectoparasiticide
Effective repellent and adulticide
Persistent in blood/ skin for 1-3m
Stable in sunlight and water/ shampoo
How are ectoparasiticides delievered
Transdermal
Lipophilic with large molecular wt.
Slow dermal absorption, low bioavailibility, large distribution, long t 1/2
Advantages of ectoparasiticide
Ease of application
Avoid challenges of first pass metabolism and GI degradation
Disadvantages of ectoparasiticide
Overdosing by clients (toxicosis)
Licking → oral absorption and systemic exposure
Pour-on food in animals require longer withdrawal pd and long t1/2
Macrocyclic lactones
Endoectocides (combo of ectocide and endocide): Avermectin(iver, aprino and selamectin) and Mibemycin (Moxidctin)
Spinosad
Macrocyclic lactones MOA
Toxic against insects, acarines and nematodes
Agonist of ligand-gated Cl channels (glutamade-Cl channel) → flaccid paralysis and inhibits larval development
T/F: Macrocyclic lactones have efficacy against cestodes and trematodes
FALSE
Macrocyclic lactones in simple stomach animals
95% absorbed after oral admin
Selamectin greater bioavail. for cats than dogs
Macrocyclic lactones in ruminal absorbtion
Absorbs 1/4-1/3 dose due to activation in the rumen
Oral bioavail. poor in ruminants
Macrocyclic lactones in ruminants
Strong absorption to Gi particulate digesta
Fat reservoir
Extensive/ reversible plasma tissue exchange
Low metabolism rate
The long half-life in ruminants are due to …..
The slow disposition kinetics present
Selamectin uses
Topical monthly for dogs and cats with ear mites and adult fleas
Prevents flea eggs from hatching
__________ is the only spot on product approved for control of K9 ____________
Selamectin
Sarcoptic mange
Toxicity of Macrocyclic lactones
10x safety in most animals
Acute toxicity: depression, ataxia, tremors, salivation, mydriasis, coma and death
Macrocyclic lactones and collies
P-gp mutation in collies (4 base deletion MDR1/ABCB1 gene)
↑ conc in the brain, safe @ norm doses
Spinosad MOA
Mix of 2 macrocylic lactones
Ectoparasite only
Nicotinic AChR allosteric acitvator
What does spinosad do to parasites?
Involuntary muscle contraction and tremors → death
Spinosad uses
Fleas: kills adults (4hr), prevent egg production
Sheep: blowflies and lice
Control beetles, flies and northern fowl mite
Spinosad toxicity
Don’t mixed with ivermectin (causes ↑ risk of ivermectin toxicities)
Fipronil PK
Deposits in sebum, sebaceous glands (reservior) and hair follicles
Forms a layer on S. corneum
Fipronil MOA
Acts on CNS target parasites
Active metabolites: fipronil sulfate (potent inhibitor)
Fipronil uses
Adult fleas
All stages of brown dog, American dog, long star and deer tick (on animal)
Kills larvae and eggs
Reported activity of fipronil
Sarcoptes, otodectes, trombicula, cheyletiella, trichodectes
Fipronil safety/ toxicity
Slight skin/ eye irritation
Risk ↑ with oral ingestion
GABA receptor antagonist (hyperactvity, excitability and convulsions)
Imidacloprid and Nitenpyram MOA
Mimics effect of ACh by competitive inhibition @ post-syn. nicotinic AChR (CNS of insects)
Imidacloprid PK
Surface translocation aided by body movement
Efficacy depends on contact with ectoparasites
Topical
Imidacloprid uses
Taken up by flea body contact with drug (dogs and cats)
Kills adult and larva fleas (1h)
No repellant activity
Side effects/ toxicity of imidacloprid
Nicotinic effects and hepatic effects
Careful with products because they’ll combine (cats)
When shouldn’t imidacloprid be given?
Puppies <7w old or kittens <4m
Nitenpyram (Capstar)
Safe and water soluble
Readily absorbed (100%) in GI
Nitenpyram (capstar) uses
Oral adulticide for fleas in cats and dogs
Rapid onset, kills adult fleas resistant to fipronil
3rd generation pyrethroids
Permethrin
Photo stability and potency
Spots on high conc, dogs only, no cats
MOA of pyrethroids
Gating kinetics of insect Na ions channels in nerves
Channel left open, repetitive discharges or membrane depol
Pyrethroid uses
Repellent and knock-down effect
Ectoparasites of domestic animals
Formulated with insect growth regulators, synergists or repellents to ↑ efficacy
Pyrethroid toxicity in cats
Deficient hepatic glucoronidation
Grooming after application
Muscle tremors, hyperthermia, seizures
Pyrethroid toxicity tx in cats
Wash the coat at home then at clinic
Methocarbamol +/- benzodiazepines
IVF if severe acidosis
Amitraz (Formamidine) MOA
Inhibits monoamine oxidase in CNS
Amitraz uses
Dogs: gen. demodicosis (mitaban), tick collars
Cattle: ticks, mites, biting louse, suckling lice
Swine: mange mite and louse
____________ can cause death in horses and dogs if used @ high doses
Taktic (amitraz)
Safety/ toxicity of amitraz
Horse: fatal from colon impaction
Cats sensitive
Don’t use in chihuahuas, preg, nursing bitches, puppies <3m
Signs of amitraz toxicity
Activates alpha-2- adrenergic receptors
CNS depression, bradycardia, PU, hyperglycemia, sedation (24hr)
Tx of amitraz toxicity
Atipamezol (alpha-2 antagonist)
Juvenile hormone analogs (insect growth regulators)
Signal insect to remain in immature stage and not develop to adult
Methoprene, pyriproxifen, fenoxycarb, cyromazine
Insect development inhibitors (insect growth regulators)
Interferes with development of insect exoskeleton by inhibiting chitin synthesis or deposition pathway
Diflubenzuron or lufenuron
Isoxazoline drugs
Fluralaner**, afoxolaner, sarolaner
Isoxazoline MOA
Block GABA and glutamate-gated chloride channels
Isoxazoline uses
Kills fleas and ticks
Fluralaner 12 w efficacy
Afoxolaner 5 w efficacy
