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Pharma midterm 2 ectoparasiticides > Ectoparasiticides > Flashcards

Ectoparasiticides Flashcards

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1
Q

What are contact poisons?

A

on the surface of animal, when the parasite lands on body they will be killed

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2
Q

What are systemic agents?

A

drug is inside the animal, when a parasite comes, to suck blood or lymph, they take the drug with them

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3
Q

Insect growth regulators (IGRs):

A

acts against the insects, where there are metamorphosis fleas, flies

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4
Q

Repellents (DEET, pyrethroids):

A

keeps the parasites away from the animal, important against the flies and mosquitos, phlebotome sand flies, ticks

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5
Q

Selective toxicity of the drugs in regards to the pharmacokinetics

A
  • Slow metabolism
  • Blood-brain barrier (eg. P-glycoprotein-pump ivermectin) pumps out the drugs, makes the drugs not so toxic
  • slow absorption, large molecules, very good because in the system of the body the concentration isn’t high enough to cause clinical signs
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6
Q

selective toxicity in regards to pharmacodynamics

A
  • acts on different receptors and channels
  • eg. GluCl channels (only in insects and parasites)  depolarization or hyperpolarization
    o agonizing: open, chloride ions goes inside the cell hyperpolarization  paralysis of the parasite
    Ivermectin (macrolide)
    o antagonist: chloride channels does not open  depolarization excitation
    fibronyl??
  • nACh receptor sensitivity: imidacorporate (Advocate, advantex) antiflea agent, acts against fleas, very
    high selectivity and affinity to the flea nACh receptor compared to mammals or birds
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7
Q

the most common route of administration of ectoparasiticides?

A

Dermal absorption

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8
Q

How is the absorption of ectoparaciticeds?

A

slow but good
they are large, lipophilic molecules
low Cp - not so toxic

prolonged absorption from the site of administration (subcutaneous tissue, sebaceous glands) – continuous and prolonged effect

Poor-moderate amount crosses the blood-brain barrier, if they penetrate the p-glucoprotein pump will protect the nervous system

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9
Q

duration of action in different applications

A
  • collars 4-8 months – impregnanted, slow release
  • spot on 4-12 weeks – not a modified release, put on the skin, addtives helping with prolonged duration
  • spray, bathing days
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10
Q

Organophosphates

chemical characteristics

A

S least toxic (O -> F)
high lipophilicity
sensitive to alkaline pH
becomes more toxic with longer storage

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11
Q

organophospahtes absorption

A

good, lipophilic

less toxic when used dermally

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12
Q

distribution of organophosphates

A

excellent

spcial barriers BBB

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13
Q

metabolism of organophosphates

A

Partial activation – in the liver

Diazinon (t1/2hours)  diazoxon (t1/2 days)

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14
Q

Excretion - organophosphates

A

80% urine metabolites

20% faeces

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15
Q

mechanism of aciton - organophosphates

A

contact poison

irreversibly inhibits acetylcholin esterase

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16
Q

side effects of organophosphate (in connection with receptors)

A

Muscarinic acetylcholine receptor symptoms

  • Bradycardia
  • Bronchoconstriction
  • Myosis
  • GI: emesis, diarrhea
  • Salivation
  • Lacrimation
  • Urination

Nicotinic acetylcholine receptor symptom

  • Excitation
  • Muscle convulsion
  • tremor
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17
Q

antidotes organophosphates

A

SLUDGE - atropine

enzyme reactivation - pralidoxime, obidoxime

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18
Q

application and spectrum - organophosahates

A

broad spectrum in most species - diazinon
fleas, ticks, lice, mites, myiasis

dipping in sheep

varroosis of honeybeeds - coumaphos
- fume strip

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19
Q

carbamates - toxicity, MoA, agent, antidote, pharmacokinetics, spectrum, application

A

Similar to organophosphate, but less toxic

Inhibits acetylcholine esterase reversibly

Agent: propoxur (Bolfo®, Kiltix®)

tropine as antidote)

Pharmacokinetics: less lipophilic, oral vs dermal (LD50 higher than oral one)

Fleas, ticks

Collars (frequent), aerosol sprays, shampoos

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20
Q

generallly about pyrethroids

A

One of the most frequently used endectoparasiticides
Repellent effect, keeps the parasites away
Good against flies, ticks and mosquitos

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21
Q

generations of pyrethroids

A

Tetramethrin (NeoStomosan) : 1st gen.

Permethrin (ExSpot, Advantix, Vectra) :2nd gen.

Deltamethrin (Scalibor) :2nd gen.

Flumethrin (Kiltix, Foresto): 2nd gen.

1st generation: toxicity, residual activity, lower stability

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22
Q

Pyrethroids - mechanism of action

A

increases Na+ channels - constant depolarization
also known as knock down or hot foot effect

contact poison + repellent

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23
Q

resistance - pyrethroids

A

Ticks: still OK
- fipronil-tolerant brown dog tics resistant
Fleas: resistance is common
Poor efficacy against mange mites
Fly control
Moderate efficacy against Varroa mites (resistance!)

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24
Q

name of the products that takes care of varroosis

A

flumehtrin, fluvalinate

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25
application of pyrethroids
Foresto can be used in cats – low dose, collar – the release is slow and continuous spot on – total amount on the surface, large concentration, don’t give to cat
26
toxicity of pyrethroids
Safe in warm-blooded animals (↔ cat spot on) - Tremors, seizures, excitation Fish are especially sensitive – don’t let dogs go swimming when it has been applied Antidote Ø - Can only treat it clinically Intralipid 20% sequestration - Contains lipid - Closes pyrethroid molecules, letting them be excreted before they act in the nervous system Favourable prognosis in most cases (within 24 hours) + LOCAL IRRITATION, ALLERGIC REACTIONS - White toy breeds Similar to organophosphate - Convulsion - Tremor - Salvation Main difference is that the pupils are dilated – mydriasis
27
Amitraz (formamidine) - what neurotransmitter is it most selective to?
octopamine (doapmine, noradrenaline, inhibition of serotonine reuptake)
28
amitraz - mechanism of action
MAO-inhib. + α2 agonist
29
amitraz - kinetics
moderate absorption (p.o. 13% > dermal), half-life 23 hours in dogs
30
amitraz - spectrum
MANGE MITES, DEMODEX, ticks, 8-legged arthropods
31
amitraz - application
0,025% solution – safe concentration (dipping), collar, impregnated strips
32
amitraz - TI and safety
narrow - especially in eg, chihuahua, fe oral administration is more toxic storage: light, air
33
amitraz - side effects
alpha2 agonist: sedation, vomiting, bradycardia, hypothermia, emesis, hyperglycaemia (not in DM) Horses: alpha2-agonist, decreases the motility of the GI tract – leads to paralytic ileus
34
amitraz - antidote
atipamezole 0.05 mgkg
35
Macrolides - mechanism of action
GluCl channel agonist: channel opens and chloride goes in -> hyperpolarization -> paralyzis (only in nematodes and ectoparasites) not acting in mammals and birds GABA agonist: inhibitory receptor -> leads to paralysis in the animal, p-glucoprotein pump funciton penetrating the BBB, will pump it out before it acts, quite safe in the animal
36
macrolides - spectrum
Endectocides Fleas – only selamectin (stronghold) Mange mites – all are good (ear mites as well) Demodex spp (differences!) -> moxidectin (1 weekly – 4 times more frequent – more expensive for owner) and milbemycin (1x daily) Myiasis – fly larvae infestation Ticks (slow killing, not repellents) – not enough to prevent the diseases carried by the tick
37
how to test if a dog (breed) is suspecte to have MDR-1 gene missing
probe therapy
38
which breeds are predisposed to MDR-1 gene missing?
- Collies (not all are sensitive – individual genetic mutation) 70-75% - Australian sheepdog – 50% - Bobtail and german shepherd – 10% - Shelties and border collies – 5%
39
macolides - products and application
Orally - milbemax, nexgard spectra (milbemocyin) milprazon Spot on – stronghold (selamectin) Bravecto – amoxidectin Injection in large animals
40
Fipronil (frontline) - MoA - disadvantage? - applicaiton
GABA-antagonist  excitation Relatively slow effect (8h 40-60%) against parasite, a disadvantage Spot on, spray (frontline)
41
fipronil - pharmacokinetics
A: Good distribution in the skin (sweat and sebaceous glands)  good residual activity (bathing) can last for 1 month As a spray only a few days The animals should not bathe or swim for 48h after application (rainy days) D: Minimal systemic effect – safe for dogs and cats, no poisonous clinical signs Shedded hair > 2 weeks (Dermatophagoides farinae) - Allergy management Skin particles  into the environment
42
animals susceptible for fipronil?
rabbits
43
pyriprole
``` Derivate of fipronil Similar characteristics, GABA-antagonist  excitation in the parasite Fleas, ticks  decreased sensitivity - Resistance has not yet been observed Much more effective, but slow absorption (50%), Ø bathing within 48h Cats, rabbits Ø - Can lead to stronger systemic effects Dogs 3-10x overdose Prac-tic is used as a spot on ```
44
indoxacarb (activyl) - MoA - resistance - metbolism
Sodium channel blocker hyperpolarization  paralysis of parasite Also used in agriculture resistance, efficacy is not so high (decreased sensitivity?) Prodrug  bioactive metabolite (selective toxicity) cleavage of 2 methoxy group effective flea control (adult, larva, egg!)
45
indoxacarb - spectrum
Only against flea Feeding and oviposition stops within 0-4 hours Death within 4-48 hours (not very quick) Flea allergy dermatitis (FAD) – good agent against it
46
indoxacarb - application + safety
Spot on – not give to cat Safe usage – prodrug and is activated inside the parasite Environmentally safe
47
neonicotinoid insecticides - MoA
ACH agonist -> depolarization -> excitation
48
neonicotinoid - selective toxicity
560x affinity to nACh receptors of parasites acts fast environmental toxicity
49
neonicotinoid - generations
Only 1st and 3rd generation is used: imidacloprid (Advantage family, Foresto)1st gen. – spot on – very toxic for environment, cannot be used anymore, kills the bees dinotefuran (Vectra) 3rd gen. – pour on, lower dose needed, no resistance yet, more toxic for environment (honey bees) nitenpyram (Capstar) 1st gen. – tablet
50
DINETEFURAN+PERMETHRIN+ PYRIPROXYFEN (VECTRA 3D SPOT ON A.U.V)
``` Cats and dogs Fleas only Permethrin against tics (not in the ones for cat as it is dangerous in spot on) Pyriproxyfen: Larvae, puba, and eggs Doesn’t kill the adult flea ```
51
imidacloprid - drug names - effective agaisnt? - environemntal issues? - safety? - application
Advantage, Advantix, advocate, forest A.U.V One of the most effective agents against fleas, rapid action (within 6 hours >95%) – flea dermatitis too Fleas, for 4 weeks Epithelial debris! – when it goes to the environment it can kill the dust host mite – allergy condition 5-20x overdose is still safe (tremors, seizures?) Collar(delayed duration of action, several months), spot on + permethrin (Advantix) – dont put in cat + flumethrin (Foresto) – impregnated collar, releases drug slowly – can be put on a cat + moxidectin (Advocate) – macrolides (amoxidectin) Take care of the empty boxes – honey bees
52
isoxazolines - drug names - MoA - safety - negative effects?
Oral antiparasitic drugs originally also as spot on now Fluralaner (Bravecto®) Afoxolaner (Nexgard®) Sarolaner (Simparica®) Lotilaner (Credelio®) – GABA-antagonist, glutamate-gated Cl-channel antagonist Overdose: excitation, tremor (unfrequent with overdoses, very expensive) Plan for using it in humans against malaria and other mosquito born disease Drawbacks of spot on’s/collars – contact dermatitis – bathing/washing off/getting wet – usually does not cover the whole body – small dogs are very sensitive – contact dermatitis
53
efficacy of isoxazolines
Fleas + ticks Fleas within 8 hours will be killed Ticks within 12 hours (Lyme, Babesia) No repellent effect, enough to prevent to get the lyme and babesia from the tics – it needs one day or 1 and half day to inject the disease Mange mites – very good, due to the prolonged effect Demodex spp. – really good, first choice Poultry: Dermanyssus gallinae (fluralaner) Used in large animals too – not sheep or cattle Mainly small animals
54
combinations of isoxazolines used in small animal medicine
Sarolaner + selamectin – stronghold plus | Afoxolaner + milbemycin – nexgard spectra
55
pharmacokinetics of isoxazolines
Oral absorption: tmax 1 day Feeding (2,1-2,5x) fluralaner ↔ sarolaner, afoxolaner High plasma protein binding – binding to albumin Slow metabolism Enterohepatic circulation – when it is excreted into the bile from the GI will be reabsorbed (fluralaner + longer duration) Accumulation in adipose tissues – it will increase the duration of action, elimination from fatty tissue takes time – goes to the blood circulation after
56
half-life and side effects of isoxazolines
long half-life (10-15 days) -due to the slow metabolsim and high plasma binding side effect: vomiting, if the drug is not given with feed (fluralaner also increased absorption)
57
pharmacokinetic differences of isoxazolines
Afoxolaner: also excreted by kidneys (avoid with kidney patients) Fluralaner (0,01%), sarolaner: almost entirely via bile Enterohepatic circulation: fluralaner
58
toxicity of isoxazolines
Large differences between LD50 and therapeutic doses Sarolaner: 1x, 3x, 5x doses, 8 weeks old puppies - 3x overdose: tremors, ataxia (12 mg/kg) - 5x overdose: seizures, tremors, ataxia (20 mg/kg GABA-antagonism! – resolves within 24 hours Overdose: excitation
59
insect growth regulators
It will not kill the adults, it will influence the other stages of the life cycle: egg laying, stop the eggs from hatching, larvae cannot become pupa and pupa cannot become adult It will only act against insects that develop with metamorphosis so not against tics and mites
60
juvenile hormone analogues
Methoprene (Frontline Combo®) Pyriproxyfen (Duowin®, Vectra 3D®)  acts for even 48 days Ø adulticide effect! Inhibition of larval development (through eggs, pupas, and also with digested blood - Adult faceas and directly) Deformity of mature forms, if they survive – no wing development Light, residual activity: pyriproxyfen > methoprene
61
chitin synthesis inhibitors
(mainly in agriculture) lufenuron (Program®) – previously used (tabl) novaluron not used in veterinary practice

Pharma midterm 2 ectoparasiticides (1 decks)

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