Antinematodals Flashcards
What are examples of Avermectins?
Ivermectin
Selamectin
Doramectin
Eprinomectin
What are examples of Milbemycins?
Milbemycin oxime
Moxidectin
What gives rise to the collective name for Macrolides?
The macrocyclic ring
What is the mechanism of action of Avermectins and Milbemycins inside the insect or parasite?
Through the stimulation of a receptor site for glutamate
What does stimulation of the glutamate receptor cause?
Muscle paralysis that causes starvation or move away from their infection site and die
What parasites are macrolides are ineffective against because they do not have glutamate receptors?
Tapeworms and flukes
Do Macrolides produce a well-documented toxicity?
Yes
Because macrolides are lipophilic, they can readily diffuse through and potentially gain access to the GABA receptors causing toxicity. Why does toxicity not occur every time a macrolide is administered?
Because of a special protein pump P-glycoprotein (P-gp) that moves drugs from the brain side back into the blood
Where else are P-glycoprotein pumps located?
Liver and GI tract
What affects the P-gp pump and allows macrolides to accumulate within the brain, increasing the risk for toxicity?
Inhibited by other drugs
P-gp can be defective
What drugs can inhibit the P-gp?
Calcium channel blocker antiarrhythmics
Cyclosporine immunosuppressant
Antifungal agents Ketoconazole or itraconazole
What breeds of dog have a genetic defect in the gene that codes for their P-gp?
Collies and other related breeds
What is the gene that codes for P-gp known as?
Multiple drug resistance 1 genes (MDR1)
ATP-binding cassette-type B1 genes (ABCB1)
What are the clinical signs of animals with a defective P-gp pump?
CNS depression Hypersalivation Vomit Become ataxic Stagger Progress to depression Unresponsiveness Bradycardia Mydriasis Loss of menace response Coma
Is there an antidote for avermectin or milbemycin toxicosis?
No. Recovery requires the animal be kept alive in a comatose or severely depressed state for days to weeks before the effects of the drug wear off
What explains how avermectins and milbemycins readily penetrate many tissues and persist at low, but still effective concentrations for a long period of time?
Lipophilic nature of macrolides
What else are macrolides effective against when administered by oral or injection because they can penetrate into the tissues and the tissue fluid?
Mites
Sucking lice
Feeding ticks
What can macrolides contaminate for an extended period of time?
Milk
What are macrolides excreted by?
Liver into the feces
What explains the long-lasting effect of macrolides in the body?
The enterohepatic circulation in conjunction with the persistence in the tissues
What is the first macrolide to be available for use in vet med?
Ivermectin
What does Ivermectin treat?
Heartworms
Intestinal & external parasites
Ivermectin is combined with what to produce parasiticides with a wider spectrum of activity?
Other anthelmintics
Heartgard Plus is combined with what and what does it treat?
Ivermectin & Pyrantel pamoate
Control intestinal ascarids
Iverhart Max is combined with what and is used to treat what?
Ivermectin + Pyrantel pamoate + Praziquantel
Tapeworms, intestinal ascarids
Small animal toxicity is associated with waht?
Accidental exposure to large animal products and not with small animal products
What does Ivermectin require to be effective against parasites?
Small concentrations
What is the normal dose of Ivermectin to prevent heartworm?
0.006 mg/kg
What dose of Ivermectin is toxic to Collies?
0.1 mg/kg
What medication is on the shelves as Revolution and is a broad-spectrum endectocide?
Selamectin
What is Selamectin primarily used as?
Heartworm preventative
Also effective against GI parasites & external parasites?
What external parasites is Selamectin effective against?
Fleas
Ear mites
Sarcoptic manage
One tick species
Selamectin is approved as what kind of medication?
Monthly topical application in dogs and cats
How much of the topically applied drug do dogs absorb systemically?
4%
How much of the topically applied drug do cats absorb systemically?
74%
Because of the high absorption rate what else is topically applied selamectin approved to treat in cats?
Ancylostoma tubaeforme and Toxocara cati
Why is toxicity in breeds with MDR1 gene mutation rare?
Because of the route of administration and the relatively low amount of drug absorbed in dogs
Is topical application still effective as a heartworm preventative even after the pet is bathed?
Yes
What does oral contact with the compound produce?
Hypersalivation and vomiting
Does topical application overdoses of 10x the prescribed produce significant signs in dogs and cats?
No other than hypersalivation
What macrolides are approved for use in cattle?
Doramectin and Eprinomectin
What macrolide is on the market as Dectomax, is available as an injectable and topical “Pour-on” and approved for use in cattle and swine?
Doramectin
What macrolide is on the market as Eprinex, approved for use as a topical application in cattle, subcutaneous injection in beef cattle and is effective against internal parasites, grubs and mange?
Eprinomectin
How many days does the subcutaneous Eprinomectin injection in beef cattle (LongRange) provide antiparasitic activity?
100 to 150 days
What antinematodal was originally used against agricultural insects?
Milbemycin Oxime
Milbemycin Oxime orally administered tablets are FDA approved to treat what?
heartworm prevention in dogs & cats
Treatment/control for hookworms & roundworms in dogs and cats
Whipworms in dogs
Topically applied treatment of ear mites in cats
What products contain Milbemycin Oxime?
Interceptor
Sentinel
Trifexis
What does Milbemycin Oxime show some promise in treating?
Demodectic mange
Milbemycin Oxime is nontoxic to what breed when doses 20x the regular dose?
Collies
What products contain Moxidectin?
Cydectin
Quest
Advantage Multi
ProHeart 6
Does ProHeart 6 clear the adult heartworms or the circulating microfilariae?
No. It is just used as a heartworm preventative
Does ProHeart 6 prevent hookworm reinfection?
No it just kills the adults and migrating larvae
Moxidectin is used in cattle and horses as what drug forms?
Pour on for cattle
Oral gels in horses
What does Moxidectin products prevent in cattle and horses?
Intestinal parasites Mites Cattle grubs Horse Stomach bots Lice Flies Nematodes
What product comes as a combination of Moxidectin and Imidacloprid?
Advantage multi
What is Advantage multi used for?
Approved for heartworm prevention
Treatment & control of roundworms, hookworms, whipworms
Treatment of sarcoptic mange & fleas
Advantage Multi is the only FDA approved product for what?
eliminating the circulating microfilariae in dogs
What is the mechanism of action of Benzimidazoles?
Attack Beta-tubulin proteins
What are Beta-tubulin proteins involved in?
Cell division Maintaining cell shape Cell motility Cell secretion Intracellular transport
What does attacking the Beta-tubulin proteins accomplish?
Disrupts the normal cellular function & eventually kill the parasite
How long does it take for benzimidazoles to work?
Up to 24 hours
Multiple exposures to the drug over 3 or more days
What have been noted at very high doses of selected benzimidazoles?
Teratogenic effects
Benzimidazoles are recognized by what?
Azole suffix
What are examples of benzimidazoles?
Thiabendazole Fenbendazole (Panacur, Safe-Guard) Oxibendazole (Anthelcide EQ) Albendazole (Valbazen) Fabantel (Drontel Plus)
What is considered the prototype drug for the benzimidazoles?
Thiabendazole
Which benzimidazole has a wide range of activity against ascarids & strongyles, and some antiinflammatory and antifungal activity?
Thiabendazole
Thiabendazole has been used for a long time, and because of this what has been documented with this drug?
Parasitic resistance
What has a wide spectrum of activity against nematodes, effective against a limited number of tapeworms and is used as an oral paste/solution in horses, granules in small animals and exotics?
Fenbendazole
What has been used for a long as an equine dewormer to control large and small strongyles, large roundworms, pinworms, and threadworms?
Oxibendazole
What is used to treat intestinal nematodes, lungworms, trematodes, cestodes and protozoa in livestock?
Albendazole
What has been linked to teratogenic effects and bone marrow suppression?
Albendazole
Which benzimidazole is a “Prodrug”?
Febantel
What is a “prodrug”?
It must be converted by the metabolism to the active form of the drug
In the case of Febantel this means fenbendazole & oxibendazole
Febantel is not available as a stand alone antiparasitic. What is it combined with and what is the name of the drug it is used in?
Combined with pyrantel and praziquantel to form Drontal Plus