What is Selamectin Toxicity ?
Selamectin is a medication that is both an insecticide and dewormer that is used for both dogs and cats. Although this drug is usually administered topically, it can also be administered by injection or by oral tablet, and it works by paralyzing the nervous system of the parasite. When the medication invades the system in large enough quantities, it can have an adverse effect on the central nervous system. Dogs in the herding breeds, like Collies, are more susceptible to selamectin toxicity than other breeds.
Selamectin, the active ingredient in the insecticide and dewormer Revolution, can have a toxic effect on the central nervous system if introduced in large enough quantities.
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Symptoms of Selamectin Toxicity in Dogs
The symptoms of selamectin toxicity or overdose are primarily related to its effects on the central nervous system.
- Exaggerated movements
- Excessive drooling
- Hair loss at application site
- Inability to rise
- Loss of coordination
- Muscle tremors
- Pupil dilation
- Rapid breathing
- Sensitivity to touch
- Sudden death
- Imidacloprid - The primary active ingredient in medications such as Advantage Multi, this dewormer paralyzes the parasites, eventually killing them; herding breeds may have a higher susceptibility to toxicity due to this drug
- Ivermectin- Used in the commonly used heartworm medication Heartgard, Ivermectin also uses paralyzation to kill the parasites infecting your dog; this drug can be more dangerous for herding breeds like collies than other dogs
- Lufenuron- This ingredient is used in conjunction with the other dewormers and prevents the parasite eggs from hatching
- Milbemycin oxime- Found in both Interceptor and Sentinel, this dewormer targets the nerves of the parasites to kill them
Causes of Selamectin Toxicity in Dogs
The medication Selamectin targets the GABA receptors in nerve cells, which blocks the signals of the neurons in the parasites, paralyzing and then killing them. The only GABA receptors in mammals are in the central nervous system, which is somewhat protected from the effects of the medication by the brain-blood barrier, but excessive concentrations of selamectin can cause toxicity. This can happen either because the dog receives substantial overdoses from the oral or injectable version of the medication, or due to the animal licking off the topical solutions.
Diagnosis of Selamectin Toxicity in Dogs
If your pet is showing indications that they have ingested any of the selamectin, which is usually administered topically, your veterinarian will likely order a biochemistry profile, complete blood count, and urinalysis as well performing as a full physical examination. If the ingestion of the medication was not witnessed, your veterinarian would take particular note of any opportunistic eating that was suspected or observed as there are other medications and plants that can cause similar symptoms.
In addition to environmental dangers, data regarding concurrent supplements or prescriptions that are being administered to your dog will be needed in order to reveal other toxins or drug interactions that may be at the root of the symptoms. Evaluation of the stomach contents and feces will often reveal residue from the medication, as will close examination of samples from the animal’s fat or liver. Supportive treatment will often start before a definitive diagnosis is made due to the severity of the symptoms.
Treatment of Selamectin Toxicity in Dogs
Preliminary treatments will be supportive, including IV fluids to prevent dehydration and combinations of electrolytes and sugars to adjust for any imbalances. Further therapies
will depend upon the original method of administration, the amount of the medication that made it into the dog’s system and if any symptoms have already become apparent. If the Selamectin was ingested and was consumed recently, then vomiting will be induced as soon as possible to prevent the absorption of the toxins into the bloodstream.
If the exposure was more than an hour or two before treatment, the attending veterinarian might choose to perform a gastric irrigation under general anesthetic to remove the neurotoxin from the patient’s digestive system. Activated charcoal will then be dispensed to the patient in an attempt to soak up as much of the toxin as possible. This step may be helpful not just when the dewormer is ingested, but also in cases of overdose by injection or topical exposure. Supportive measures will be continued until the symptoms are eliminated. Antiseizure remedies may also be utilized if tremors become uncontrollable.
Recovery of Selamectin Toxicity in Dogs
Plenty of fresh water should be made available for patients recovering from poisoning, and extra bathroom breaks will be needed as both the toxins and the medications make their way through the patient’s digestive system. Dogs that are recovering from anesthesia, as would be required for gastric irrigation, may have coordination difficulties and be confused and disoriented until the anesthesia has cleared their system. Isolation from other pets and from children is generally advised until the medication has a chance to fully clear from your companion’s system. In cases of poisoning, your veterinarian may recommend more frequent monitoring of your pet’s blood chemistry levels in the future, particularly in relation to kidney and liver functionality or impairment.
Selamectin Toxicity Questions and Advice from Veterinary Professionals
I have a 8 week old Chihuahua and the Vet gave it Revolution 3 days ago. This puppy cry all night long and finally got to feeling better. Last night it is showing blood in stools. Is this normal? I have never had a puppy treated with this medicine.
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What else can I do to help get my dog over topical toxicity
To selamectin. The dog is 10lbs 11 oz in weight.Has been
given 10-20lb dose .can't get his dirrhea stopped.We thought
He has been having food senceitivitys.We are now c onvinced it' the revolution.
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We gave our 5kg 10 yr old toy poodle Revolution Flea Treatment a stronger dose (5.1-10kg). Two days later he was confused when we threw the ball (which was a first). We made an appt with the vet asap and that morning our dog yelped in pain and intermittently over several days while we saw several vets that all said he looked very healthy. We were then told they questioned menegitis and he had the works (bloods, xray, ultrasound). The vet said the xray looked severe and that he needed very urgent neck surgery but when we saw the surgeon he said his neck (xray looked fine and normal). The surgeon think he may have a leaking disk in the neck although nothing is showing on xray. He suggested 1 month's crate rest and if he jumped once, we were to start again. We are on month 2. The surgeon suggested we could do an MRI or CTScan to determine the exact cause for $2000-$4000!!! It is all very coincidental and we are wondering if the selemectin caused a problem? Have you heard of anything like this? Our dog is now on Metacam, Gabepentin and Clomicalm to help calm him a bit and so difficult to say if the problem is improving.
Thanks so very much Dr. Turner. When I went into the vet's office, the vet nurse was very busy and grabbed the 5.1-10kg dose. I told her that Piggy usually got the package for the smaller dogs but she insisted that it was perfectly fine and that it could be given to kittens. I wish now I had spoken up although I had said to her he does get sensitive to the flea treatment. She said it was fine :( I suppose all a learning experience for us but I will contact the manufacturer to see if this sort of reaction is possible. Thank you again for taking the time. Much appreciated!
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It's not about a dog bu a ferret. My furbabies received thr red one for dog, (revolution) divided in four, to kinda make a 15mg/kg. Since the application, 1 of them is having trouble breathing, rapid heart rate, bloody mucosis diarhea, and lost of balance. In the first 36h she was like a rag, lifeless. We went to the vet, she got some subcutaneus fluids and meds for gastric ulcerations. She started eating again on her own yesterday ( it's been 12 day today since the application) and all the vets just brush off the idea of toxicity. Its so safe. But i'm treatin the 4 ferrets at the same time, and 2 large dogs too in the same house. Is it possible that she was subjected to a 'sur-exposure/overdose'? If so, how long will it take for the pesticide to leave her body AND the others? Supportive care is been done 100%, i'm changing the beedings daily and cleaning the floors too from any residue that the dogs might leaves.
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