Afoxolaner, the active ingredient in NexGard and NexGard SPECTRA, is part of the isoxazoline family of chemicals. Adverse reactions to this family of chemicals are rarely observed but may include vomiting, diarrhoea, lethargy, inappetence (loss of appetite), itching and very rarely, seizures.
It has minimal side effects, and has been shown to be safe at up to 5 times the recommended dose. In a 90-day field study, 415 dogs were administered afoxolaner and no serious adverse reactions were observed with NexGard. The most frequent adverse reaction was vomiting, with 17 dogs experiencing that reaction.
Thank you for your question. I would not expect the lethargy or diarrhea to last more than 12-24 hours.
Nexgard does sometimes cause a little GI upset or diarrhea, especially if it is not given with food.
If you give your dog or cat the flea and tick preventatives Bravecto, Nexgard, Simparica, or Credelio, the FDA wants you to be aware that these medications may cause neurological issues like stumbling, seizures, and twitching in your pet.
ADVERSE REACTIONS: The following adverse reactions have been reported following the use of HEARTGARD: Depression/lethargy, vomiting, anorexia, diarrhea, mydriasis, ataxia, staggering, convulsions and hypersalivation.
Isoxazoline products have been associated with neurologic adverse reactions, including muscle tremors, ataxia, and seizures in some dogs and cats. Although most dogs and cats haven't had neurologic adverse reactions, seizures may occur in animals without a prior history.
NexGard® and NexGard SPECTRA® kill fleas by over-stimulating their nervous system, which results in uncontrolled activity of their nervous system and death. This occurs within 6-8 hours of product administration.
If a dog vomits within 2 hours of administration of a Nexgard tablet, a new tablet should be given. If vomiting occurs after 2 hours, re-dosing is not necessary. There are no known drug interactions with afoxolaner.
These products are safe to use in the majority of pets, but there are some pets that cannot tolerate the medication (specific liver disorders, pre-existing seizure disorders).
“NexGard (afoxolaner) is one of the isoxazoline class of parasiticides. Please do NOT use any of them again. There are now two isoxazoline-related class-action lawsuits in North America — one in Quebec and the other in New Jersey. The FDA finally has required warnings on the labels and product inserts.
NexGard® Recalls & Controversies
Although there have not been any FDA recalls for NexGuard®, the FDA has put out an alert for pet owners and veterinarians.
Simparica is an excellent choice for flea and tick protection. The monthly chew also comes with an option for heartworm protection, too, as Simparica Trio. But while Simparica is usually safe flea and tick treatment for dogs, it shouldn't be prescribed to dogs with a history of seizures.
NexGard SPECTRA is safe for all breeds of dog when used as directed and can be given to puppies from 8 weeks of age, providing they weigh at least 2 kg.
In the US field study, one dog with a history of seizures experienced a seizure on the same day after receiving the first dose and on the same day after receiving the second dose of NexGard. This dog experienced a third seizure one week after receiving the third dose.
NEXGARD® is recommended for use in dogs and puppies 8 weeks of age and older. FOR ANIMAL USE ONLY. NEXGARD® contains afoxolaner, an insecticide-acaricide for oral treatment and prevention of flea and tick infestations of dogs for one month following a single administration.
Nexgard can kill 99% of all infections in a single treatment. The product kills eggs, larvae, and full-grown parasites making it highly effective in protecting your dog's health.
NexGard SPECTRA provides the most complete protection from fleas, ticks, mites, heartworm and intestinal worms, all in one tasty chew. How often should NexGard SPECTRA be given? You should dose your dog once a month, ideally on the same day of each month.
According to the FDA, some animals receiving drugs in the isoxazoline class, including Bravecto, Nexgard and Simparica have experienced adverse events such as muscle tremors, ataxia, and seizures.
The most common reason is that the fleas are being killed and the dog is no longer being bitten by them. This can cause the dog to feel itchy and uncomfortable, which may lead to restlessness. Additionally, the chemicals in some flea treatments can be irritating to dogs, leading to discomfort and restlessness.
Oral Heartworm Medications
There are rarely side effects, if given at the proper dosage, but some dogs may experience vomiting, diarrhea, or incoordination. In the case of an allergic response to the heartworm medication, a dog may experience itching, hives, swelling of the face, or even seizures or shock.
At elevated doses, sensitive dogs showed adverse reactions which included mydriasis, depression, ataxia, tremors, drooling, paresis, recumbency, excitability, stupor, coma and death. HEARTGARD demonstrated no signs of toxicity at 10 times the recommended dose (60 mcg/kg) in sensitive Collies.
The amount of ivermectin in standard dog heartworm prevention is not likely to cause an emergency in non-sensitive dog breeds if they consumed 1-2 tablets above their normal dosage. However, ingesting a large number of tablets or medication intended for a larger animal may be a concern for your dog.
The medicine in the treatment (Immiticide) can cause a lot of inflammation at the injection site. This can occur no matter how smoothly things go and how little it seems to bother the dog at the time. This can range from being absolutely undetectable to a dog that is crying constantly with pain.