Imidacloprid & Imidacloprid Combinations, Topical
Indications / Actions
Imidacloprid topical solution (Advantage®) is indicated for the treatment of adult and larval stage fleas in dogs and cats. The combination product with permethrin (K9 Advantix®) is indicated for adulticide/larvicide for fleas, to repel and kill ticks, and mosquitoes in dogs only. The product containing pyriproxyfen (Advantage® II) is indicated for the prevention and treatment of all flea stages in dogs and cats and chewing lice in dogs. The canine combination product with moxidectin (Advantage Multi® for Dogs in US and Advocate® in Europe) is indicated for the prevention of heartworm disease, adult fleas, adult and immature hookworms, adult roundworms, and adult whipworms. It has been also used successfully for the treatment of sarcoptic mange, cheyletiellosis, and mild cases of demodicosis. The feline combination product (Advantage Multi® for Cats) is indicated for the prevention of heartworm disease, adult fleas, ear mites, adult and immature hookworms, and adult roundworms. It was shown to be effective for the treatment of feline demodicosis caused by Demodex gatoi at extralabel dosages. It is also approved for use in ferrets.
Imidacloprid’s mechanism of action as an insecticide is to act on nicotinic acetylcholine receptors on the postsynaptic membrane causing CNS impairment and death. Certain insect species are more sensitive to these agents than are mammalian receptors. This is a different mechanism of action than other insecticidal agents (organophosphates, pyrethrins, carbamates, insect growth regulators [IGR’s], and insect development inhibitors [IDI’s]). The manufacturer states that imidacloprid is nonteratogenic, nonhypersensitizing, nonmutagenic, nonallergenic, noncarcinogenic, and nonphotosensitizing. The manufacturer states that, when applied topically, the compound is not absorbed into the bloodstream or internal organs. One combination product for dogs (K9 Advantix®) also contains permethrin, a pyrethroid (synthetic pyrethrin) that will kill and repel ticks and mosquitoes. Permethrin’s insecticidal activity is as a neurotoxin in susceptible species by slowing sodium ions through sodium channels in neuron membranes. Moxidectin is found in combination products (Advantage Multi® for Dogs and Cats) with imidacloprid. Moxidectin is a macrocyclic lactone that binds to the glutamate-gated ion channels specific to parasites, thereby increasing the influx of chloride ions resulting in hyperpolarization of neuronal cells causing paralysis and death.
Suggested Dosages / Use
Refer to the package information for specific instructions on application of imidacloprid products. They are generally administered once monthly; however, extra-label dosages such as once weekly or every other week have been used. While swimming, bathing, and rain do not apparently significantly affect the duration of action, repeated shampooing may require additional treatment(s) before the monthly dosing interval is completed. Do not reapply more often than once weekly for these animals.
Precautions / Adverse Effects
The manufacturer lists the following contraindications for imidacloprid and pyripoxyfen: Do not use in puppies <7 weeks old, dogs weighing <3 lb or kittens <8 weeks old. The manufacturer recommends consulting a veterinarian before using on debilitated, aged, pregnant, or nursing animals or those on medication.
The combination product with permethrin (K9 Advantix® II) must not be used on cats. Use with caution in households with both dogs and cats, particularly if cats are in close contact or will groom dogs in the household.
When used as directed, adverse effects are unlikely. Because the drug is bitter tasting, oral contact may cause excessive salivation. Do not get product in eyes. If eye contact occurs (human or animal), flush well with ophthalmic irrigation solution or water. While gloving is not mandated, it should be encouraged, as contact with skin should be avoided. Wash hands with soap and water after handling. Keep out of reach of children, and do not contaminate feed. Dispose of product carefully (in the trash); the permethrin-containing product is extremely toxic to fish.
Imidacloprid topical solutions are usually well tolerated. Dermal irritation has been reported at the site of application. Hypersalivation, tremors, vomiting, and reduced appetite may occur in cats after oral exposure to Advantage Multi®. Uncommon to rare adverse reactions reported in dogs treated with Advantage Multi® in a field study included pruritus, lethargy, reduced appetite, and hyperactivity.
Overdose / Acute Toxicity
Most problems are seen following oral dosing of topical products. Signs include hypersalivation and vomiting, and oral ulcers have been rarely reported in cats. There were 119 exposures to imidacloprid reported to the ASPCA Animal Poison Control Center (APCC) during 2008-2009. In these cases, 57 were dogs with 25 showing clinical signs, 60 cases were cats in which 42 showed clinical signs; 1 case was a turtle that showed clinical signs; and the remaining case was a lagomorph that showed no clinical signs. Common findings in dogs recorded in decreasing frequency included vomiting, hypersalivation, and trembling. Common findings in cats recorded in decreasing frequency included hypersalivation, vomiting, lethargy, and hiding.