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92 PRACTICAL PARASITOLOGY PEER REVIEWED NEONICOTINOIDS This class of agents acts by binding to insect acetylcholine receptor sites. 1 This induces inhibition of insect nervous system function, with subsequent paralysis and death. Imidacloprid This product has a rapid onset of action. 10,11 It primarily targets adult fleas, and it is often combined with an insect growth regulator to provide efficacy against immature flea stages. 1 Imidacloprid is available as a spot-on product, either by itself or in combination with permethrin (K9 Advantix), flumethrin (Seresto collar; seresto.com ), or moxidectin (Advantage Multi; bayerdvm.com ). Imidacloprid is generally very well tolerated by most individuals. Products containing imidacloprid alone (or imidacloprid/insect growth regulator alone) can be applied up to once weekly for aggressive flea control. 1 In my experience, imidacloprid has poor water resistance and must be reapplied after bathing or water immersion. The imidacloprid/flumethrin collar appears to replenish the product on the pet, making this product better suited for patients that are bathed or swim regularly. 12 However, this does shorten the expected lifespan of the collar. The efficacy of the collar is generally very good, which represents a substantial improvement over most older flea collars (typically containing organophosphates), which demonstrated low efficacy. 13,14 Nitenpyram This agent is available as a nonflavored oral tablet (Capstar). It has a very rapid onset of activity against adult fleas but a short duration of action (approximately 24 to 48 hours). 1 Because of the speed of onset, it is well suited for rapid decontamination of animals before or after hospitalization or boarding or after trips to areas such as dog parks. The short duration of action makes it poorly suited for use as a primary flea control agent, but it can be used as often as daily if desired. 1 For this reason, it is sometimes used daily for a short period to get a "head start" on flea depopulation in heavily contaminated environments. It has no larvicidal or ovicidal properties. 1 Dinotefuran This agent is primarily active against adult fleas. 1 It is available in a spot-on formulation in combination with an insect growth regulator either with (Vectra 3D) or without (Vectra) permethrin. It is labeled for application once monthly. This agent has moderate to good resistance to water, although it is suggested that the pet not be bathed or allowed to swim for several hours after application. 15 Nonetheless, it is probably not ideal for a dog that swims or is bathed very frequently. Spinosad/Spinetoram These two products are closely related. Spinosad is a naturally occurring mixture of spinosyns A and D, which are produced by Saccharopolyspora spinosa, a soil-dwelling actinomycete bacterium. 16 It is available as a flavored (pork) tablet. It should be given with food. 16 The same formulation (Comfortis; comfortis.com ) is used in cats and dogs, although the feline version reflects the need for a higher dose per body weight than in dogs (50 mg/kg vs 30 mg/kg, respectively). It is labeled for once-monthly administration. The major side effect in both species is vomiting, which can be treatment limiting in some individuals. 16 Spinosad should be administered with caution (or avoided entirely) in dogs with preexisting seizure disorders because seizures have been associated with administration of this drug in these dogs. 16 However, this effect has not been reported in cats. Spinosad should not be given with extralabel doses of ivermectin because coadministration has been associated with seizures, ataxia, twitching, and other neurologic signs. 16 Spinetoram is a semisynthetic insecticide produced by chemical modification of the naturally occurring spinosyns J and L. 17 It is labeled for use in cats only (Cheristin; cheristin4cats.com ). 18 It is provided as a spot-on formulation, which may be easier for some clients to administer than oral tablets. It is normally well tolerated, although it may be associated with vomiting in some cats. Application- site dermatitis has been reported, although this is less common than with the older formulation. 18,19