A Supplement to Compendium on Continuing Education for the Practicing Veterinarian

The objective of the study was to evaluate itchingoccasionally observed in cats and dogs shortly afteradministration of nitenpyram(Capstar; NovartisAG, Basel, Switzerland).Twelve cats and twelve dogs were caged individual-ly, infested with 100 fleas, and dosed with niten-pyram 24 hours later. Cats and dogs were dosed withtablets containing 11.4 mg and 57.0 mg nitenpyram,respectively. Dead fleas began falling off the treatedanimals within 15 to 30 minutes and were collectedin pans placed in the bottom of the animals’ cages for8 hours after administration of nitenpyram. All catsand dogs were observed for signs of itching for 3hours after treatment. These signs of itching werecompared with data obtained when the same cats anddogs were infested with fleas but not treated; or weretreated with nitenpyram in the absence of fleas.Number and duration of itching episodes were as-sessed by videotaping the animals.The results indicate that the cause of itching wasthe presence of fleas affected by nitenpyram and thatthe degree of itching was highly dependent on theindividual dog or cat. Treatment with nitenpyramresulted in high numbers of fleas showing increasedactivity before dying and falling off the host 1 to 2hours after treatment. During this period, a three-fold to sixfold increase in flea-related itching was ob-served in cats and dogs when compared with un-treated flea-infested animals.