Pyrantel pamoate paste (19.13% w/w pyrantel base) for the treatment of Anoplocephala spp tapeworms was evaluated for safety and tolerance in horses treated orally at 0, 1, 3, 5, and 10 times the clinical dose of 13.2 mg pyrantel base/kg bodyweight administered daily for six consecutive days. Parameters evaluated included clinical signs, food and water consumption, bodyweights, physical examinations, clinical pathology (hematology, coagulation, serum chemistry, urinalyses, and fecal examinations), complete necropsy, organ weights, and histopathology. No adverse events or test article-related effects were observed in any treatment group during daily clinical observations of the test animals. Statistically significant changes (P < .05) lacked a dose- and/or time-dependent trend and were considered incidental. Administration of pyrantel pamoate paste did not produce any macroscopic or microscopic tissue effects in any dose group of either sex. The no-observed-effect-level (NOEL) for pyrantel pamoate paste, when administered orally to horses once daily for 6 consecutive days, was determined to be 132 mg/kg/day. Pyrantel pamoate paste (19.13% w/w pyrantel base) can be safely administered orally to horses at 13.2 mg of pyrantel base/kg for the treatment of Anoplocephala infestations.
