Safety of selamectin in dogs

Selamectin is a broad-spectrum avermectin endectocide for treatment and con trol of canine parasites. The objective of these studies was to evaluate th e clinical safety of selamectin for topical use in dogs 6 weeks of age and older, including breeding animals, avermectin-sensitive Collies, and heartw orm-positive animals. The margin of safety was evaluated in Beagles, which were 6 weeks old at study initiation. Reproductive, heartworm-positive, and oral safety studies were conducted in mature Beagles. Safety in Collies wa s evaluated in avermectin-sensitive, adult rough-coated Collies. Studies we re designed to measure the safety of selamectin at the recommended dosage r ange of 6-12 mg kg(-1) of body weight. Endpoints included clinical examinat ions, clinical pathology, gross and microscopic pathology, and reproductive indices. Selected variables in the margin of safety and reproductive safet y studies were subjected to statistical analyses. Pups received large doses of selamectin at the beginning of the margin of safety study when they wer e 6 weeks of age and at their lowest body weight, yet displayed no clinical or pathologic evidence of toxicosis, Similarly, selamectin had no adverse effects on reproduction in adult male and female dogs. There were no advers e effects in avermectin-sensitive Collies or in heartworm-positive dogs. Or al administration of the topical formulation caused no adverse effects. Sel amectin is safe for topical use on dogs at the recommended minimum dosage o f 6 mg kg(-1) (6-12 mg kg(-1)) monthly starting at 6 weeks of age, and incl uding dogs of reproducing age, avermectin-sensitive Collies, and heartworm- positive dogs. (C) 2000 Elsevier Science B.V. All rights reserved.