IVERMECTIN IN SMALL ANIMAL DERMATOLOGY - PART-II - EXTRALABEL APPLICATIONS

The only FDA-approved use of ivermectin in small animals is prevention of heartworm disease; however, large-animal formulations are widely u sed in small animal practice to control such parasite problems as ear and nasal mites, scabies, cheyletiellosis, various mange mites, and ge neralized demodicosis in dogs. In small animal dermatology, ivermectin can be used to establish or rule out ectoparasites or endoparasites a s a cause of pruritic dermatitis. Because of the idiosyncratic reactio ns encountered in some dogs, however, it is not reasonable to expect t hat canine (or even feline) ivermectin products will be marketed for u ses other than heartworm prevention. The ivermectin formulation, route of administration, and dose regimen to be used depend on the parasite . To control some parasites, treatment of ail exposed fur-bearing anim als and environmental controls are necessary. The pour-on formulation of ivermectin is effective against some parasites and is easy to admin ister to a large number of animals. Veterinarians should be careful no t to exceed the recommended (extralabel) doses oi an ivermectin formul ation. As with any extralabel drug use, the veterinarian must explain the risks and benefits to the client and ask the owner to sign a relea se form. Collies and related harding-breed dogs tolerate the dose of i vermectin used for heartworm prevention but are susceptible to potenti ally fatal idiosyncratic toxicity reactions if they receive larger dos es. The first part of this two-part presentation (February 1998) consi dered the pharmacology and toxicology or ivermectin in small animal de rmatology; Part ii discusses extralabel uses of ivermectin in this fie ld.