Selamectin Revolution kills adult heartworms microfilarae

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Selamectin Revolution kills adult heartworms microfilarae

Postby malernee » Mon Sep 20, 2004 8:06 am

Selamectin (Revolution), a New Player in the Control of Fleas and Heartworms in Dogs and Cats

Author Dwight Bowman, BA, MS, PhD


Revolution is a new, Federal Drug Administration approved, topically-applied product for the prevention of heartworm disease and the prevention and control of flea infestation in cats. The active ingredient, selamectin, is an avermectin compound that was synthesized and developed by Pfizer Animal Health, Exton, PA. Revolution also has excellent efficacy against the canine and feline ear mite (Otodectes cynotis) and is labeled for the treatment and control of this pathogen. Revolution is the only newly-approved product for the treatment of sarcoptic mange to be labeled as such since the labeling of amitraz (Mitaban). Revolution can also be used to treat intestinal hookworms and roundworms in cats, but the efficacy against intestinal helminths in dogs seems to be less than one would hope. Revolution prevents tick infestation, but in areas with high tick numbers, it is recommended that a mid-month additional treatment with this product be given.


The benefits of Revolution are that it is a single product that prevents flea infestation and heartworm disease, it is a product that can be applied topically, and it is capable of treating ear mite infestation. Many individuals like giving monthly treats to dogs in the form of chewable heartworm prevention, but at the same time, the success of the topically applied flea-control products, imidacloprid (Advantage) and fipronil (Frontline Top Spot) indicate that people also are very happy with spot-on applications when they are efficacious. Thus, it would seem that ultimately, topical application is a mode of administration that is acceptable to clients. Also, the topical application method is a means by which cats can easily be treated. This means that cats are more likely to get the heartworm prevention that they should be receiving in areas of high heartworm prevalence. Finally, the use of selamectin for the treatment of ear mite infestation allows the steady control of this infestation and is an easy means of preventing reintroduction of this problem when new pets are added to a household.

After the application of Revolution, the selamectin passes through the skin. In dogs, the maximum plasma concentration occurs 3 days after administration and the half life of the product is about 11 days. In cats, the maximum plasma concentration occurs in less than a day after application, and the product's half life is about 8 days. Much more of the product becomes bioavailable in cats than in dogs. After administration, the product is distributed to the sebaceous glands where it is readily available to interact with fleas, ticks, and mites.

As selamectin is distributed systemically, it had to be shown to be safe in pregnant and breeding dogs and cats, puppies, and ivermectin-sensitive collies. The topical administration of the product at three times the prescribed dosage rate was administered to pregnant dogs and cats at monthly intervals (or more frequently), and no effect was found on the conception rate, the number of offspring per litter, the number of live births per litter, or the number of weaned animals. Also, in male dogs and cats, no effect was found on the conception rate, and in dogs, no demonstrable effect was found on semen quality. Also, tests were performed in puppies and kittens, in which the product was applied at a dosage as high as 10 times the prescribed dosage beginning at 6 weeks of age for 7 consecutive monthly treatments and, even at these levels, none of the animals developed any treatment-associated signs. The product was tested in ivermectin-sensitive collies at five times the recommended dosage of the topical product without any effects.

Another concern is what would happen if the product was applied to human skin? Humans absorb the compound much like dogs. However, studies indicate that the application of the single largest packaged dose of the product to a human would result in a drug concentration in the human that was more than 250 times below that required for an observable effect. Thus, the product is safe for use by clients. Of course, as with all chemicals, it is a good idea to wash one's hands after applying the product to a dog or cat.

This product was administered at three times the recommended dosage to dogs with heartworm infection without the dogs showing any signs due to death of the microfilariae, which did disappear from the blood. However, the concentration of circulating microfilariae was not remarkably high in the dogs that were treated in this manner (only around 10,000/ml of blood, and some positive dogs can easily have 100,000/ ml of blood). Thus, it is still prudent to follow the label indication to first verify whether or not a dog has circulating microfilariae before initiating treatment with this product.

Revolution appears to be a product that is likely to become a regular part of heartworm and flea control. Pet guardians now have the choice of two products for dogs, Sentinel (milbemycin and lufeneron) and Revolution, for the single-product control of heartworm and fleas in dogs; only Revolution can be used for this purpose in cats.


No one heartworm preventative can easily be said to be better than the next. They all have slightly different characteristics such as mode of treatment and ability to control certain intestinal parasites. The same thing can be said about the new, topically-applied flea products. Revolution, besides being a safe and efficacious product, has the positive characteristics that it controls multiple parasites and can be easily applied to cats, in which it will prevent heartworm and remove the intestinal helminths that could be the cause of zoonotic disease.
From the American Heartworm Society Symposium, April 2001
Dzimianski,McCall The Saftey of Selamectin in Heartworm Infected Dogs and Its effect on Adult Heartworms and Microfilarae, monthly administration of selamectin at the recommended dose is safe in heartworm infected dogs and causes a reduction of adult worms and microfilaria. (A 39% reduction in adults after 18 months.)
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