Selamectin

By Rania Gollakner, BS, DVM

Medications

What is selamectin?

Selamectin (brand names: Revolution®, Paradyne®, Stronghold®, Chanhold®) is an avermectin antiparasitic used topically to treat parasites in dogs and cats. When used in dogs, parasites treated by selamectin include fleas, heartworms, ear mites, scabies, and certain ticks. When used in cats, parasites treated by selamectin include fleas, heartworms, ear mites, hookworms, and roundworms, with some possible effectiveness against ear mites. It has also been used to treat notoedric mange, nasal mites, and cordylobiolosis.

Its use in cats, dogs, and other small mammals to treat certain parasites is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their direction may be significantly different from those on the label.

How quickly does it kill fleas and ticks?

Fleas will start dying in the first 4 to 8 hours, but it can take several days before the medication reaches its full effectiveness against fleas. For dogs, it can take up to 5 days to kill most ticks that are present.

How is selamectin given?

Selamectin is applied topically by parting the hair and applying the entire contents of the tube directly to dry, unbroken skin. Once applied to the skin, avoid massaging the medication into the skin or touching the application site while it is wet. In dogs, do not bathe within 2 hours of application. In cats, do not bathe within the first 24 hours of application. Do not apply to dogs less than 6 weeks old or cats less than 8 weeks old. This medication should take effect within 4 to 8 hours, and will reach full effectiveness within the first week. Gradual improvements in clinical signs should occur during this time.

Avoid contact with human skin; if it occurs, wash the skin immediately and thoroughly. Wear gloves or wash your hands after applying selamectin. Do not expose this medication to fire as it is flammable.

What if I forget to give my dog/cat/pet the medication, or my shipment is late?

If using selamectin once monthly, give the dose as soon as you remember and start a new monthly dosing schedule. For example, if you forgot to give your pet his/her dose on June 1st and remember on June 18th, give the dose on June 18th and start a new monthly schedule. The next dose your pet will receive would be on July 18th. Do not give your pet two doses at once. Contact your veterinarian if you are concerned about a missed dose.

If using selamectin off label, give the missed dose as soon as you remember, and then wait the recommended amount of time between doses. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects are rare. A small percentage of cats may develop hair loss at the administration site. Other rare side effects include loss of appetite, vomiting, diarrhea, muscle tremors, itchiness, redness, lethargy, salivation, and increased breathing rate. In dogs, seizures and incoordination have been rarely reported.

This long-acting medication may last up to 4 – 6 weeks, and may last longer in pets with kidney or liver disease.

Are there any risk factors for this medication?

Use cautiously in sick, debilitated, or underweight pets. This medication appears safe to use in pregnant and lactating pets, but as a precaution use carefully in these cases. Selamectin should be used cautiously in pets that have not been tested for heartworm infection.

Some breeds of dogs (e.g., collies, sheepdogs, and collie- or sheepdog-cross breeds) are more sensitive than others to medications. This is typically due to a specific genetic mutation (MDR1) that makes them less able to tolerate high doses of certain medications. Therefore, selamectin should be used cautiously with these breeds of dogs.

Are there any drug interactions I should be aware of?

The following medications should be used with caution in dogs with the MDR1 genetic mutation when given with selamectin: amiodarone, carvedilol, clarithromycin, cyclosporine, diltiazem, erythromycin, itraconazole, ketoconazole, quinidine, spironolactone, tamoxifen, and verapamil.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working.

How do I store selamectin?

Selemectin should be stored at temperatures less than 30°C (86°F). Be sure to keep away from extreme heat or an open flame as this medication is flammable.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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