Selamectin

What is selamectin?

Selamectin (brand names: Revolution®, Paradyne®, Stronghold®, Chanhold®) is an avermectin antiparasitic used topically to treat parasites in dogs and cats.

In dogs, parasites treated by selamectin include fleas, ear mites, scabies, and certain ticks. In cats, parasites treated by selamectin include fleas, ear mites, hookworms, roundworms, and ear mites. Selamectin is also a heartworm preventative in both dogs and cats.

It has also been used to treat nasal mites and cordylobiolosis in dogs, and notoedric mange in cats.

Its use in cats, dogs, and other small mammals to treat certain parasites is off label (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

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 at the base of the neck.
• 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 younger than 6 weeks old or cats younger than 8 weeks old.
• 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.

This medication should take effect within 4 to 8 hours, and will reach full effectiveness within the first week. For dogs, it can take up to 5 days to kill most ticks that are present. Gradual improvements in clinical signs should occur during this time.

What if I miss giving my pet the medication?

• If you use 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 1 and remember on June 18, give the dose on June 18, and start a new monthly schedule. The next dose you give your pet will be on July 18. Do not give your pet two doses at once. Contact your veterinarian if you are concerned about a missed dose.
• If you use selamectin off label, give the dose as soon as you remember, and then wait the recommended time as prescribed by your veterinarian for the next dose. Do not give the pet two doses at once.

Are there any potential side effects?

Side effects are rare, but may include:

• Hair loss at the administration site (cats)
• Loss of appetite, vomiting, diarrhea
• Muscle tremors
• Itchiness
• Redness
• Lethargy
• Salivation
• Increased breathing rate
• Seizures and incoordination (dogs only; rare)

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 WITH CAUTION in:

• Pets that are sick, debilitated, or underweight
• Pets that are pregnant or lactating (precaution)
• Pets that have not been tested for heartworm infection 
• Dog breeds with the MDR1/ABCB1 gene 

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/ABCB1) that makes them less able to tolerate high doses of certain medications. Use selamectin cautiously in these cases.

Are there any drug interactions I should be aware of?

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

Several medications should be used with caution in dogs with the MDR1/ABCB1 genetic mutation when given with selamectin:

• Cyclosporine
• Diltiazem
• Erythromycin
• Itraconazole
• Ketoconazole
• Spironolactone
• Verapamil

Is any monitoring needed with this medication?

• No specific monitoring is needed while your pet is using this medication.
• Your veterinarian may monitor your pet to be sure that the medication is working.
• At home, monitor for any side effects such as those noted above. If any side effects occur, stop using the medication and contact your veterinarian.

How do I store selamectin?

• Store selemectin at temperatures less than 86°F (30°C).
• Keep away from extreme heat or 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. Be prepared to provide information about the product and your pet’s weight and symptoms.