What is ivermectin?
Ivermectin is most used as a heartworm preventive in dogs and cats. It also used “off label” or “extra label” for treating a variety of internal and external parasites. For example, in dogs, ivermectin may be used to treat mites (demodectic mange, scabies, and ear mites), intestinal parasites (hookworms, roundworms), and capillaria. In cats, ivermectin may be used to treat ear mites and cat scabies.
Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
How is ivermectin given?
- Ivermectin is available as tablets, chewable tablets, a topical liquid (for ear mite treatments), and an injectable that your veterinarian administers.
- It may be combined with other deworming medications.
- It may be given with or without food. If your animal vomits or acts sick after getting the medication, or after taking the medication on an empty stomach, give with food or a small treat to see if this helps. If vomiting continues, contact your veterinarian.
- Your veterinarian will provide instructions for applying topical ivermectin to your pet's ears.
- Give the medication as directed by your veterinarian.
This medication should take effect within one to two hours; however, effects may not be visibly noticed, and so laboratory tests may be required to evaluate this medication’s effectiveness.
What if I miss giving my pet the medication (or my shipment is late)?
If you miss a dose, give it as soon as you remember, and then wait the amount of time between doses recommended by your veterinarian before giving the next dose. Do not give your dog two doses at once or give extra doses.
If you are using ivermectin as a heartworm preventive and more than eight weeks have passed without giving this medication, contact your veterinarian for guidance.
Are there any potential side effects?
Ivermectin is generally well tolerated at doses used for heartworm prevention. Side effects may occur at higher doses.
If the following side effects occur, contact your veterinarian immediately:
- serious neurological side effects, including stumbling, trembling, dilated pupils drooling or head pressing
- stomach upset, including vomiting and diarrhea
- shock, if ivermectin is killing large numbers of heartworm larvae (signs of shock include weakness, vomiting, diarrhea and pale gums)
This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease. In the case of heartworm prevention, protection will last for four weeks.
Are there any risk factors for this medication?
Ivermectin should NOT BE USED in dogs that:
- are younger than six weeks of age
- do not have a current negative heartworm test
Some breeds of dog (e.g., collies, sheepdogs, and collie- or sheepdog-crosses) are more sensitive to ivermectin than others. This is typically due to a genetic mutation (MDR1) that makes them less able to tolerate high doses of ivermectin and other medications. If used at prescribed doses for heartworm prevention, ivermectin is considered safe for MDR1-affected dogs.
Your veterinarian will advise you on the safety of ivermectin use in your dog. If your dog is a breed likely to be sensitive to the medication and a higher dose is needed for treatment, your veterinarian may recommend genetic testing to see if your dog will tolerate it.
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 before starting any treatment.
Some medications increase the effects of ivermectin in a pet’s brain, including:
- ketoconazole
- itraconazole
- cyclosporine
- erythromycin
- amlodipine besylate
- nifedipine
Spinosad (a common flea preventive treatment) should not be administered when high doses of ivermectin are used to treat mite infestations. Spinosad is safe to use in conjunction with the low doses of ivermectin used in heartworm preventives.
Is any monitoring needed with this medication?
- For dog breeds with potential ivermectin sensitivity, screening may be done before receiving the drug.
- DNA testing can determine whether a pet has the genetic mutation responsible for adverse reactions to ivermectin.
How do I store ivermectin?
Store ivermectin-based products at room temperature in a cool, dry place, away from heat and direct sunlight. Exposure to heat or moisture may reduce the drug’s effectiveness.
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.
