Ivermectin is a common anti-parasitic medication discovered in 1975 by Satoshi Ōmura whose research group isolated the bacterium Streptomyces avermitilis from a single Japanese soil sample near a golf course outside Tokyo. These bacteria produce active fermentation extracts called avermectin. Parasitology specialist William C. Campbell was able to develop ivermectin from avermectin. In 1981 ivermectin became commercialised as a veterinary treatment and was approved for human use in 1987.
Ivermectin is used in both human and animal medicine in the treatment and prevention of a number of external and internal parasites. The drug works by stimulating excessive release of neurotransmitters in the peripheral nervous system of parasite which causes paralysis and eventual death.
The FDA has approved the use of ivermectin as a heartworm preventative in cats and also allow the extra-label use in the treatment for a number of additional parasites. Extra-label means the drug is being used to treat a condition for which it has not been approved.
Ivermectin is metabolised by the liver and excreted out of the body via the feces.
Parasites treated with Ivermectin
IN addition to heartworm prevention, Ivermectin is used to treat the following parasites:
- Topical (spot-on)
- Ear drops
Dosage regimens vary, depending on the parasite treated and the method of delivery. Ivermectin is administered orally, subcutaneously (injection under the skin) or topically (applied to the skin).
- Heartworm- 0.0.24 mg/kg every 30-45 days
- Hookworms – 0.2 mg/kg
- Roundworms – 0.3 mg/kg
- Scabies – 0.2 mg/kg every 7 days for 6-8 weeks
- Ear mites (Otodectes cynotis) – 0.2-0.4 mg/kg, repeat in two weeks
- Hookworm – 0.01 mg/kg
- Lungworm – 0.4 mg/kg
- Roundworm – 0.2-0.3 mg/kg
- Walking dandruff – 0.3 mg/kg, repeat in 35 days
- Demodex mite – 0.3 mg/kg once a week for 3 weeks
- Ear mites (otodectes cynotis) – 0.2-0.4mg/kg
- Scabies – 0.2-0.4 mg/kg, repeat in two weeks if needed
- Roundworm – 0.5 mg/kg, 2-4 treatments with 14 days interval
- Walking dandruff – 0.5 mg/kg, 3 treatments with 14 days interval
- Ear mites – 0.5 mg/kg, repeat in two weeks until the infection clears
Do not use in cats with a known allergy or sensitivity to ivermectin.
Speak to your veterinarian before you administer ivermectin if your cat:
- has reduced liver function
- is pregnant or lactating
- is on wafarin
- has not been tested for heartworm
Can ivermectin be used on pregnant and lactating cats?
Yes, although we always recommend you speak to a veterinarian before administering any medication (prescribed or over the counter) in a pregnant or lactating cat.
What age is it safe to use ivermectin on kittens?
The minimum age is 6 weeks and older.
In healthy cats, ivermectin has a high margin of safety. Overdose can occur when pet owners administer ivermectin products for livestock on their cat in an attempt to save money.
Clinical signs can develop in cats exposed at greater levels than 2.5 mg per kg although toxicosis has been reported in cats at a dose of 0.3-0.4 mg/kg subcutaneously. A cumulative effect can develop in cats who receive several doses. Acute symptoms develop within ten hours of ingestion.
If you suspect your cat has been exposed to ivermectin at a higher than recommended dose, seek urgent medical advise.
- Enlarged pupils
- Head pressing
- Rear limb weakness
- Respiratory depression
Treatment depends on the mode of exposure.
For cats who have recently ingested ivermectin, induce vomiting and administer activated charcoal to prevent further absorption. Unfortunately as symptoms can often develop hours after exposure, this first-line treatment is often ineffective.
Supportive care which will include fluid therapy and nutritional support will also be provided while your cat recovers.
Propofol or diazepam can be given to control seizures.