Ivermectin for Dogs

What is ivermectin used for in dogs

Ivermectin (EYE-ver-MEK-tin) is an anti-parasitic medication, and a relatively new animal drug ^[3], prescribed for preventing heartworm diseases and treating other conditions like ear mites, and sarcoptic and demodectic mange in dogs ^[1]. It may also be used for controlling parasites affecting other external or internal organs like the intestines ^[2].

Is ivermectin safe for dogs

Whether the drug may be safely tolerated depends on the amount of dosage administered ^[4]. The FDA has approved its use for the management of ear mites, as well as for prevention of heartworm diseases (in dogs that are free of the adult parasites) ^{[4, 14]}, as these uses involve moderate dosages ^{[1, 3]}.

The doses in all other off-label uses of Ivermectin may be 50 times higher ^[1], which may increase the risks of toxic effects and complications ^[4].

If ivermectin is given to dogs with a pre-existing heartworm disease, a shock-like reaction, believed to be caused by the sudden death of heartworm larvae (microfilariae) ^[12], may occur ^[4]. This is why it is only recommended for preventing heartworm, and not treating it.

Quick Information
	Generic name (active ingredient): Ivermectin [2] Brand names: Heartgard®, Iverhart ® (in combination with pyrantel pamoate) [2] Type: Anthelmintic class of drugs [6] FDA approved: Only in dogs [1] Availability: On prescription [2] Who can take it: Dogs [1] Available forms: 68 μg, 136 μg, and 272 μg flavored/unflavored chewable tablets [2]; 2.7 mg/ml and 10 mg/ml injectable; 10 mg/ml oral liquid

How does ivermectin work in dogs

Ivermectin, with its anti-parasitic property, disables the normal nervous system functioning of the heartworm larva at different stages of development ^[14], and other disease-causing parasitic mites ^{[6, 15]}. It causes neurological damage to the parasites and heartworm microfilaria, resulting in their paralysis and death ^[1].

Dosage: how much ivermectin to give your dog

Follow your vet’s dosage instructions, which may vary from one breed to another depending on the dog’s weight and the purpose of the treatment ^{[2, 8]}. The typical dosing information is as follows:

Use	Dosage
Heartworm prevention	0.0015-0.003 mg/lb given once a month [2]
Controlling skin parasites (e.g., mites that cause mange)	0.15 mg/lb given once in 2 weeks [2]
Managing gastrointestinal parasites	0.1 mg/lb given once [2]

The duration of the medication generally depends on the severity of the condition, your dog’s response to the drug, and the occurrence of adverse effects ^{[2, 8]}.

Before prescribing the drug for preventing heartworm, your dog will be tested for the presence of adult worms first ^[2]. If it tests positive, the heartworms are first eliminated using other suitable medicines ^[12]. Then, ivermectin may be administered to prevent further development of the parasite, keeping the dog under medical observation for a minimum of 8 hours after administration ^[4].

Since the tablets are intended to be chewed, you may split it into pieces to keep your dog from swallowing it whole ^[9].

Possible side effects

Low doses of ivermectin usually do not cause any serious side effects ^[10]. The following effects may occur with higher doses:

• Muscle tremors, inability to stand, or difficulty controlling voluntary muscle movements ^[4]
• Dehydration (your dog having dry gums and nose, breathing quickly, losing skin elasticity) ^[4]
• Dilated pupil ^[4]
• Drooling, vomiting ^[4]
• Lack of appetite or anorexia ^[4]
• Lethargy (your dog less interested in going for walks, participating in activities, or playing) ^[4]

Aside from the side effects experienced due to higher doses, multi-drug sensitive dogs may show additional symptoms of Ivermectin poisoning including depression, slow heartbeat, blindness, disorientation, and respiratory distress syndrome ^[10].

If you observe any of these adverse effects in your dog, contact your veterinarian or the ASPCA APCC (Animal Poison Control Center) Helpline 1-888-426-4435 immediately.

Dogs at risk for ivermectin poisoning

• Breeds with multi-drug sensitivity (caused by a mutation in MDR1 gene) like Silken Windhound, Long-haired Whippet, Border Collie, smooth-coated Collies, Australian shepherd, and associated crosses ^[1] (In these breeds, Ivermectin toxicity may be induced at lower doses of around 0.045 mg/lb (100 μg/kg) ^{[1, 13]}, whereas, it takes high doses of over 0.9 mg/lb ^[13] (2000 μg/kg) to cause toxicosis in non-sensitive breeds ^[1]).
• Those exposed to ivermectin-containing medicines meant for treating livestock animals like cows, pigs, and horses ^[1]
• Those living in a rural setting or on farms, where they are more likely to come in contact with the feces of cows, horses, and pigs treated with the medicine ^[1].

When not to give Ivermectin to your dog

Let the vet know your dog’s age, and if it suffers from any health conditions. Ivermectin may not be prescribed to young dogs that do not have a fully developed blood-brain barrier ^[1] (an important layer in the brain composed of endothelial cells managing the passage of molecules and ions from the bloodstream) ^[5].

Also, inform him about any medicines you are giving to your dog. Ivermectin may cause drug interactions if used along with sedatives like Amitraz dips or Valium ^[11].