Ivermectin is a drug made by soil living bacteria and acts as a parasiticide. It acts via the GABA (gamma amino butyric acid) nerve centers. GABA is a neurotransmitter. Essentially, this drug works on the GABA by interrupting the transmission of nerve impulses and, by so doing, paralyzes and kills the parasite.
In mammals, most of these medications that involve the GABA nerve centers are screened out by our blood-brain barrier. This screening process makes these medications very safe for use on mammals such as dogs, with some exceptions.
Ivermectin for Dogs – Usages
Ivermectin is approved by the United States Food and Drug Administration (FDA) for use in dogs as a heartworm preventative. It is sold under various brand names such as Heartgard®, Heartgard Plus®, Iverhart®, and others.
Prior to using a heartworm preventative containing ivermectin, the dog should be tested for the presence of heartworms. Dogs who have tested positive for heartworm disease should not use ivermectin except under strict supervision of a veterinarian.
As a heartworm preventative, the medication is usually given orally once a month. The dosage for dogs is 0.0003-0.0066 mg/lb.
In addition, there are some off-label uses of ivermectin, such as using it to kill microfilaria (immature heartworms), to treat mange, and certain intestinal worms.
For these purposes, the dose has to be increased and therefore should be used only under the direct guidance of a veterinarian.
Ivermectin for Dogs – Possible Side Effects
Ivermectin is relatively safe and is considered safe to use in pregnant or nursing dogs with a few exceptions. Side effects are rare due to the blood-brain barrier protective effect, but in some dogs, they may develop dilated pupils and incoordination.
However, dogs with the following conditions should not be prescribed Ivermectin:
- Those who have shown prior allergic reactions to the drug.
- Those who have tested positive for heartworm disease.
In addition, young puppies (under 6 weeks old) should not be given this drug.
Also, many Collies and some of the other “collie-like” breeds (such as Shetland Sheepdogs and Border Collies) have been shown to possess a mutant gene called MDR 1.
This mutation opens up the blood-brain barrier and the use of ivermectin can lead to neurological signs and even death, especially in higher doses.
Due to the low dosages used in heartworm preventatives, many Collies have no problem but to be safe it may be better to use other medications.
If you choose to use ivermectin as a heartworm preventative on your Collie, observe him carefully for about 8 hours after treatment.