Medication: Ivermectin

Your dog has been prescribed the active ingredient ivermectin for the management of ectoparasitic and endoparasitic infestations including heartworm (Dirofilaria immitis). 

Key points:
• Heartworm preventative.
• Do not give to dogs with MDR1(ABCB1-Δ) gene (eg Collies, Australian Shepherd dogs, Shetland Sheepdogs and related mixed breeds) without first consulting your veterinarian as this drug may cause severe toxicity including death in these breeds.
• All dogs should be tested for existing heartworm infection before starting treatment.
• Dosage: once monthly as preventative year round or during mosquito season or as needed to treat parasites other than heartworm. 

This information sheet is designed to help answer commonly asked questions and help you give the medication safely and effectively to your pet. It does not contain all available information for this medication. If you have other questions or need more information, contact your veterinarian or pharmacist.Always follow the dosing instructions provided by your veterinarian. 

Name

• Ivermectin (I-ver-mec-tin).

Brand name

• Heartgard® (US).
• Heartgard® Plus (ivermectin and pyrantel pamoate) (US).
• Iverhart® (US).

Class of drug

• Macrocyclic lactone.
• Endectocide.

Storage

• Store at <25°C and protect from direct light.

Your veterinarian has prescribed ivermectin as a heartworm preventative – it eliminates the tissue stage of heartworm larvae for a month (30 days) after infection.

Ivermectin may also be prescribed 'off-label' for the management of internal (eg lungworms or hookworms) or external parasites caused by mites (eg demodicosis, sarcoptic mange, cheylietiellosis). It may be combined with other worming treatments.

Ivermectin is given orally as tablets (US). Both unflavored and chewable tablets are available. It may also be given by injection by your veterinarian (UK – authorized for use in farm animals and horses). Oral liquids and pastes designed for use in livestock and horses are too concentrated for use in dogs and may result in death.

Some breeds of dogs (eg Collies, Australian Shepherd dogs, Shetland Sheepdogs and related mixed breeds) are susceptible to the toxic effects of ivermectin and death may occur. Susceptibility has been linked to a mutation of the multiple drug resistance (MDR or ABCB1-Δ ) gene which normally prevents the entry of Ivermectin across the blood-brain barrier.
Depression may be seen in all breeds when used at higher doses. If your dog exhibits any sign of staggering, tremors, difficulty seeing, or seizures following a dose of ivermectin contact your veterinarian immediately. 

The initial dose of ivermectin must be given within a month (30 days) after the dog’s first exposure to mosquitoes. The final dose must be given within a month (30 days) after the dog’s last exposure to mosquitoes. The drug must be given every month during mosquito season, and many veterinarians recommend that it be given year round. If your veterinarian is using ivermectin for other worms or external parasites the therapeutic regimen will be different. 

Dispose of any unused ivermectin safely – don't flush down the toilet or sink. Do not allow ivermectin to enter the watershed as this drug is very toxic to aquatic life. Ask your veterinary team if they take back medication for disposal. Do not save for future use or give to other pets.

If you miss a dose, give the dose as soon as possible but do not double up a dose. Make sure the dose given doesn’t exceed the total recommended amount in any 24-hour period.

If your dog is unwell, contact your veterinarian for advice. 

Ivermectin should only be given to the dog that it has been prescribed for:

• Do not give to dogs with multiple drug resistance gene (MDR1), eg Collies, Australian Shepherd dogs, Shetland Sheepdogs and related mixed breeds.
• Do not give to turtles or fish or any other aquatic species. 
• If accidentally given to other pets, contact your veterinarian for advice.

If accidentally eaten by a human, speak to your primary care physician or poison control center.

Dogs may be screened for ivermectin sensitivity prior to treatment if suspected to have the MDR1 gene.

Further information

If you have any concerns, further information on ivermectin can be found on the package insert and the following websites:

US

• Boehringer Ingelheim Heartgard® Plus (ivermectin/pyrantel).
  • Website: heartgard.com/
  • Product leaflet: heartgard.com/sites/default/files/2022-09/2022_09_13_HG_Plus_PI_BI.pdf.pdf

Always follow the recommended dosage and contact your veterinary team or pharmacist if you have any questions regarding your dog’s medication.