How to Choose the Right Heartworm Prevention for Your Dog

Posted byCaitlinPosted inAnimal Science, Cool Things, Pet Ownership, Veterinary DrugsTags:, , , , , , , , ,
By: Caitlin McAllister

Why Medicate?

Heartworm preventative medications are the only line of defense a dog-owner has against the deadly parasite Dirofilaria immitis commonly known as heartworm. Transmitted by mosquitos, this disease is hard to detect early, and can cause catastrophic damage to an animals heart and lungs, is very expensive to treat, and generally offends the sensibilities of most. In the long run, it is far cheaper to prevent heartworm than it is to treat it, so using heartworm preventatives regularly is highly recommended for most parts of the world.

But there are many different heartworm medications on the market, so how does one decide which one is right for their pet? Do they all work the same? Which is the best one? The answer depends on a number of factors. In this article I break down the different heartworm medications currently available for dogs on the basis of budget, effectiveness, and ease of administration and safety. Of note, heartworm tests should be performed in dogs greater than 7 months of age before administering any of the following medications according to the regulations of your region and your veterinarian’s advice.

1. Revolution

Image From: https://www.zoetispetcare.com/products/revolution

Revolution is a topical antiparasitic that utilizes the active ingredient selamectin. Selamectin is an avermectin class drug, meaning that it is derived in part from the bacterium Streptomyces avermitilis. While clients may sometimes confuse it with ivermectin, a drug of the same classification, these are not the same product. Avermectins work to kill parasites by inhibiting their electrical conduction systems (think of it like a nervous system destroyer of worms and insects). Selamectin is FDA approved for use in pets and has been available and effective for over 20 years. It is typically administered in a dose of no more than 6 mg/kg of body weight.

Effectiveness: Revolution is considered 100% effective at preventing heartworm in dogs, but also has the added benefit of preventing/treating fleas, ear mites, sarcoptic mange, and specifically the American Dog Tick. If you are using Revolution specifically for tick protection there are other products these days which are considered more effective. That being said, Revolution is still a fantastic product delivering excellent quality for money value. If ticks are not a particular concern, or if your dog is vaccinated against Lyme disease, Revolution remains an excellent choice.

Budget: Revolution is priced based on the dosage, meaning that the cost will be more or less depending on your dog’s weight range. It usually retails from less than $100 to around $150 for a 6 month package depending on the retailer which makes it one of the less expensive than most phone plans on a month-month basis.

Administration and Safety: Revolution is easy to administer. It comes in small plastic tubes and is administered once every 30 days. One simply parts the hair on the back of the animal’s neck and squeezes the contents of a single tube onto the skin of the animal. A full box of revolution will last 6 months, and the package even comes with stickers to put on your calendar. While the manufacturer, Zoetis, states on their webpage that gloves are unnecessary for administration, independent research has shown human exposure to Selamectin causes irritation, so use your discretion and flush with water if the substance gets on your skin. If you ever feel ill, seek medical attention as it is possible to be exposed up to 72 hours post administration. That being said, I personally have never had issue when giving my dog her Revolution. In terms of side effects, the company reports hair loss and skin irritation and flaking at the site of administration to be the most common adverse reaction,

Note: Selamectin is not safe to be administered by mouth, always follow your veterinarian’s instructions when giving Revolution.

2. Heartgard

Image from: https://heartgard.com/

Heartgard and Heartgard Plus are manufactured by Boehringer Ingelheim and uses the active ingredient ivermectin, a semi-synthetic avermectin similar to selamectin. Ivermectin is considered highly effective against heartworm, killing both larval and young adult worms.

Effectiveness: Heartgard by itself is a one trick pony. It’s very good at killing heartworm, but not considered effective against much else. Heartgard Plus on the the other hand combines Ivermectin with another anthelminthic pyrimidine drug called Pyrantel which makes it effective against hookworms, roundworms, and tapeworms for a nice well-rounded monthly de-wormer.

Cost: If you’re only concerned about heartworm and intestinal worms then Heartgard Plus is possibly the product for you. You get a 6-month haul of monthly chew tabs that depending on the size of your dog (we have a common theme here) can set you back anywhere from $30-$120 depending on the size of your dog and the degree of markup. Where prices can escalate is if you then need to purchase flea and tick protection separately in the form of Bravecto or some other product. While many of these stand alone products are of excellent quality, if you’re looking to save some money at negligible quality differences, a combo drug like Revolution or NexGard may be the way to go. Most vets stock multiple different products and are happy to recommend alternatives to fit your situation.

Ease of Administration and Safety: Heartgard is an orally administered beef-flavored chewable tablet given once monthly. Some dogs are happy to take it as if it were a treat, other’s give you a withering look of “surely you’re not serious” and so begins a war to open the mouth and force it down or hide it in something delectable. Sadly my pooch seems to fall in the latter category as a beef purist. In terms of side effects, humans should call poison control and seek medical attention if swallowed. Adverse reactions to watch for (while rare) include: vomiting, disinterest in food, diarrhea, difficulty walking or altered gait, convulsions, and enlarged pupils within 24 hours of administration. Call your vet immediately if you suspect your animal is having a reaction.

3. Iverhart Max

https://vet-us.virbac.com/files/live/sites/virbac-b2b-usa/files/client%20leaflet/Products/Iverhart%20Max/New%20IVH%20Max%20Chew_Plus_Sell%20Sheet%20_Final.pdf

Iverhart Max and Iverhart Plus are extremely similar products to Heartgard in that both products use either Ivermectin or Ivermectin/Pyrantel to kill heartworm, hookworm, roundworm and tapeworm. The difference is that Iverhart products are produced by a different company, Virbac. It is similarly a pack of chews, but is typically pork flavored.

Cost: Similar to Heartgard, depends on the markup.

Administration and Safety: Same spiel as for Heartgard.

Why choose Iverhart over Heartgard? Does your dog prefer pork or beef. Which product is your vet currently stocking?

4. NexGard Spectra

Not into topical administration but want a drug that does more than just heartworm? NexGard Spectra might suit your needs. NexGard Spectra has products for weights from 2-30 kg. Unlike Heartgard and Revolution, it uses a combination of 2 different drugs to achieve it’s multi-antiparasitic effects, Milbemycin oxime and Afoxolaner. Afoxolaner is an isoxazoline ectoparasiticide that kills fleas and ticks by disrupting their nervous system while Milbemycin is a macrocyclic lactone that works by paralyzing heartworms and other intestinal nematodes.

Effectiveness: NexGard Spectra is 69-100% effective against heartworm in clinical studies. It’s also protective against fleas, three varieties of tick, demodex (a parasitic skin infection), roundworms, whipworms, and hookworms and flea tapeworm.

Administration and Safety: NexGard Spectra is administered as an oral monthly chewable tab. It is considered reasonably safe with the most commonly reported side effects being vomiting, diarrhea, itchiness, and skin disorders.

Cost: NexGard Spectra may give you the greatest bang for your buck with considerable variability in price from $30-$200 depending on the size of your dog and the retailer. Bear in mind though, that NexGard Spectra is not as effective against heartworm as other products like Heartgard or Revolution.

5. Trifexis

https://yourpetandyou.elanco.com/us/our-products/trifexis

Trifexis is a combo drug made by the company Elanco, and contains the active ingredients Milbemycin and Spinosad. Spinosad is a pediculicide or lice destroying agent. While it is also marketed to humans in the form of hair-lice prevention and as an insecticide, it is important to note that these products are NOT safe to use as a substitute.

Effectiveness: Trifexis is effective against heartworm, hookworm, roundworm, whipworm, and fleas but NOT ticks. This puts it at a distinct disadvantage to other combo products such as NexGard or Revolution when it comes to bargain for your money.

Cost: According to Petco.com a 6 pack of Trifexis can cost between $130-160 . A veterinarian may charge more or less depending on your dog’s weight and the degree of markup.

Administration and Safety: Trifexis is a beef-flavored chew given once every 30 days. While Trifexis is considered safe for most dogs, Collies and Sheepdogs tend to be more sensitive to the active ingredient Milbemycin. Side effects can include vomiting, diarrhea, decreased appetite, trembling, and convulsions and it is not appropriate for lactating dogs due to potential impact on the puppies.

6. Interceptor & Interceptor Plus

https://my.elanco.com/us/interceptor-plus

Interceptor and Interceptor Plus is another combo drug made by the company Elanco, of milbemycin and praziquantel. Praziquantel is an anthelminthic used in many veterinary drugs.

Effectiveness: Interceptor Plus is effective against heartworm, hookworm, roundworm, whipworm, and tapeworms.

Cost: According to VetrxDirect, prices range from $42-108 (USD), which could be higher depending on who you purchase it from. Much like Heartgard, Interceptor has the same pitfall in that, while a perfectly good product, cost of care increases if you need to purchase separate flea and tick preventatives. Online pharmacies do tend to have better prices, but reliability and legality of such options are highly suspect.

Administration and Safety: Interceptor like other heartworm medications is given on a monthly basis in the form of a chew tab. It is considered to be very safe; however some dogs may experience adverse reactions such as vomiting, diarrhea, trouble walking or lack of coordination, and in some cases foaming at the mouth. The company further notes that administration of Interceptor can cause dangerous reactions if an animal is already infected with adult heartworms, underscoring the need for a heart-worm test before giving this drug. If you suspect your animal is experiencing a reaction, call your veterinary clinic immediately. Of note, Interceptor is not appropriate for lactating bitches as it can be passed through the milk and exhibit overdose effects on the puppies.

7. Sentinel and Sentinel Spectrum

https://www.merck-animal-health-usa.com/species/canine/sentinel/sentinel-spectrum-chews

Sentinel and Sentinel Spectrum are made by the drug company Merck (which is also known as MSD outside of the US, Canada, and Puerto Rico). Sentinel is a combination of the active ingredients Milbemycin and Lufenuron, while Sentinel Spectrum adds a third ingredient, Praziquantel.

Effectiveness: The difference between the two is that Sentinel Spectrum has added protection against tapeworms. Both versions protect against heartworm, fleas, hookworm, whipworm, and roundworm. It is indicated for dogs and for puppies as young as 6 weeks of age.

Cost: On sites such as Valley Vet Supply, Sentinel ranges in price from $51-77 USD. Veterinary retailers may charge more or less depending on markup, but it generally runs less expensive for a pack of 6 chews than some other brands.

Administration and Safety: Sentinel and Sentinel Spectrum are considered very safe. One chew is administered once monthly by mouth and in clinical trials had a 96.6% acceptance rate for palatability. In terms of safety Sentinel is well tolerated by most dogs and but side effects have not been teste in pregnant and lactating dogs, and hypersensitivity has been noted in collies and animals with high numbers of microfilariae (baby heart worms). One possible drawback is that with only 4 weight ranges, there is no box of Sentinel for dogs over 100 lbs.

Conclusion

All together, there are many different medications a person can choose when considering heartworm protection. What you choose can depend on price, where you’re located, your animal’s breed, temperament, and overall health. If you’re dog hates any and all forms of oral chews or you simply want something that’s easy to administer Revolution is a popular choice. If you want an oral chew that covers a wide array of parasites, NexGard has you covered. If you want to and can afford to pair some of the best quality de-wormers with other flea and tick medications, consider Heartgard, or Interceptor Plus. Want an affordable combo drug for a dog that weighs less than 100 lbs, Sentinel is there for you. There are many options to choose from, all with their own advantages and drawbacks. As always your best resource is your veterinarian. Talk to them about selecting the best heartworm preventative medication for your dog and their health status.

Want More Content Like This?

If you enjoyed reading this article. Consider leaving a small donation of $1-2 on my patreon. I may be an international student, but unlike other international students I am not from wealthy family. I am struggling to pay for my degree off my own blood, sweat, and tears. While I enjoy writing, it takes time and effort and is not particularly lucrative. Any small donation would be greatly appreciated. That being said, I appreciate everyone who does me the honor of reading my blog. I may not be the most inspiring writer but I am working on myself and seeing that people actually read this stuff makes my day. Whether you donate or not, everyone is welcome at PetiScience, and I thank you for your continued support. Please feel free to leave a comment down below, let me know what you think, and what you’d like to hear about in the future.

-Caitlin McAllister (DVM Candidate 2028).

References

Published by Caitlin

Hi, I'm Caitlin McAllister, author of PetiScience. I hold a BSc. in Animal Biology from the University of Guelph, ON, Canada, and a Master of Animal Bioscience from the same university. I'm currently a Doctor of Veterinary Medicine Student at the University of Nicosia in Cyprus. I also have experience working with animals in a veterinary setting and am currently pursuing graduate studies with the hope of one day becoming a veterinarian. I decided to start PetiScience because I have a passion for animal science, and veterinary medicine, plus I wanted to continue to learn and share the knowledge I've gained with the general public. With my blog, I hope to effectively bridge the divide between the pet owner and the scientific community. As such, I intend to cover topics in basic animal anatomy, diseases, and common practices in the veterinary and agricultural industries. All of my posts will be scientifically informed and referenced for your benefit. I also have several wonderful cats, a dog, and a fish. They may also come up in my blog from time to time. If you have a question you’d like answered or a topic you’d like me to cover please head over to the comments section. Thank you for visiting PetiScience, I hope you enjoy!

Leave a comment