Affiliate Disclosure: This page contains affiliate links. We may earn a commission if you purchase through these links, at no additional cost to you. Our rankings are based on independent research, clinical data, and editorial criteria — never commission rates.
Medical Disclaimer: NME is not a veterinarian. Heartworm preventives are prescription medications and require veterinary evaluation. Never start or restart heartworm prevention in a dog without a current negative heartworm test first; giving prevention to an already-infected dog can trigger a dangerous reaction, and treating an active infection requires an entirely different protocol. None of the products on this page kill adult heartworms; they only prevent the larval stage from maturing. There is currently no approved treatment for heartworm disease in cats, which makes consistent monthly prevention the only real protection for feline patients. Collies, Australian Shepherds, and related herding breeds can carry the MDR1/ABCB1 gene mutation, which affects how they process certain antiparasitic drugs; discuss breed-specific screening with your vet before starting any product on this page.
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What This Guide Covers
Most heartworm guides just list brand names. That leaves out why a negative test is non-negotiable before starting prevention, why cats face a genuinely different risk calculus since no treatment exists for them, and why a Collie’s genetics can change which product is actually safest.
This guide covers every format — monthly chewables, topicals, all-in-one combos, injectables, and cat-specific formulas — with verified picks and direct links. Nothing on this page was ranked because of its commission rate, and nothing here replaces a conversation with your veterinarian.
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Monthly Chewables (Dogs)
All FDA-approved oral preventives are highly effective against the larval stage of heartworm when given correctly. The real differentiation is what other parasites each one also covers, and whether your dog will actually accept it.
💉 Monthly Chewable Picks
1
Heartgard Plus · ⭐ Top Pick
Heartgard Plus Chewables
Ivermectin + Pyrantel · Monthly · Rx Required · WORLD PET EXPRESS
Combines ivermectin with pyrantel pamoate for heartworm plus roundworm and hookworm coverage in a beef-flavored monthly chew. A trusted formula with a long track record, clinically shown safe for Collies at proper doses, though genetic screening is still worth discussing.
2
Iverhart · Budget Standard
Iverhart Chewables
Ivermectin-Based Generic · Rx Required · WORLD PET EXPRESS
Another ivermectin-based generic option alongside Tri-Heart Plus, a reasonable lower-cost alternative to brand-name Heartgard for straightforward heartworm and intestinal parasite coverage.
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Topical (Dogs)
A topical eliminates the challenge of getting a pill into a dog who won’t take chews willingly, applied directly to the skin once a month.
💧 Topical Picks
3
Advantage Multi · ⭐ Top Pick
Advantage Multi Topical
Moxidectin + Imidacloprid · Rx Required · WORLD PET EXPRESS
Combines heartworm prevention with flea treatment and intestinal parasite control in one topical application, a named top recommendation among vet panels for owners who prefer topical over oral administration.
4
Revolution · Multi-Parasite Standard
Revolution Topical for Dogs
Selamectin · Rx Required · WORLD PET EXPRESS
A well-tolerated topical that consistently works and is generally easy for dogs to tolerate, covering heartworm prevention alongside broader parasite protection in a single monthly application.
5
Selarid · Affordable Alternative
Selarid Topical Solution
Selamectin Generic · Rx Required · WORLD PET EXPRESS
A generic selamectin topical offering an affordable alternative to Revolution, covering heartworm prevention plus fleas and ear mites in the same monthly application format.
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All-in-One Combos
A single monthly product covering heartworm, fleas, ticks, and intestinal parasites simplifies a routine that would otherwise require multiple separate products and dosing schedules.
✨ All-in-One Combo Picks
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Simparica Trio · ⭐ Top Pick
Simparica Trio
Heartworm + Fleas + 5 Tick Species + Worms · Rx Required · WORLD PET EXPRESS
Combines moxidectin’s stronger tissue penetration with sarolaner for fleas and five tick species, plus pyrantel pamoate for roundworms and hookworms, all in one monthly chewable that covers nearly everything most dogs need.
7
Trifexis · Flea-Focused Combo
Trifexis
Heartworm + Fleas + Intestinal Parasites · Rx Required · WORLD PET EXPRESS
Combines spinosad and milbemycin oxime for flea, heartworm, and intestinal parasite coverage in one monthly chewable. Some dogs can smell it and refuse to eat it, worth testing before committing to a larger supply.
8
Credelio Quattro · Newest 6-in-1
Credelio Quattro
Heartworm + Fleas + Ticks + Worms · Rx Required · WORLD PET EXPRESS
A newer approved combination cited as the fastest-growing choice in this category for its 6-in-1 coverage, worth asking your vet about if you want the newest formulation on the market.
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Injectable (Long-Acting)
Injectable options remove the compliance problem entirely, since owner adherence to 12 monthly doses is inherently imperfect. Administered by a veterinarian, these still require a current negative heartworm test beforehand.
💉 Injectable Picks
9
ProHeart 12 · ⭐ Top Pick
ProHeart 12 Injection
Full 12-Month Protection in One Injection · Vet-Administered · WORLD PET EXPRESS
The only FDA-approved product providing a full 12 months of heartworm protection from a single injection, administered by your veterinarian. Compliance studies found injectable moxidectin delivers meaningfully better real-world protection than monthly pills precisely because it removes the risk of a missed dose.
10
ProHeart 6 · 6-Month Standard
ProHeart 6 Injection
6-Month Protection Per Injection · Vet-Administered · WORLD PET EXPRESS
A shorter-duration injectable alternative to ProHeart 12, still eliminating monthly compliance risk while requiring a follow-up visit twice a year rather than annually.
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Cat-Specific
There is no approved treatment for heartworm in cats, and diagnosis is genuinely more difficult than in dogs. This makes consistent monthly prevention the only meaningful protection, for indoor cats too.
🐈 Cat-Specific Picks
11
Revolution Plus · ⭐ Top Pick
Revolution Plus for Cats
7-in-1 Protection · 100% Effective in Trials · Rx Required · WORLD PET EXPRESS
The most prescribed parasite preventative for cats, 100% effective in preventing heartworm disease across two clinical studies. Covers fleas, four tick species, ear mites, roundworms, and hookworms in one monthly topical for cats and kittens 8 weeks and older.
12
Heartgard for Cats · Straightforward Standard
Heartgard for Cats
Ivermectin Chewable · Rx Required · WORLD PET EXPRESS
A straightforward chewable heartworm-only preventative for cats, a reasonable choice for an owner who wants heartworm coverage without bundling in additional flea or tick protection.
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Interceptor for Cats · Broad Intestinal Coverage
Interceptor for Cats
Milbemycin Oxime · Rx Required · WORLD PET EXPRESS
Covers adult roundworm and whipworm removal alongside adult hookworm control and heartworm prevention, safe for kittens in a chewable format some cats tolerate better than a topical.
14
Advantage Multi · Combo Topical
Advantage Multi for Cats
Moxidectin + Imidacloprid · Rx Required · WORLD PET EXPRESS
Combines heartworm prevention with flea treatment, ear mite control, and intestinal parasite coverage in one topical solution for cats and kittens.
15
Centragard · Large Cat Standard
Centragard for Large Cats
Heartworm + Roundworm + Hookworm + Tapeworm · Rx Required · WORLD PET EXPRESS
A topical solution specifically sized for larger cats between 5.6 and 16.5 pounds, covering heartworms alongside roundworms, hookworms, and tapeworms in one monthly application.
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Generic & Budget Options
Generic equivalents contain the same active ingredients as their brand-name counterparts at a meaningfully lower price, a straightforward way to reduce cost without compromising protection.
💰 Generic & Budget Picks
16
Tri-Heart Plus · ⭐ Top Pick
Tri-Heart Plus (Repeat Standard)
Same as Heartgard Plus · ~20% Cheaper · Rx Required · WORLD PET EXPRESS
The most straightforward swap for a lower price without changing the active ingredients, effective against the same parasites as brand-name Heartgard Plus.
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Selarid · Topical Generic
Selarid (Repeat Standard)
Generic Selamectin · Rx Required · WORLD PET EXPRESS
A generic topical alternative to Revolution at a lower price point, covering the same core parasites for owners who prefer topical administration on a budget.
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Generic Ivermectin Chewable
Generic Ivermectin Chewable
Basic Heartworm-Only Coverage · Rx Required · WORLD PET EXPRESS
Covers heartworm prevention alone at the most accessible price point in this category, a reasonable option for an owner already using separate flea and intestinal parasite products.
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Breed-Sensitive Safe
Collies, Australian Shepherds, and related herding breeds can carry the MDR1/ABCB1 gene mutation, which affects drug processing. Milbemycin-based products generally carry a higher safety margin than ivermectin in these breeds.
🦠 Breed-Sensitive Safe Picks
19
Interceptor Plus · ⭐ Top Pick
Interceptor Plus (Breed-Sensitive Standard)
Milbemycin Oxime · Higher Safety Margin for MDR1 · Rx Required · WORLD PET EXPRESS
Milbemycin oxime is considered a safer choice for MDR1-sensitive breeds because it carries a higher safety margin than ivermectin at higher doses, worth discussing specifically if you own a Collie, Australian Shepherd, or related breed.
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Sentinel Spectrum · Broad Milbemycin Standard
Sentinel Spectrum (Breed-Sensitive Standard)
Milbemycin Oxime Base · Rx Required · WORLD PET EXPRESS
Shares the same milbemycin oxime base as Interceptor Plus, adding broader intestinal parasite coverage for herding-breed households that also want comprehensive worm protection.
21
Heartgard Plus · Clinically Tested for Collies
Heartgard Plus (Collie-Tested Standard)
Low-Dose Ivermectin · Rx Required · WORLD PET EXPRESS
Clinical trials have proven Heartgard’s low ivermectin dose safe for Collies when given at the proper dose, a reasonable option if your vet has confirmed the specific dosing is appropriate for your dog’s genetics.
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Health-Condition Specific
Dogs with liver disease, on long-term steroids, or undergoing chemotherapy have specific considerations for which heartworm product and timing is safest. Always coordinate with your vet or specialist.
🎭 Health-Condition Specific Picks
22
Interceptor Plus · ⭐ Top Pick for Liver Disease
Interceptor Plus (Liver-Safe Standard)
Milbemycin-Based & Generally Safer for Compromised Liver Function · Rx Required · WORLD PET EXPRESS
Ivermectin and moxidectin-based products are processed through the liver and can accumulate in dogs with compromised hepatic function. Milbemycin-based Interceptor Plus is generally considered a safer choice for these dogs, though a vet should always confirm before dosing.
23
Sentinel Spectrum · Steroid-Compatible Standard
Sentinel Spectrum (Steroid-Compatible)
Broad-Spectrum Intestinal Coverage for Immunosuppressed Dogs · Rx Required · WORLD PET EXPRESS
Dogs on long-term steroids have suppressed immune response, which can let dormant intestinal parasites reactivate. Broad-spectrum coverage from Sentinel Spectrum is preferable over basic ivermectin-only products in these cases, with annual heartworm testing considered non-negotiable.
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Interceptor Plus · Chemotherapy Timing
Interceptor Plus (Oncology-Preferred)
Commonly Preferred in Oncology Settings · Rx Required · WORLD PET EXPRESS
Commonly preferred for dogs undergoing chemotherapy, administered midway between chemo cycles rather than immediately before or after treatment. Always coordinate timing with both your oncologist and primary veterinarian.
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Multi-Pet Households
A household with both dogs and cats needs coordinated prevention across species, since heartworm medication formulated for dogs cannot be used in cats.
🐕 Multi-Pet Household Picks
25
Sentinel Spectrum · ⭐ Top Pick for Dogs
Sentinel Spectrum (Multi-Pet Standard)
Covers Fleas + Heartworm + Intestinal Parasites · Rx Required · WORLD PET EXPRESS
A top choice for multi-pet households since it controls fleas by halting the life cycle in addition to heartworm and intestinal parasite prevention, reducing the risk of fleas spreading quickly between animals.
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Interceptor · Cross-Species Standard
Interceptor (Dog & Cat Compatible Line)
Same Active Ingredient, Species-Specific Dosing · Rx Required · WORLD PET EXPRESS
Available in formulations for both dogs and cats with the same active ingredient dosed appropriately per species, simplifying which brand a multi-pet household needs to keep track of, though dosing must never be shared across species.
27
Revolution · Dog & Cat Line
Revolution (Dog & Cat Compatible Line)
Species-Specific Formulas Under One Brand · Rx Required · WORLD PET EXPRESS
Offers both dog and cat versions under the same trusted brand name, a reasonable simplification for a household managing prevention across multiple pets and species.
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Puppy & Kitten Safe
Puppies can typically start heartworm prevention earlier than adult dogs based on the specific product label, then be tested later once old enough for an accurate result.
🐶 Puppy & Kitten Safe Picks
28
Interceptor Plus · ⭐ Top Pick
Interceptor Plus (Puppy Formula)
Approved from 4 Weeks & 2 Pounds · Rx Required · WORLD PET EXPRESS
One of the earliest-approved heartworm preventives available, safe from 4 weeks of age and 2 pounds body weight, letting a puppy start protection well before the typical 6-to-8-week minimum of competing products.
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Heartgard Plus · 6-Week Standard
Heartgard Plus (Puppy Formula)
Safe for Puppies Over 6 Weeks · Rx Required · WORLD PET EXPRESS
Safe for puppies over 6 weeks old and also approved for pregnant dogs, a widely trusted option for a new puppy’s first heartworm preventive.
30
Revolution · Kitten & Puppy Formula
Revolution for Kittens & Puppies
Formulated for Under 5-Pound Young Animals · Rx Required · WORLD PET EXPRESS
Specifically sized and dosed for kittens and puppies under 5 pounds, protecting against heartworm and fleas at a life stage where standard adult formulas would be dosed incorrectly.
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Mosquito Protection
Since mosquitoes are the sole carriers of heartworm, reducing mosquito exposure around the home is a genuine complement to, though never a replacement for, monthly prevention.
🦙 Mosquito Protection Picks
31
Pet-Safe Mosquito Spray · ⭐ Top Pick
Pet-Safe Mosquito Repellent Spray
Reduces Bite Exposure Outdoors · OTC · AMAZON
A pet-safe repellent applied before outdoor time to reduce mosquito bites, a reasonable supplement to monthly prevention rather than a standalone substitute for it.
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Yard Mosquito Treatment
Outdoor Mosquito Yard Treatment
Reduces Mosquito Population Around the Home · OTC · AMAZON
Treats standing water and yard areas where mosquitoes breed, reducing overall mosquito pressure around a home where pets spend outdoor time.
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Outdoor Kennel Screening
Mosquito Netting for Outdoor Kennels
Physical Barrier for Outdoor Enclosures · OTC · AMAZON
A physical mesh barrier for an outdoor kennel or run, useful for pets who spend significant time outside during peak mosquito activity hours at dawn and dusk.
🎁 The Gift of Year-Round Protection
For the pet owner who already has heartworm prevention dialed in — or someone who doesn’t know where to start. These gift cards cover every category on this page.
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World Pet Express · ⭐ Pet Pharmacy Specialist
World Pet Express Gift Card
Prescription Heartworm Medications · WORLD PET EXPRESS
A certified pet pharmacy carrying the full range of prescription heartworm preventives on this page, often at meaningfully discounted prices compared to picking these up directly at a vet’s office.
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Chewy · Pet Specialist
Chewy Gift Card
Prescription Pharmacy · 24/7 Vet Chat · CHEWY
Chewy’s own pharmacy fills many of the prescriptions on this page directly, with free 24/7 chat access to a licensed vet team to help confirm the right product for your pet.
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Amazon · Mosquito Protection & Tools
Amazon Gift Card
Sprays · Yard Treatment · Outdoor Gear · AMAZON
Covers the mosquito protection sprays, yard treatments, and outdoor gear on this page, the most flexible option for the non-prescription side of a full prevention routine.
Best Heartworm Prevention — Buying Advice
8 Things to Check Before You Buy
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Never Skip the Pre-Test
A negative heartworm test is required before starting or restarting prevention in dogs 7 months or older. Giving prevention to an already-infected dog can trigger a dangerous reaction, and treating an active infection needs a completely different protocol.
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Take Cat Prevention Just as Seriously as Dog Prevention
There’s no approved treatment for heartworm in cats, only prevention. This makes consistent monthly dosing arguably more critical for cats than dogs, including indoor-only cats, since mosquitoes can still get inside.
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Screen Herding Breeds for MDR1 Sensitivity
Collies, Australian Shepherds, and related breeds can carry a gene mutation affecting how they process certain antiparasitic drugs. Discuss genetic screening and milbemycin-based alternatives with your vet.
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Understand That None of These Kill Adult Heartworms
Every product in this category only prevents larval stages from maturing. None of them treat an existing adult heartworm infection, which is why the pre-test matters so much.
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Ask About Generic Equivalents to Cut Cost
Tri-Heart Plus and other generics contain the same active ingredients as brand-name products at a meaningfully lower price. Buying 6- or 12-month supplies also typically costs less per dose than monthly purchases.
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Flag Liver Disease, Steroid Use, or Chemotherapy to Your Vet
Dogs with compromised liver function, on long-term steroids, or undergoing chemotherapy have specific product and timing considerations. Milbemycin-based options are often preferred in these situations, but always confirm with your vet.
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Consider an Injectable If Compliance Is a Real Risk
ProHeart 12 removes the missed-dose risk entirely with one annual injection. For a busy household or a dog that resists pills, this can mean genuinely better real-world protection than monthly dosing.
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Treat Mosquito Reduction as a Supplement, Not a Substitute
Repellents and yard treatments reduce mosquito exposure, but they don’t replace monthly prevention. Heartworm risk exists anywhere mosquitoes are active, including through open doors and windows.
Best Heartworm Prevention — FAQ
Best Heartworm Prevention — FAQ
Why do I need to test my dog before starting heartworm prevention?
Heartworm preventives are not treatments for an existing infection. Giving a preventive to a dog that already has heartworms can trigger a dangerous reaction, and an active infection requires an entirely different treatment protocol. A current negative test confirms prevention is actually appropriate to start.
Is heartworm prevention really necessary for indoor cats?
Yes. Mosquitoes can enter homes through doors, windows, and on clothing, and there’s no approved treatment for heartworm disease in cats once infected. Veterinarians strongly recommend year-round monthly prevention for all cats, including strictly indoor ones.
What is the MDR1 gene mutation, and does it affect my dog?
MDR1/ABCB1 is a gene mutation common in Collies, Australian Shepherds, and related herding breeds that affects how a dog processes certain antiparasitic drugs, including ivermectin at higher doses. A genetic test can confirm whether your dog carries it, and milbemycin-based products generally carry a higher safety margin for affected dogs.
What happens if I miss a monthly dose?
Missing even one dose can reduce protection and increase infection risk, since these products only work against the recent larval stage of heartworm. If a dose is missed, contact your vet about next steps, which may include retesting before resuming.
Is an injectable heartworm preventive better than a monthly pill?
For dogs where missed doses are a genuine risk, injectable options like ProHeart 12 can provide more reliable real-world protection since they remove the compliance problem entirely. Both formats are effective when used correctly; the right choice depends on your household’s routine and your vet’s recommendation.
How did NME select the products on this page?
Every item was evaluated against five criteria: clinical efficacy data, breed and health-condition-specific safety considerations, prescription status and accessibility, value relative to premium alternatives, and fit for the specific pet’s species, age, weight, and health history. Commission rates played no role in ranking or inclusion. This guide is educational and does not replace individualized veterinary advice.
Protect Your Pet With a Plan Your Vet Confirms
Every item on this page was selected based on clinical efficacy and safety data, not commission rate. Always confirm your pet’s current heartworm status and any product’s suitability with a veterinarian before starting.
