Are you confused about heartworm prevention options? These two charts compare current heartworm preventive products side by side to assist you in determining which is right for your situation.
In the second chart, LD50 stands for lethal dose to 50 percent of a population. Typically lethal doses are expressed as oral (toxin taken by mouth) or dermal (toxin placed on the skin). LD50s are usually determined with lab animal species such as rats, mice, and rabbits, but occasionally information is available for dogs. LD50s are expressed in milligrams of ingredients per kilogram of animal body weight (i.e. mg/kg) and provide a way to compare the toxicity of different substances.
The higher the LD50, the less toxic a substance is. Some of the materials reviewed here are so safe that LD50 has not been determined and we can only say that it is greater than a certain amount tested. The highest numbers represent the safest numbers.
Not all products listed here are available in every country. Always check with your veterinarian about the best options for your pet.
 
|  | ForDogs or Cats
 | Heartworm Preventing Ingredient | Other Ingredients for Control of Other Parasites | Other Parasites Controlled | Mode of Application | Youngest Age to Start Using | 
| Heartgardfor Dogs
 | Dogs | Ivermectin | None | None | oral | 6 weeks | 
| Heartgard Plus,Iverhart Plus,
 Iverhart Max,
 Triheart Plus,
 Pet Trust Plus
 | Dogs | Ivermectin | PyrantelPamoate
 Iverhart Max also
 has praziquantel
 | hookworms, roundwormsIverhart Max also covers tapeworms
 | oral | 6 weeks | 
| Heartgardfor Cats
 | Cats | Ivermectin | None | hookworms | oral | 6 weeks | 
| Interceptor,MilbeGuard,
 Milbehart
 | Dogsand Cats
 | Milbemycin Oxime | None | hookworms, roundworms, whipworms
 
 | oral | 4 weeksfor puppies
 6 weeks
 for kittens
 | 
| Interceptor Plus | Dogs | Milbemycin Oxime | Praziquantel | hookworms, roundworms, whipworms, tapeworms | oral | 6 weeks (and at least 2 lbs) | 
| Sentinel,Sentinel Spectrum
 | Dogs | Milbemycin Oxime | LufenuronSentinel Spectrum also has praziquantel
 | hookworms, roundworms, whipworms, sterilizes fleasSentinel Spectrum also covers tapeworms
 | oral | 6 weeks (and at least 2 lbs) | 
| Revolution,Paradyne, Revolt
 | Dogsand Cats
 | Selamectin | None | For dogs: fleas, ticks, ear mites, sarcoptic mange mitesFor cats:  fleas, ear mites, hookworms, roundworms
 | topical | 6 weeksfor puppies
 8 weeks
 for kittens
 | 
| Advantage Multi,Imoxi Topical
 | Dogsand Cats
 | Moxidectin | Imidacloprid | For dogs: fleas, hookworms, roundworms, whipwormsFor cats: fleas, ear mites, hookworms, roundworms
 | topical | 7 weeksfor puppies
 9 weeks
 for kittens
 | 
| Proheart 6,Proheart 12
 | Dogs | Moxidectin | None | hookworms | injectable | 6 months for Proheart 6, 12 months for Proheart 12 | 
| Trifexis | Dogs | Milbemycin Oxime | Spinosad | fleas, hookworms, roundworms, whipworms | oral | 8 weeks | 
| Coraxis | Dogs | Moxidectin | None | roundworms, hookworms, whipworms | topical | 7 weeks (and at least 3 lbs) | 
| Simparica Trio | Dogs | Moxidectin | Sarolaner, pyrantel pamoate | fleas, ticks, roundworms, hookworms | oral | 8 weeks (and at least 2.8 lbs) | 
| Bravecto Plus | Cats | Moxidectin | Fluralaner (for fleas and ticks) | ticks, fleas, hookworms, roundworms | topical | 6 months | 
| NexGard Spectra | Dogs | Milbemycin Oxime | Afoxolaner | flea, tick, mites, heartworm, hookworm, roundworm, whipworms, flea tapeworms
 | oral | 8 weeks (and at least 4.4lbs) | 
    
|  | How Often Used | Approved for Pregnancy and Lactation? | Water-proof? | Safe to Give to Heartworm-Positive Animals? | Manufacturer Website | LD50 | 
| Heartgard for Dogs | Monthly | yes | yes | yes | Heartgard | 10 mg/kg in rats orally according to the MSDS sheet for Parade Equine Gel | 
| Heartgard Plus,Iverhart Plus,
 Iverhart Max,
 Triheart Plus,
 Pet Trust Plus
 | monthly | yes | yes | yes | Heartgard PlusIverhart Plus
 Iverhart Max
 Triheart Plus
 PetTrustPlus
 
 | 10 mg/kg in rats orally for ivermectin; >690 mg/kg in dogs orally for Pyrantel Pamoate according to The Elephant Formulary by Mikota and Plumb
 | 
| Heartgard for Cats |  Discontinued by manufacturer | 
| Interceptor,MilbeGuard,
 Milbehart
 | monthly | yes | yes | In most cases yes, but if microfilariae numbers are high then no | Interceptor MilbeGuard
 | LD50 information unavailable
 Symptoms of tremors and incoordination result at 19 times the recommended dose
 | 
| Interceptor Plus | monthly | not tested for lactation, consult your vet regarding use in pregnancies | yes | In most cases yes, but if microfilariae numbers are high then no | Interceptor Plus | LD50 information unavailable
 Symptoms of tremors and incoordination result at 19 times the recommended dose
 | 
| Sentinel, Sentinel Spectrum | monthly | yes | yes | In most cases yes, but if microfilariae numbers are high then no | Sentinel | LD50 information unavailable
 Symptoms of tremors and incoordination result at 19 times recommended dose
 | 
| Revolution,Paradyne, Revolt
 | monthly | yes | yes | yes | Revolution | >1600 mg/kg in the rat orally | 
| Advantage Multi,Imoxi Topical
 | monthly | no | no | yes | AdvantageMulti
 | Moxidectin: 106 mg/kg orally;Imidacloprid: 450 mg/kg in the rat orally
 | 
| Proheart 6,Proheart 12
 | every 6 months for Proheart 6, every 12 months for Proheart 12
 | yes | yes | No, in fact, owners must agree to pre-treatment labwork including heartworm testing | Proheart 6 | 263 mg/kg in the rat when given by injection (the dose used therapeutically is 0.17mg/kg) | 
| Trifexis | monthly | The manufacturer cautions use, says to discuss with your veterinarian | yes | In most cases, yes but if microfilariae numbers are high then no | Trifexis | Milbemycin Oxime: LD50 information unavailable Spinosad: >3,000 mg/kg in rats; >2,000 mg/kg in rabbits (translates to over 30 times recommended dose)
 | 
| Coraxis | monthly | no | no | yes | BayerDVM | 106 mg/kg orally | 
| Simparica Trio | monthly | no | yes | no | Zoetis | 783 mg/kg for rats orally | 
| Bravecto Plus | every 2 months | no | no | The manufacturer recommends use with caution | Merck | Fluralaner: Dermal LD50: >2000mg/kg (rat) Moxidectin: 106 mg/kg orally
 | 
| NexGard Spectra | monthly | not tested for pregnancy or lactation, consult your vet regarding use in pregnancies | yes | Not evaluated by the manufacturer | NexGard Spectra | Afoxolaner: up to 1,000mg/kg orally in ratsMilbemycin oxime: range of 532mg/kg-946mg/kg, varied in mice and rats.
 |