20 Best Dog Heartworm Flea And Tick Prevention [2024]

Are you looking for the best Dog Heartworm Flea And Tick Prevention? Based on expert reviews, we ranked them. We've listed our top-ranked picks, including the top-selling Dog Heartworm Flea And Tick Prevention.

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# Preview Product
1 K9 Advantix II Flea and Tick Prevention for Large Dogs 4-Pack, 21-55 Pounds K9 Advantix II Flea and Tick Prevention for Large Dogs 4-Pack, 21-55 Pounds
2 TevraPet Activate II Flea and Tick Prevention for Large Dogs 21-55 pounds, 4 Monthly Doses of Fast... TevraPet Activate II Flea and Tick Prevention for Large Dogs 21-55 pounds, 4 Monthly Doses of...
3 K9 Advantix II Flea and Tick Prevention for Medium Dogs 4-Pack, 11-20 Pounds K9 Advantix II Flea and Tick Prevention for Medium Dogs 4-Pack, 11-20 Pounds
4 PetArmor Plus Flea and Tick Prevention for Dogs, Dog Flea and Tick Treatment, Waterproof Topical,... PetArmor Plus Flea and Tick Prevention for Dogs, Dog Flea and Tick Treatment, Waterproof Topical,...
5 PetArmor Plus Flea and Tick Prevention for Dogs, Dog Flea and Tick Treatment, Waterproof Topical,... PetArmor Plus Flea and Tick Prevention for Dogs, Dog Flea and Tick Treatment, Waterproof Topical,...
6 PetArmor Plus Flea and Tick Prevention for Dogs, Dog Flea and Tick Treatment, Waterproof Topical,... PetArmor Plus Flea and Tick Prevention for Dogs, Dog Flea and Tick Treatment, Waterproof Topical,...
7 TevraPet Activate II Flea and Tick Prevention for Extra Large Dogs over 55 pounds, 4 Monthly Doses... TevraPet Activate II Flea and Tick Prevention for Extra Large Dogs over 55 pounds, 4 Monthly...
8 TevraPet Activate II Flea and Tick Prevention for Dogs | 4 Count | Medium Dogs 11-20 lbs | Topical... TevraPet Activate II Flea and Tick Prevention for Dogs | 4 Count | Medium Dogs 11-20 lbs |...
9 TevraPet Activate II Flea and Tick Prevention for Dogs | 8 Months Supply | Medicine for Treatment... TevraPet Activate II Flea and Tick Prevention for Dogs | 8 Months Supply | Medicine for Treatment...
10 K9 Advantix II Flea and Tick Prevention for Small Dogs 4-Pack, 4-10 Pounds K9 Advantix II Flea and Tick Prevention for Small Dogs 4-Pack, 4-10 Pounds
11 TevraPet Activate II Flea and Tick Prevention for Small Dogs 4-10 pounds, 4 Monthly Doses of Fast... TevraPet Activate II Flea and Tick Prevention for Small Dogs 4-10 pounds, 4 Monthly Doses of Fast...
12 Fiproguard Flea & Tick Squeeze-On for Dogs Upto 22 lbs, 6-PACK Fiproguard Flea & Tick Squeeze-On for Dogs Upto 22 lbs, 6-PACK
13 ShieldTec Flea, Tick, and Mosquito Prevention for Dogs ShieldTec Flea, Tick, and Mosquito Prevention for Dogs
14 Advantage II 6-Dose Large Dog Flea Prevention, Topical Flea Treatment for Large Dogs 21-55 Pounds Advantage II 6-Dose Large Dog Flea Prevention, Topical Flea Treatment for Large Dogs 21-55 Pounds
15 PETARMOR Plus for Dogs Flea and Tick Prevention for Dogs, Long-Lasting & Fast-Acting Topical Dog... PETARMOR Plus for Dogs Flea and Tick Prevention for Dogs, Long-Lasting & Fast-Acting Topical Dog...
16 From Needles to Natural: Learning Holistic Pet Healing From Needles to Natural: Learning Holistic Pet Healing
17 Dogs Holistic Health Maintenance & Remedies Encyclopedia: Herbs, Vaccines, Food Nutrition, Healing... Dogs Holistic Health Maintenance & Remedies Encyclopedia: Herbs, Vaccines, Food Nutrition,...
18 K9 Advantix II Flea and Tick Prevention for Extra-Large Dogs 4-Pack, Over 55 Pounds K9 Advantix II Flea and Tick Prevention for Extra-Large Dogs 4-Pack, Over 55 Pounds
19 Frontline Plus Flea and Tick Treatment for Dogs (Large Dog, 45-88 Pounds, 3 Doses) Frontline Plus Flea and Tick Treatment for Dogs (Large Dog, 45-88 Pounds, 3 Doses)
20 Pet Honesty Flea & Tick Defense Supplement - Natural Flea and Tick Soft Chew for Dogs, Pest Defense... Pet Honesty Flea & Tick Defense Supplement - Natural Flea and Tick Soft Chew for Dogs, Pest...
Bestseller No. 1
K9 Advantix II Flea and Tick Prevention for Large Dogs 4-Pack, 21-55 Pounds
  • 4 monthly applications of K9 Advantix II flea and tick prevention for large dogs weighing 21-55 pounds
  • K9 Advantix II flea and tick prevention for dogs works through contact, so fleas, ticks and mosquitoes do not have to bite your dog to die
  • K9 Advantix II flea and tick control for dogs is an easy to apply topical formula
  • Starts working to kill fleas within 12 hours and keeps working for 30 days
  • Suitable for effective year-round dog flea and tick treatment for large dogs
SaleBestseller No. 2
TevraPet Activate II Flea and Tick Prevention for Large Dogs 21-55 pounds, 4 Monthly Doses of Fast...
  • Compare to K9 Advantix: Activate II uses Imidacloprid, Permethrin, and Pyriproxyfen - the same safe, fast acting and effective active ingredients used...
  • Vet approved for large dogs 21 to 55 pounds: Activate II topical flea drops were developed by veterinarians to repel and kill fleas and ticks on...
  • Break the Flea Lifecycle: Activate II stops and controls infestations by breaking the flea life cycle. Our flea treatment use an insect growth...
  • Waterproof and easy to use: Simply apply the topical drops to the base of your dog's neck, and the medicine will travel across the skin - remaining...
  • Made in America, satisfaction guaranteed: TevraPet Activate II is proudly made in the USA to the exacting standards we demand for our own pets. We are...
SaleBestseller No. 3
K9 Advantix II Flea and Tick Prevention for Medium Dogs 4-Pack, 11-20 Pounds
  • 4 monthly applications of K9 Advantix II flea and tick prevention for medium dogs weighing 11-20 pounds
  • K9 Advantix II flea and tick prevention for dogs works through contact, so fleas, ticks and mosquitoes do not have to bite your dog to die
  • K9 Advantix II flea and tick control for dogs is an easy to apply topical formula
  • Starts working to kill fleas within 12 hours and keeps working for 30 days
  • Suitable for effective year-round dog flea and tick treatment for medium dogs
SaleBestseller No. 4
PetArmor Plus Flea and Tick Prevention for Dogs, Dog Flea and Tick Treatment, Waterproof Topical,...
  • EFFECTIVE, WATERPROOF FLEA TREATMENT FOR DOGS: PetArmor Plus is a waterproof, flea & tick topical prevention for dogs that kills fleas, flea eggs,...
  • TRUSTED, VET QUALITY FORMULA: Containing fipronil and (S)-methoprene, the same active ingredients as FRONTLINE Plus for Dogs. PetArmor Plus for Dogs...
  • BREAK THE FLEA CYCLE: Unlike other flea and tick treatments that may temporarily suppress flea activity, PETARMOR Plus Dog Flea Treatment works by...
  • FAST ACTNG LONG-LASTING FLEA AND TICK PROTECTION: One application of PetArmor Plus lasts up to 30 days nose to tail. A 6-dose package lasts up to six...
  • EASY-TO-USE, LONG-LASTING: PetArmor Plus flea and tick treatment comes with three (3) waterproof topical applications that provides your pet flea...
SaleBestseller No. 5
PetArmor Plus Flea and Tick Prevention for Dogs, Dog Flea and Tick Treatment, Waterproof Topical,...
  • EFFECTIVE, WATERPROOF FLEA TREATMENT FOR DOGS: PetArmor Plus is a waterproof, flea & tick topical prevention for dogs that kills fleas, flea eggs,...
  • TRUSTED, VET QUALITY FORMULA: Containing fipronil and (S)-methoprene, the same active ingredients as FRONTLINE Plus for Dogs. PetArmor Plus for Dogs...
  • BREAK THE FLEA CYCLE: Unlike other flea and tick treatments that may temporarily suppress flea activity, PETARMOR Plus Dog Flea Treatment works by...
  • FAST ACTNG LONG-LASTING FLEA AND TICK PROTECTION: One application of PetArmor Plus lasts up to 30 days nose to tail. A 6-dose package lasts up to six...
  • EASY-TO-USE, LONG-LASTING: PetArmor Plus flea and tick treatment comes with three (3) waterproof topical applications that provides your pet flea...
SaleBestseller No. 6
PetArmor Plus Flea and Tick Prevention for Dogs, Dog Flea and Tick Treatment, Waterproof Topical,...
  • DOG FLEA AND TICK CONTROL: PetArmor Plus topical flea and tick prevention for medium dogs kills fleas, flea eggs, flea larvae, ticks, and chewing lice...
  • VET QUALITY FORMULA: This vet-quality formula flea treatment contains fipronil and begins killing fleas & ticks within 24 hours.
  • FAST-ACTING FLEA TREATMENT: PetArmor Plus is a fast-acting topical flea treatment for dogs that works by breaking the flea cycle, and killing flea...
  • FLEA AND TICK PREVENTION: PetArmor Plus for dogs helps you protect your furry family member from brown dog ticks, American dog ticks, lone star ticks,...
  • INCLUDES: Three (3) 0.045 fl. oz. waterproof topical applications for dog flea and tick control. For best results, apply flea & tick treatment for...
SaleBestseller No. 7
TevraPet Activate II Flea and Tick Prevention for Extra Large Dogs over 55 pounds, 4 Monthly Doses...
  • Compare to K9 Advantix: Activate II uses Imidacloprid, Permethrin, and Pyriproxyfen - the same safe, fast acting active ingredients used in Advantix...
  • Flea, tick, and mosquito protection: Activate II is approved by veterinarians to repel and kill fleas and ticks on contact - before your dog is...
  • Break the flea lifecycle FAST: Our topical drops stop and control infestations - our insect growth regulator (IGR) starts killing flea eggs and larvae...
  • Easy to apply, continuous prevention: Simply apply to the base of your dog's neck, and the waterproof solution will travel across the skin - providing...
  • Made in America, results guaranteed: TevraPet Activate II is made to the exacting standards we demand for our own pets. We're proud to help you...
SaleBestseller No. 8
TevraPet Activate II Flea and Tick Prevention for Dogs | 4 Count | Medium Dogs 11-20 lbs | Topical...
  • COMPARE TO K9 ADVANTIX II: Activate II uses Imidacloprid, Permethrin, and Pyriproxyfen - the same safe, fast acting active ingredients used in...
  • ACTIVELY PROTECTS YOUR DOG: Activate II is approved by veterinarians to repel and kill fleas and ticks on contact - before your dog is exposed to...
  • STOP INFESTATIONS FAST: Our topical drops prevent infestations by breaking the flea life cycle - our insect growth regulator (IGR) starts killing flea...
  • EASY TO APPLY: Simply apply to the base of your dog's neck, and the waterproof solution will travel across the skin - providing continuous protection...
  • MADE IN AMERICA - RESULTS GUARANTEED: TevraPet Activate II is made to the quality standard we demand for our own pets. We're proud to help you protect...
Bestseller No. 9
TevraPet Activate II Flea and Tick Prevention for Dogs | 8 Months Supply | Medicine for Treatment...
  • Vet quality - Contains imidacloprid, permethrin and pyriproxyfen, the active ingredients found in the Leading Brand and trusted by vets everywhere
  • Repels - proven to repel fleas, flea eggs, ticks, biting flies and mosquitoes. Does not require biting!
  • Effective and Powerful - This broad spectrum flea and tick topical kills all stages of fleas, flea eggs, ticks, and lice - and mosquitoes
  • Easy-to-apply - eight month supply, use monthly on your dog. No need to reapply after swimming or bathing
  • American made - proudly made in the USA
Bestseller No. 10
K9 Advantix II Flea and Tick Prevention for Small Dogs 4-Pack, 4-10 Pounds
  • 4 monthly applications of K9 Advantix II flea and tick prevention for small dogs weighing 4-10 pounds
  • K9 Advantix II flea and tick prevention for dogs works through contact, so fleas, ticks and mosquitoes do not have to bite your dog to die
  • K9 Advantix II flea and tick control for dogs is an easy to apply topical formula
  • Starts working to kill fleas within 12 hours and keeps working for 30 days
  • Suitable for effective year-round dog flea and tick treatment for small dogs
SaleBestseller No. 11
TevraPet Activate II Flea and Tick Prevention for Small Dogs 4-10 pounds, 4 Monthly Doses of Fast...
  • Compare to K9 Advantix: Activate II uses Imidacloprid, Permethrin, and Pyriproxyfen - the same safe, fast acting and effective active ingredients used...
  • Vet approved for small dogs 4 to 10 pounds: Activate II topical flea drops were developed by veterinarians to repel and kill fleas and ticks on...
  • Break the Flea Lifecycle: Activate II stops and controls infestations by breaking the flea life cycle. Our flea treatment use an insect growth...
  • Waterproof and easy to use: Simply apply the topical drops to the base of your dog's neck, and the medicine will travel across the skin - remaining...
  • Made in America, satisfaction guaranteed: TevraPet Activate II is proudly made in the USA to the exacting standards we demand for our own pets. We are...
Bestseller No. 12
Fiproguard Flea & Tick Squeeze-On for Dogs Upto 22 lbs, 6-PACK
  • DOG FLEA AND TICK CONTROL: SENTRY Fiproguard topical flea and tick prevention for dogs kills fleas, ticks and chewing lice for up to 30 days.
  • VET QUALITY FORMULA: SENTRY Fiproguard is a vet-quality formula flea treatment that contains fipronil.
  • SMALL DOGS: Flea and tick control for use on dogs and puppies over 8 weeks of age, weighing 5-22 pounds; can be used on breeding, pregnant, and...
  • TICK PREVENTION: Fiproguard for dogs also kills brown dog ticks, American dog ticks, lone star ticks and deer ticks (which may transmit Lyme disease).
  • INCLUDES: Six (6) 0.023 fl. oz. applicators, a six month supply of waterproof topical applications for dog flea and tick control. For best results,...
Bestseller No. 13
ShieldTec Flea, Tick, and Mosquito Prevention for Dogs
  • 4X PROTECTION FOR ACTIVE DOGS: Topical formula destroys fleas, flea eggs, ticks, lice, and even mosquitos on contact
  • POWERFUL, LONG-LASTING PREVENTION: Prevent mosquito or tick bites and lice or flea infestations with a single application per month
  • THE OUTDOORSMAN’S CHOICE: Waterproof treatment drops offer protection through the harshest conditions of wind, sun, or even heavy rain
  • NON-IRRITATING AND SAFE FOR PUPPIES: Manufactured in the USA to meet strict EPA guidelines for pet exposure, even in small dogs
Bestseller No. 14
Advantage II 6-Dose Large Dog Flea Prevention, Topical Flea Treatment for Large Dogs 21-55 Pounds
  • 6-dose large dog flea prevention, topical flea treatment for large dogs weighing 21-55 pounds
  • Easy-to-apply and pre-measured application tubes, fragrance-free and designed specifically to treat and prevent fleas on dogs
  • Advantage II large dog flea treatment kills fleas through contact, meaning fleas don’t have to bite your dog in order to die
  • Starts working within 12 hours and protects your dog for up to 30 days
  • Vet-recommended, fragrance-free and designed specifically to treat and prevent fleas and lice on dogs
Bestseller No. 15
PETARMOR Plus for Dogs Flea and Tick Prevention for Dogs, Long-Lasting & Fast-Acting Topical Dog...
  • EFFECTIVE, WATERPROOF FLEA TREATMENT FOR DOGS: PetArmor Plus is a waterproof, flea and tick topical prevention for dogs that kills fleas, flea eggs,...
  • TRUSTED, VET QUALITY FORMULA: Containing fipronil and (S)-methoprene, the same active ingredients as FRONTLINE Plus for Dogs. PetArmor Plus for Dogs...
  • BREAK THE FLEA CYCLE: Unlike other flea and tick treatments that may temporarily suppress flea activity, PETARMOR Plus Dog Flea Treatment works by...
  • FAST ACTNG LONG-LASTING FLEA AND TICK PROTECTION: One application of PetArmor Plus lasts up to 30 days nose to tail. A 6-dose package lasts up to six...
  • EASY-TO-USE, LONG-LASTING: PetArmor Plus flea and tick treatment comes with three (3) waterproof topical applications that provides your pet flea...
Bestseller No. 16
From Needles to Natural: Learning Holistic Pet Healing
  • Amazon Kindle Edition
  • Morgan D.V.M., Judy (Author)
  • English (Publication Language)
  • 302 Pages - 07/21/2014 (Publication Date) - Archway Publishing (Publisher)
Bestseller No. 17
Dogs Holistic Health Maintenance & Remedies Encyclopedia: Herbs, Vaccines, Food Nutrition, Healing...
  • Lopez, Mercy (Author)
  • English (Publication Language)
  • 444 Pages - 04/24/2020 (Publication Date) - Everything Dogs By Mercy Lopez (Publisher)
SaleBestseller No. 18
K9 Advantix II Flea and Tick Prevention for Extra-Large Dogs 4-Pack, Over 55 Pounds
  • FOUR MONTHS PROTECTION: 4 monthly applications of K9 Advantix II flea and tick prevention for extra-large dogs weighing 55 pounds or more
  • FLEA, TICK AND MOSQUITO PROTECTION: K9 Advantix II flea and tick prevention for dogs works through contact, so fleas, ticks and mosquitoes do not have...
  • EASY TO APPLY: K9 Advantix II flea and tick control for dogs is an easy to apply topical formula
  • STARTS WORKING WITHIN 12 HOURS: Starts working to kill fleas within 12 hours and keeps working for 30 days
  • EFFECTIVE YEAR-ROUND: Suitable for effective year-round flea and tick treatment for extra-large dogs
SaleBestseller No. 19
Frontline Plus Flea and Tick Treatment for Dogs (Large Dog, 45-88 Pounds, 3 Doses)
  • Waterproof flea and tick treatment for dogs: Frontline Plus for Dogs provides waterproof, fast-acting, long-lasting flea and tick treatment and...
  • Break the flea life cycle with Frontline: Frontline flea and tick treatment for dogs kills adult fleas plus flea eggs and larvae to stop existing...
  • Kills fleas and ticks: Frontline flea and tick treatment for dogs kills fleas, flea eggs, lice, and ticks. This flea and tick treatment kills ticks,...
  • Trusted flea and tick protection for dogs: Frontline has been trusted by veterinarians for nearly 20 years. Made with 2 tough killing ingredients,...
  • Lasting flea and tick protection: Frontline's long-lasting formula is stored in the oil glands of the pet’s skin to give non-stop flea and tick...
Bestseller No. 20
Pet Honesty Flea & Tick Defense Supplement - Natural Flea and Tick Soft Chew for Dogs, Pest Defense...
  • A Natural Flea + Tick Defense - These delicious hickory bacon flavored soft chews promote the body's natural response to ward off fleas, ticks and...
  • Builds Daily + Long-Term Resistance When Given Every Day - 100% safe levels of natural ingredients like coconut oil, garlic, B vitamins and omegas...
  • Easier + Less Mess Than Oils, Sprays and Collars - These soft chews have a delicious hickory bacon flavor that your dog will love.1-3 treats a day...
  • Made with Active Ingredients + NO Toxins, Soy, or GMOs - PetHonesty products are not only made with safe natural ingredients but they contain no harsh...
  • GMP Certified Facility | NASC Member Company - All PetHonesty products are made in the US with US and globally sourced ingredients and are produced in...

Having trouble finding a great Dog Heartworm Flea And Tick Prevention?

This problem is well understood by us because we have gone through the entire Dog Heartworm Flea And Tick Prevention research process ourselves, which is why we have put together a comprehensive list of the best Dog Heartworm Flea And Tick Preventions available in the market today.

After hours of searching and using all the models on the market, we have found the best Dog Heartworm Flea And Tick Prevention for 2023. See our ranking below!

How Do You Buy The Best Dog Heartworm Flea And Tick Prevention?

Do you get stressed out thinking about shopping for a great Dog Heartworm Flea And Tick Prevention? Do doubts keep creeping into your mind?

We understand, because we’ve already gone through the whole process of researching Dog Heartworm Flea And Tick Prevention, which is why we have assembled a comprehensive list of the greatest Dog Heartworm Flea And Tick Prevention available in the current market. We’ve also come up with a list of questions that you probably have yourself.

John Harvards has done the best we can with our thoughts and recommendations, but it’s still crucial that you do thorough research on your own for Dog Heartworm Flea And Tick Prevention that you consider buying. Your questions might include the following:

  • Is it worth buying an Dog Heartworm Flea And Tick Prevention?
  • What benefits are there with buying an Dog Heartworm Flea And Tick Prevention?
  • What factors deserve consideration when shopping for an effective Dog Heartworm Flea And Tick Prevention?
  • Why is it crucial to invest in any Dog Heartworm Flea And Tick Prevention, much less the best one?
  • Which Dog Heartworm Flea And Tick Prevention are good in the current market?
  • Where can you find information like this about Dog Heartworm Flea And Tick Prevention?

We’re convinced that you likely have far more questions than just these regarding Dog Heartworm Flea And Tick Prevention, and the only real way to satisfy your need for knowledge is to get information from as many reputable online sources as you possibly can.

Potential sources can include buying guides for Dog Heartworm Flea And Tick Prevention, rating websites, word-of-mouth testimonials, online forums, and product reviews. Thorough and mindful research is crucial to making sure you get your hands on the best-possible Dog Heartworm Flea And Tick Prevention. Make sure that you are only using trustworthy and credible websites and sources.

John Harvards provides an Dog Heartworm Flea And Tick Prevention buying guide, and the information is totally objective and authentic. We employ both AI and big data in proofreading the collected information.

How did we create this buying guide? We did it using a custom-created selection of algorithms that lets us manifest a top-10 list of the best available Dog Heartworm Flea And Tick Prevention currently available on the market.

This technology we use to assemble our list depends on a variety of factors, including but not limited to the following:

  1. Brand Value: Every brand of Dog Heartworm Flea And Tick Prevention has a value all its own. Most brands offer some sort of unique selling proposition that’s supposed to bring something different to the table than their competitors.
  2. Features: What bells and whistles matter for an Dog Heartworm Flea And Tick Prevention?
  3. Specifications: How powerful they are can be measured.
  4. Product Value: This simply is how much bang for the buck you get from your Dog Heartworm Flea And Tick Prevention.
  5. Customer Ratings: Number ratings grade Dog Heartworm Flea And Tick Prevention objectively.
  6. Customer Reviews: Closely related to ratings, these paragraphs give you first-hand and detailed information from real-world users about their Dog Heartworm Flea And Tick Prevention.
  7. Product Quality: You don’t always get what you pay for with an Dog Heartworm Flea And Tick Prevention, sometimes less, and sometimes more.
  8. Product Reliability: How sturdy and durable an Dog Heartworm Flea And Tick Prevention is should be an indication of how long it will work out for you.

John Harvards always remembers that maintaining Dog Heartworm Flea And Tick Prevention information to stay current is a top priority, which is why we are constantly updating our websites. Learn more about us using online sources.

If you think that anything we present here regarding Dog Heartworm Flea And Tick Prevention is irrelevant, incorrect, misleading, or erroneous, then please let us know promptly!

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FAQ:

Q: Which heartworm medicine is best?

A: The most common types of heartworm prevention medications include ivermectin (Heartgard), milbemycin (Interceptor), and selamectin (Revolution). Each of these drugs and the variations of them available will kill heartworm, and some of them will also kill roundworm, hookworm, tapeworms, whipworms, and even fleas.

Q: Does Heartgard Plus kill fleas?

A: Heartgard Plus and Interceptor do not prevent fleas and ticks. If you need flea and tick prevention, you’ll need another medication. They do work to kill and prevent heartworm and other parasitic worms. Interceptor Spectrum comes in four dosages.

Q: When to start heartworm medication?

A: You should start a puppy on heartworm prevention (i.e., heartworm medicine) as soon as possible. The American Heartworm Society recommends starting a puppy on heartworm prevention no later than eight weeks of age. Each heartworm prevention product will have different ages and weights in which it is safe to start a puppy on heartworm prevention.

Q: What are the options for heartworm prevention for dogs?

A: As it turns out, low-dose ivermectin therapy in dogs with no sensitivity to the drug, in combination with the antibiotic doxycycline, can be an extremely effective, inexpensive option for treating heartworm infection.