Best Heartworm Prevention

Pros

• DailyMed / NADA 141-521: prevents heartworm disease; treats/controls roundworms and hookworms; kills adult fleas; labeled for six tick species; prevents Borrelia burgdorferi by killing Ixodes scapularis; prevents Dipylidium caninum as a direct result of killing vector fleas.
• Zoetis pet-owner page: can be given with or without food. Dogs and puppies 8 weeks+, 2.8 lb+.
• One monthly chew can replace a separate heartworm preventive plus a separate flea/tick product when a veterinarian chooses this protocol.

Cons

• Contains sarolaner (isoxazoline). FDA fact sheet and the Trio label warn of neurologic adverse reactions including seizures, including in dogs without a prior history. Use with caution if there is a seizure/neurologic history.
• Prescription only. Not a cat product. Does not treat whipworms (unlike Interceptor Plus / Advantage Multi).
• Same product is also on our flea and tick ranking; this row scores the heartworm combo, not a second product.

Score breakdown

Specs

Actives

sarolaner, moxidectin, pyrantel pamoate

Agency

FDA NADA 141-521

Species

Dogs only (8 weeks+, 2.8 lb+)

Interval

Once monthly

Rx

Yes — veterinary prescription required

Score Notes

quality 9 = 3 HW + 2 RW/hook + 1 flea-tapeworm + 2 fleas + 1 ticks. safety 6 = 8 FDA −2 isoxazoline fact sheet. value 5 = 3 base + 2 flea combo. ease 8 = oral chew, with or without food.

Pros

• DailyMed / NADA 141-251 (dogs): prevents heartworm disease; treats circulating microfilariae; kills adult fleas; treats/controls hookworms, roundworms, whipworms, and sarcoptic mange. Puppies 7 weeks+, 3 lb+.
• Official Elanco consumer page also covers Advantage Multi for Cats (NADA 141-254): heartworm prevention, fleas, ear mites, roundworms, and hookworms; kittens 9 weeks+, 2 lb+; 5.1–9 lb cat size is labeled for ferrets ≥2 lb.
• Topical, so it is an option when a household cannot give a monthly chew. Elanco states heartworm prevention still holds if a dose is a few days late — treat immediately and resume the monthly schedule (label: apply monthly).

Cons

• Prescription only. Dog product must not be used on cats (2.5% moxidectin). Do not administer orally; dogs that lick the site can have serious reactions, worse in MDR1/avermectin-sensitive breeds. Children: 2 hours off the dog application site; 30 minutes for cats.
• Monthly topical residue vs a chew. Shampooing as often as weekly may reduce flea effectiveness. Not labeled for ticks.
• Pack shot on this row is the dog carton (20.1–55 lb SKU from the FDA label). Use only the species and weight tube on the box.

Score breakdown

Specs

Actives

imidacloprid + moxidectin

Agency

FDA NADA 141-251 (dogs); NADA 141-254 (cats)

Species

Dogs 7 weeks+, 3 lb+; official cat SKU 9 weeks+, 2 lb+; ferret on labeled cat size

Interval

Once monthly

Rx

Yes — veterinary prescription required

Score Notes

quality 8 = 3 HW + 2 RW/hook + 1 whip + 2 fleas. safety 7 = 8 FDA −1 dog-topical oral/cat warning. value 6 = 3 base + 2 flea combo + 1 extra worms. ease 6 = monthly topical.

Pros

• DailyMed / NADA 141-338: prevents heartworm disease; treats/controls adult roundworms, hookworms, whipworms, and tapeworms including Dipylidium caninum, Taenia pisiformis, Echinococcus multilocularis, and E. granulosus.
• Dogs and puppies 6 weeks+, 2 lb+. Elanco: offer by hand or with a small amount of food; 94% accepted from the hand in the cited field palatability study on the label.
• Not an isoxazoline and not an injectable — no FDA isoxazoline fact-sheet penalty and no ProHeart-style anaphylaxis warning on this chew.

Cons

• Prescription only. Does not kill fleas or ticks — households that need those still need a separate labeled product (Elanco itself pairs Interceptor Plus with Credelio or Seresto in vet materials).
• Label: fewer than 6 monthly doses after the last mosquito exposure may not provide complete heartworm prevention. Safety has not been evaluated in dogs used for breeding or in lactating females.
• Reported reactions for milbemycin oxime or praziquantel include vomiting, diarrhea, lethargy, ataxia, anorexia, convulsions, weakness, and salivation.

Score breakdown

Specs

Actives

milbemycin oxime, praziquantel

Agency

FDA NADA 141-338

Species

Dogs 6 weeks+, 2 lb+

Interval

Once monthly (continue at least 6 months after last mosquito exposure)

Rx

Yes — veterinary prescription required

Score Notes

quality 7 = 3 HW + 2 RW/hook + 1 whip + 1 tape. safety 8 = FDA start. value 4 = 3 base + 1 extra worms. ease 8 = oral chew.

Pros

• DailyMed / NADA 141-519: prevents heartworm disease for 12 months in healthy dogs 12 months of age and older; treats existing larval and adult hookworms (Ancylostoma caninum and Uncinaria stenocephala) at injection.
• Zoetis pet-owner page: the only FDA-approved product that prevents heartworm for a full year with one shot. Same visit as annual wellness is the compliance case.
• ProHeart 6 (NADA 141-189) remains the twice-yearly option for dogs 6 months+ but under 12 months — noted, not scored as a separate row this pass.

Cons

• Clinic-only injectable. Hypersensitivity / anaphylactic reactions can occur, including with vaccines, and can result in death. Do not give to sick, debilitated, underweight dogs or those previously hypersensitive. Veterinarians must be certified to administer it.
• Does not treat roundworms, whipworms, tapeworms, fleas, or ticks. Still need other labeled products for those parasites.
• Not for dogs under 12 months (use ProHeart 6 in that window). Owner cannot administer at home if the annual visit is missed.

Score breakdown

Specs

Actives

moxidectin extended-release injectable

Agency

FDA NADA 141-519 (ProHeart 6 is NADA 141-189)

Species

Healthy dogs 12 months+

Interval

Once every 12 months (clinic injection)

Rx

Yes — veterinary prescription and clinic administration required

Score Notes

quality 6 = 3 HW + 1 hookworm only + 2 twelve-month duration. safety 6 = 8 FDA −2 injectable hypersensitivity warning. value 5 = 3 base + 2 duration. ease 8 = once yearly vs monthly chews, clinic-only.

Pros

• DailyMed / NADA 140-971: prevents canine heartworm disease; treats/controls roundworms (T. canis, T. leonina) and three hookworm species (A. caninum, U. stenocephala, A. braziliense).
• Labeled for dogs 6 weeks of age and older with no minimum weight — the lowest age floor on this list. Offer by hand or in food; chews may be broken for dogs that swallow treats whole (choking/obstruction has been reported).
• Label safety: Heartgard products showed no signs of toxicity at 10× the recommended ivermectin dose in ivermectin-sensitive Collies when used as recommended. Also labeled for pregnant/breeding bitches, studs, and puppies ≥6 weeks.

Cons

• Prescription only. Does not treat whipworms, tapeworms, fleas, or ticks — narrower intestinal coverage than Interceptor Plus or Advantage Multi.
• Post-approval (2022) reported events include vomiting, diarrhea, lethargy, anorexia, seizures, ataxia, muscle tremors, hypersalivation, and pruritus. Not effective against adult heartworms; test before starting.
• If the interval between doses exceeds 30 days, ivermectin efficacy can be reduced. Give on or about the same day each month.

Score breakdown

Specs

Actives

ivermectin, pyrantel pamoate

Agency

FDA NADA 140-971

Species

Dogs 6 weeks+ (no minimum weight)

Interval

Once monthly

Rx

Yes — veterinary prescription required

Score Notes

quality 5 = 3 HW + 2 RW/hook. safety 8 = FDA start. value 3 = base only. ease 8 = oral chew.