NexGard Plus for Dogs: What It Treats, How It Works, and Dosing Guide
NexGard Plus combines three parasite-fighting ingredients into a single monthly beef-flavored chew. It covers fleas, ticks, heartworm, roundworms, hookworms, and tapeworms – the full slate of common parasites dogs face. Understanding how each component works and what the product does and does not cover helps owners use it correctly.
What Is NexGard Plus?
NexGard Plus is a prescription oral chewable tablet for dogs that combines three active pharmaceutical ingredients into a single monthly dose. It was developed by Boehringer Ingelheim as an expanded version of the original NexGard (afoxolaner only), adding milbemycin oxime and praziquantel to broaden its parasite coverage significantly.
The result is a product that replaces what would otherwise require separate heartworm prevention, flea and tick treatment, and deworming products – simplifying parasite management for owners and improving compliance by reducing the number of medications a dog needs to receive each month.
NexGard Plus is approved for dogs and puppies 8 weeks of age and older weighing at least 1.8 kg (approximately 4 lb). It requires a veterinary prescription in most regions.
The Three Active Ingredients
Afoxolaner blocks GABA-gated chloride channels in insect and arachnid nervous systems, causing uncontrolled neuronal excitation and death. It has selective toxicity – these channels differ between invertebrates and mammals, making it highly toxic to parasites at doses well below those causing mammalian effects. Starts killing fleas within 4 hours; kills over 99% within 24 hours. Kills multiple tick species including black-legged, American dog, brown dog, and lone star ticks.
Milbemycin oxime enhances glutamate-gated chloride ion channel activity in nematodes (roundworms) and arthropods, causing flaccid paralysis and death. It eliminates circulating Dirofilaria immitis larvae (L3 and L4 stages) before they can mature into adult heartworms, providing monthly heartworm prevention. It also treats and controls intestinal roundworms (Toxocara canis, Toxascaris leonina), hookworms (Ancylostoma caninum, Ancylostoma braziliense, Uncinaria stenocephala), and whipworms (Trichuris vulpis).
Praziquantel increases permeability of tapeworm cell membranes to calcium, causing intense muscular contraction, paralysis, and disintegration of the worm. It is effective against Dipylidium caninum (the flea tapeworm, the most common species in dogs) and Taenia species. Because praziquantel treats the existing tapeworm infection at the time of dosing but does not prevent re-infection, dogs that continue to ingest fleas (the intermediate host for Dipylidium) may become reinfected between monthly doses.
Full Parasite Coverage at a Glance
| Parasite | NexGard Plus | Active Ingredient | Notes |
|---|---|---|---|
| Fleas (all life stages via kill) | ✓ Yes | Afoxolaner | Kills adults; breaks cycle by preventing egg-laying |
| Ticks (multiple species) | ✓ Yes | Afoxolaner | Must attach to receive lethal dose; some tick-borne disease transmission still possible |
| Heartworm prevention | ✓ Yes | Milbemycin oxime | Prevents; does not treat existing adult infection |
| Roundworms | ✓ Yes | Milbemycin oxime | Treats and controls T. canis and T. leonina |
| Hookworms | ✓ Yes | Milbemycin oxime | Treats multiple Ancylostoma and Uncinaria species |
| Whipworms | ✓ Yes | Milbemycin oxime | Treats Trichuris vulpis |
| Tapeworms | ✓ Yes | Praziquantel | Treats Dipylidium caninum and Taenia spp. |
| Sarcoptic mange (scabies) | ✗ No | – | Not labeled; afoxolaner has activity but not approved indication |
| Demodex mites | ✗ No | – | Not an approved indication for NexGard Plus |
| Fleas (environmental reservoir) | ✗ No | – | Does not treat environment; home treatment needed during infestation |
Dosing by Weight
NexGard Plus is given once monthly. It comes in five chew sizes to cover the full range of dog weights. Each size contains a fixed dose of all three active ingredients scaled to the weight range.
| Chew Size | Dog Weight Range | Afoxolaner | Milbemycin | Praziquantel |
|---|---|---|---|---|
| XS | 1.8 – 3.6 kg (4 – 8 lb) | 11.25 mg | 2.25 mg | 56.25 mg |
| Small | 3.6 – 7.5 kg (8 – 17 lb) | 28.3 mg | 5.65 mg | 141.5 mg |
| Medium | 7.5 – 15 kg (17 – 33 lb) | 68 mg | 13.5 mg | 340 mg |
| Large | 15 – 30 kg (33 – 66 lb) | 136 mg | 27 mg | 680 mg |
| XL | 30 – 60 kg (66 – 132 lb) | 272 mg | 54 mg | 1360 mg |
For dogs over 60 kg, the appropriate combination of chews should be used. The product should be given on the same day each month. If a dose is missed, give it as soon as possible and resume the monthly schedule.
Dogs should be tested for heartworm infection before starting NexGard Plus or any heartworm preventative. Giving a macrocyclic lactone like milbemycin oxime to a dog with an existing adult heartworm infection does not treat the infection and can, in microfilaremic dogs (those with circulating larvae), cause a severe reaction from mass die-off of microfilariae. A negative heartworm test confirms it is safe to begin prevention.
Safety Profile and Precautions
Neurological Precaution (Isoxazoline Class)
The FDA has issued a class-wide advisory for isoxazoline-class ectoparasiticides (which includes afoxolaner) noting that neurological adverse events – including muscle tremors, ataxia, and seizures – have been reported in some dogs and cats treated with these products. Most affected animals have pre-existing neurological conditions that lower the seizure threshold.
For the vast majority of healthy dogs, NexGard Plus is well tolerated with only mild and transient side effects. However, owners of dogs with known seizure disorders or neurological conditions should discuss this with their vet before starting the product.
Common Side Effects
- Vomiting: Most commonly reported side effect, usually mild and self-limiting
- Diarrhea: Occasional loose stools after administration
- Lethargy: Mild and transient in some dogs
- Decreased appetite: Usually resolves within 24 hours
- Pruritus (itching): Occasionally reported
Dogs with the MDR1 (ABCB1) gene mutation – most commonly Collies, Australian Shepherds, Shelties, and related herding breeds – can have increased sensitivity to macrocyclic lactones including milbemycin oxime. At the doses used in NexGard Plus for heartworm prevention (which are significantly lower than the doses used for demodex or other conditions), the risk is considered low. However, genetic testing for the MDR1 mutation is available and recommended before starting macrocyclic lactone-containing products in high-risk breeds, particularly at higher doses.
NexGard Plus vs. Simparica Trio vs. Interceptor Plus
Several combination parasite products are now available that aim to consolidate monthly parasite management into a single chew. The main alternatives to NexGard Plus are:
- Simparica Trio (Zoetis): Contains sarolaner (isoxazoline), moxidectin (macrocyclic lactone), and pyrantel. Covers fleas, ticks, heartworm, roundworms, hookworms, and whipworms. Does not contain a tapeworm agent. Available for dogs 2.5+ kg, 8 weeks and older.
- Interceptor Plus (Elanco): Contains milbemycin oxime and praziquantel. Covers heartworm, roundworms, hookworms, whipworms, and tapeworms but does NOT treat fleas or ticks. A separate flea/tick product is needed alongside it.
- Trifexis (Elanco): Contains spinosad and milbemycin oxime. Covers fleas, heartworm, and some intestinal worms but does not treat ticks or tapeworms.
NexGard Plus is currently one of the only single-chew products that includes coverage for tapeworms (via praziquantel) in addition to flea, tick, heartworm, and intestinal worm coverage. For dogs in environments where flea tapeworm exposure is common, this can be a meaningful advantage over products that require a separate tapeworm treatment.
When to Give NexGard Plus and Year-Round Use
NexGard Plus is designed for year-round monthly administration. Even in climates with cold winters, year-round heartworm prevention is recommended by the American Heartworm Society because:
- Heartworm-transmitting mosquitoes can be present in warmer microenvironments even during mild winters
- Consistent monthly dosing prevents the risk of missing the start of parasite season
- Year-round deworming with milbemycin oxime helps reduce the environmental reservoir of roundworms and hookworms, which is a public health benefit (both can infect humans)
- Tapeworm re-exposure through flea ingestion occurs year-round for indoor/outdoor dogs in flea-endemic regions
Frequently Asked Questions
One Chew, Six Parasites
Parasite prevention compliance goes up when the regimen is simple. NexGard Plus reduces five or more separate monthly products down to one. For owners managing heartworm risk, flea and tick exposure, and intestinal parasite control simultaneously, consolidating into a single monthly chew lowers the chance that one protection gets forgotten – which is when parasites find their opening.