NexGard Plus Chewables for Dogs: Complete Prescription Drug Guide
Complete guide to NexGard Plus chewables for dogs: dosage, side effects, drug interactions, cost, and veterinary guidance for heartworm and parasite prevention.
⚠️ PRESCRIPTION-ONLY NOTICE: NexGard Plus is a prescription veterinary medication that requires a valid veterinarian-client-patient relationship (VCPR). This medication must only be used under direct veterinary supervision. Never administer this or any prescription parasiticide without your veterinarian's explicit guidance and current prescription.
If you've been searching for comprehensive parasite protection for your dog, you've likely encountered NexGard Plus chewables. This prescription medication combines three active ingredients to deliver broad-spectrum coverage against fleas, ticks, heartworms, and intestinal parasites — all in a single monthly beef-flavored chew. But before you request a prescription, you need to understand exactly how it works, what it costs, and whether it's the right fit for your dog's health profile.
This guide breaks down everything you need to discuss with your veterinarian about NexGard Plus chewables for dogs, from mechanism of action to real-world dosing considerations.
What Is NexGard Plus and What Is It Used For?
NexGard Plus is a veterinary prescription-only, soft chewable tablet manufactured by Boehringer Ingelheim. It received FDA approval for use in dogs and puppies aged 8 weeks and older, weighing at least 4.4 lb (2 kg). Unlike the original NexGard (which contains only afoxolaner for flea and tick control), NexGard Plus adds two additional active ingredients to expand parasite coverage.
FDA-approved veterinary uses include:
- Flea treatment and prevention — kills adult fleas (Ctenocephalides felis) and prevents flea egg laying
- Tick treatment and control — effective against the Lone Star tick, American dog tick, black-legged (deer) tick, and brown dog tick
- Heartworm disease prevention — prevents Dirofilaria immitis infection
- Intestinal parasite treatment and control — treats and controls roundworms (Toxocara canis) and hookworms (Ancylostoma caninum, Uncinaria stenocephala)
- Tapeworm treatment — effective against Dipylidium caninum, Taenia pisiformis, and Echinococcus multilocularis
Common off-label uses (prescribed at veterinarian discretion) may include management of sarcoptic mange (Sarcoptes scabiei) and demodectic mange (Demodex canis), as the afoxolaner component has demonstrated efficacy against these mites in clinical settings. Your veterinarian will determine if off-label use is appropriate for your dog's specific condition.
How Does NexGard Plus Work? Drug Class and Mechanism
Three Active Ingredients, Three Attack Vectors
NexGard Plus combines three pharmacologically distinct compounds, each targeting a different class of parasite:
1. Afoxolaner (Isoxazoline class) — 68 mg per standard chew
Afoxolaner is a systemic insecticide and acaricide. After your dog ingests the chew, afoxolaner is absorbed into the bloodstream. When fleas or ticks bite your dog and ingest blood containing afoxolaner, it binds to chloride channels (specifically GABA-gated and glutamate-gated channels) in the parasite's nervous system. This causes uncontrolled neuronal excitation, leading to paralysis and death of the parasite. Because afoxolaner works systemically, parasites must bite to be killed — they won't simply die on contact with your dog's fur.
2. Moxidectin (Macrocyclic lactone class) — 2.3 mg per standard chew
Moxidectin targets heartworm larvae (L3 and L4 stages) and certain intestinal nematodes. It works by binding to glutamate-gated chloride channels in the parasite's neuromuscular junctions, causing flaccid paralysis. The heartworm larvae are killed before they can mature into adults and migrate to the heart and pulmonary arteries. Moxidectin also disrupts the neuromuscular function of roundworms and hookworms, leading to their expulsion.
3. Praziquantel (Anthelmintic class) — 68 mg per standard chew
Praziquantel specifically targets cestodes (tapeworms). It causes severe damage to the tapeworm's tegument (outer surface), disrupting calcium homeostasis and inducing rapid contraction and paralysis of the worm's musculature. The damaged tapeworm is then digested by the host's intestinal enzymes or passed in the stool.
The combination of these three drug classes is significant because it addresses parasites with entirely different biology — arthropods (fleas, ticks), nematodes (heartworm, roundworm, hookworm), and cestodes (tapeworms) — without requiring multiple separate medications.
Typical Dosage Range by Dog Weight
NexGard Plus is dosed according to body weight and comes in four chewable tablet strengths. The minimum effective dose targets approximately:
- Afoxolaner: 2.5 mg/kg (1.14 mg/lb)
- Moxidectin: 0.085 mg/kg (0.039 mg/lb) — note this is lower than some standalone moxidectin products
- Praziquantel: 2.5 mg/kg (1.14 mg/lb)
| Dog Weight Range | Afoxolaner | Moxidectin | Praziquantel | Chew Color Code |
|---|---|---|---|---|
| 4.4 – 10 lb (2 – 4.5 kg) | 11.3 mg | 0.38 mg | 11.3 mg | Green |
| 10.1 – 22 lb (4.6 – 10 kg) | 22.6 mg | 0.76 mg | 22.6 mg | Blue |
| 22.1 – 44 lb (10.1 – 20 kg) | 68 mg | 2.3 mg | 68 mg | Purple |
| 44.1 – 88 lb (20.1 – 40 kg) | 136 mg | 4.5 mg | 136 mg | Red |
Administration instructions:
- Frequency: Once monthly, year-round (heartworm prevention requires no seasonal gaps)
- With or without food: NexGard Plus can be given with or without food. However, giving with a meal may reduce the incidence of gastrointestinal side effects in sensitive dogs
- Duration: Continuous monthly administration for the dog's lifetime is recommended in heartworm-endemic areas (which, per the American Heartworm Society, now includes all 50 U.S. states)
- Chewable format: Most dogs willingly consume the beef-flavored chew as a treat. For dogs that refuse it, the chew can be hidden in a small amount of food, but ensure the entire chew is consumed — splitting the chew is not recommended as it may result in uneven drug distribution
Side Effects: What to Watch For
In pre-approval field studies and post-market surveillance, NexGard Plus demonstrated an acceptable safety profile for most dogs. However, as with any medication, adverse reactions can occur. Understanding the frequency and severity helps you know what warrants a phone call versus an emergency visit.
| Side Effect | Reported Frequency | Severity | Action Required |
|---|---|---|---|
| Vomiting | ~3.8% | Mild | Monitor; give future doses with food |
| Diarrhea / soft stool | ~2.7% | Mild | Monitor hydration; resolve within 24–48 hrs |
| Decreased appetite | ~1.5% | Mild | Monitor; consult vet if persists >48 hrs |
| Lethargy | ~1.2% | Mild to Moderate | Monitor; contact vet if severe or >24 hrs |
| Itching / skin irritation | ~0.9% | Mild | Monitor; may indicate dying flea reaction |
| Seizures / tremors / ataxia | Rare (<0.1%) | Serious | EMERGENCY — contact vet immediately |
| Allergic reaction (facial swelling, hives, difficulty breathing) | Rare | Serious | EMERGENCY — contact vet immediately |
🚨 Seek Immediate Veterinary Attention If Your Dog Exhibits:
- Seizures, muscle tremors, or loss of coordination (ataxia)
- Facial swelling, hives, or difficulty breathing (signs of anaphylaxis)
- Persistent vomiting (more than 2 episodes in 24 hours)
- Bloody diarrhea or black, tarry stools
- Complete refusal to eat for more than 48 hours
- Yellowing of the gums or whites of the eyes (icterus — potential liver involvement)
If you suspect a serious adverse reaction, contact your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 (24/7, consultation fee applies). You can also report adverse events to the FDA through their Safety Reporting Portal.
Important note on isoxazolines: The FDA has issued an advisory that isoxazoline-class drugs (including afoxolaner) have been associated with neurologic adverse events including muscle tremors, ataxia, and seizures in some dogs. Dogs with a pre-existing seizure disorder or history of neurologic conditions should be evaluated carefully before starting any isoxazoline product. Discuss this risk specifically with your veterinarian — alternative non-isoxazoline preventives may be more appropriate for these dogs.
Contraindications: Dogs Who Should NOT Receive NexGard Plus
NexGard Plus is not appropriate for every dog. Your veterinarian will screen for the following contraindications before prescribing:
- Age under 8 weeks: Safety has not been established in puppies younger than 8 weeks
- Weight under 4.4 lb (2 kg): The lowest available dose strength is formulated for dogs weighing at least 4.4 lb
- Known hypersensitivity to afoxolaner, moxidectin, praziquantel, or any excipients in the formulation
- Heartworm-positive dogs: NexGard Plus is a heartworm preventive, not a treatment. Dogs that test positive for adult heartworm infection (Dirofilaria immitis antigen-positive) require a separate adulticide treatment protocol (typically melarsomine injections). Administering a preventive to a heartworm-positive dog can trigger a severe reaction as microfilariae die rapidly
- Dogs with a history of seizures or epilepsy: Use with extreme caution and only under close veterinary monitoring. The isoxazoline class carries an FDA warning regarding neurologic adverse events
- MDR1 gene mutation (ABCB1-1Δ): Dogs carrying the MDR1 mutation (common in Australian Shepherds, Collies, Shetland Sheepdogs, and related herding breeds) have a compromised blood-brain barrier that can allow certain drugs, including macrocyclic lactones like moxidectin, to accumulate in the CNS at higher concentrations. While the moxidectin dose in NexGard Plus is generally considered safe even for MDR1-affected dogs at the labeled dose, your veterinarian may recommend genetic testing or an alternative product
- Breeding, pregnant, or lactating dogs: Safety has not been fully evaluated in these populations. Your veterinarian will weigh risks and benefits
Drug Interactions and Concurrent Medications
Before starting NexGard Plus, provide your veterinarian with a complete list of all medications, supplements, and over-the-counter products your dog receives. Known and theoretical interactions include:
⚠️ Significant Interactions
- Other macrocyclic lactones (ivermectin, milbemycin oxime, selamectin) — concurrent use increases risk of neurotoxicity, especially in MDR1-affected dogs
- High-dose ivermectin (used off-label for demodicosis) — additive CNS depression risk with moxidectin component
- Spinosad (Comfortis) — some reports suggest increased isoxazoline side effects when combined; monitor closely
⚡ Use With Caution
- Corticosteroids — may alter drug metabolism; monitor for increased side effects
- NSAIDs (carprofen, meloxicam, etc.) — no direct contraindication, but GI side effects from both medications can compound; give with food
- P-glycoprotein inhibitors (ketoconazole, itraconazole, cyclosporine) — may increase moxidectin CNS penetration
- Phenobarbital or potassium bromide (seizure medications) — the isoxazoline component may theoretically lower seizure threshold
Always consult your veterinarian before combining NexGard Plus with any other medication. Your vet may adjust timing, dosing, or recommend an alternative product based on your dog's complete medication profile.
Monitoring Requirements and Follow-Up
Recommended Monitoring Schedule
| Timeframe | Monitoring Action | Purpose |
|---|---|---|
| Before starting | Heartworm antigen test (4Dx or similar) | Confirm dog is heartworm-negative before starting preventive |
| First 48 hours post-dose | Owner observation | Watch for vomiting, diarrhea, lethargy, or neurologic signs |
| Annually | Heartworm antigen test | Verify continued heartworm-negative status despite prevention |
| Annually | Fecal flotation / parasite panel | Confirm intestinal parasite control; detect breakthrough infections |
| Every dose | Weigh your dog | Ensure correct dosage bracket — growing puppies or weight-changing dogs may need a different chew size |
| As needed | CBC/chemistry panel (vet discretion) | For dogs on long-term concurrent medications or with pre-existing liver/kidney conditions |
Annual heartworm testing is critical even when your dog is on year-round prevention. According to the American Heartworm Society guidelines, no preventive is 100% effective, and compliance gaps (missed doses, vomiting shortly after administration, drug interactions) can leave your dog vulnerable. Annual testing catches breakthrough infections early, when treatment is most successful.
Cost Range, Availability, and Generics
NexGard Plus is a relatively recent entry to the all-in-one preventive market, and pricing reflects its premium positioning. As of early 2026, here's what you can expect:
- 6-month supply: $85 – $130 depending on weight bracket and retailer
- 12-month supply: $155 – $245 depending on weight bracket
- Per-dose cost: approximately $13 – $21 per chew
Availability: NexGard Plus is available exclusively through licensed veterinarians and verified online veterinary pharmacies (those requiring prescription verification). Major online pharmacies such as Chewy Pharmacy, 1-800-PetMeds, and VetRxDirect carry it, but all require your veterinarian's prescription authorization before dispensing.
Generic availability: As of 2026, there are no FDA-approved generic equivalents of NexGard Plus. The afoxolaner patent provides exclusivity protection. However, some veterinary clinics offer comparable multi-parasite coverage through combination protocols (e.g., a standalone isoxazoline flea/tick product plus a separate heartworm/intestinal parasite preventive), which may be more cost-effective for some households.
Cost comparison context: Compared to purchasing three separate products for equivalent coverage (a flea/tick preventive + heartworm preventive + dewormer), NexGard Plus is often competitively priced and significantly more convenient. The convenience factor also improves compliance — studies show that simpler preventive regimens have higher owner adherence rates.
Missed Dose and Overdose Protocols
If You Miss a Dose
If you realize your dog's monthly NexGard Plus dose is late:
- Administer the missed dose as soon as you remember
- Resume monthly dosing from that new date (do not double-dose)
- If the gap between doses exceeds 8 weeks, contact your veterinarian — a heartworm antigen test may be recommended before resuming, as the protection window may have lapsed
- Set a recurring calendar reminder or use your vet's reminder app to prevent future gaps
If an Overdose Occurs
In safety studies, dogs were administered NexGard Plus at up to 5 times the maximum labeled dose without serious adverse effects. However, individual sensitivity varies. If your dog accidentally consumes more than the prescribed amount:
- Contact your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 immediately
- Monitor for vomiting, diarrhea, tremors, ataxia, or excessive salivation
- Do not attempt to induce vomiting unless specifically directed by a veterinary professional
- Bring the packaging with you to the vet so the exact ingested amount can be calculated
Alternatives to NexGard Plus
If NexGard Plus isn't the right fit for your dog — whether due to cost, contraindications, or your veterinarian's recommendation — several alternatives provide overlapping parasite coverage. Your veterinarian will help you choose based on your dog's risk profile, breed, and health history.
| Product | Fleas | Ticks | Heartworm | Intestinal Worms | Tapeworms | Format |
|---|---|---|---|---|---|---|
| NexGard Plus | ✅ | ✅ | ✅ | ✅ | ✅ | Oral chew |
| Simparica Trio | ✅ | ✅ | ✅ | ✅ | ❌ | Oral chew |
| Credelio Plus | ✅ | ✅ | ✅ | ✅ | ❌ | Oral chew |
| Interceptor Plus | ❌ | ❌ | ✅ | ✅ | ✅ | Oral chew |
| Heartgard Plus + NexGard (combo protocol) | ✅ | ✅ | ✅ | ✅ | ❌ | Two oral chews |
| Revolution Plus (topical) | ✅ | ✅ | ✅ | ✅ | ❌ | Topical spot-on |
NexGard Plus is currently the only single-chew product that includes tapeworm coverage (via praziquantel). If your dog is at risk for tapeworms — particularly dogs that hunt rodents, eat raw diets, or have flea infestations (fleas are the intermediate host for Dipylidium caninum) — this is a meaningful differentiator. For dogs with low tapeworm risk, products like Simparica Trio or Credelio Plus offer comparable coverage for the other parasite categories.
Frequently Asked Questions
How long does my dog need to be on NexGard Plus?
Heartworm prevention should be administered year-round for your dog's entire life, per the American Heartworm Society and the AVMA. Flea and tick prevention is similarly recommended year-round in most U.S. climates, as fleas can survive indoors through winter and tick activity has expanded with warming climate trends. Intestinal parasite coverage provides ongoing protection, particularly important for dogs that visit dog parks, boarding facilities, or interact with wildlife-adjacent environments.
Can I use NexGard Plus if my dog is on a raw diet?
Yes. NexGard Plus is effective regardless of diet type. However, if you feed a raw diet, the tapeworm coverage in NexGard Plus becomes especially relevant, as raw meat can be a source of Taenia and Echinococcus tapeworms. Discuss your dog's raw feeding practices with your veterinarian so they can assess overall parasite risk comprehensively.
My dog vomited within an hour of taking NexGard Plus. Should I re-dose?
Contact your veterinarian before re-dosing. As a general guideline, if vomiting occurs within 1 hour of administration, the full dose may not have been absorbed, and your veterinarian may recommend re-administration. If vomiting occurs 2 or more hours after administration, the drug is likely adequately absorbed, and re-dosing is typically unnecessary. Your vet will make the final determination based on your dog's specific situation.
Is NexGard Plus safe for MDR1-affected breeds like Australian Shepherds or Collies?
The moxidectin dose in NexGard Plus is relatively low compared to some standalone macrocyclic lactone products, and is generally considered safe at the labeled dose even for MDR1-affected dogs. However, the Washington State University Veterinary Clinical Pharmacology Lab, which maintains the MDR1 database, recommends that owners of affected breeds discuss the specific risks with their veterinarian. Some vets prefer to use non-macrocyclic lactone alternatives for known MDR1 homozygous-mutant dogs as an extra precaution.
Does NexGard Plus protect against all tick species?
NexGard Plus is labeled for four tick species: the American dog tick (Dermacentor variabilis), brown dog tick (Rhipicephalus sanguineus), Lone Star tick (Amblyomma americanum), and black-legged/deer tick (Ixodes scapularis). This covers the primary vectors for Lyme disease, Ehrlichiosis, Anaplasmosis, and Rocky Mountain Spotted Fever in the United States. However, no single product covers every tick species globally. If you travel with your dog to areas with different tick populations, discuss supplemental protection with your veterinarian.
Can NexGard Plus be used alongside vaccines?
There are no known interactions between NexGard Plus and canine vaccines. However, some veterinarians prefer to space preventive medications and vaccinations by 24–48 hours to make it easier to identify the cause if an adverse reaction occurs. Follow your veterinarian's specific guidance on timing.
Disclaimer: This article is for informational purposes only and does not replace professional veterinary advice. Always consult your veterinarian before starting, stopping, or changing any medication for your dog. Your veterinarian is the only qualified professional who can evaluate your dog's individual health needs and prescribe appropriate treatment.
Aaron Whyte
All our authors care for dogs every day — read more of their work on the authors page.
