Complete Prescription Guide
Complete guide to NexGard Plus flea and tick protection for dogs: dosage, side effects, drug interactions, cost, and vet-recommended alternatives.
This medication requires a veterinarian prescription and should only be used under veterinary supervision. Never administer NexGard Plus without a valid vet-client-patient relationship. Your veterinarian will determine the appropriate dosage based on your dog's weight, health status, and concurrent medications.
What Is NexGard Plus and What Is It Used For?
NexGard Plus is a beef-flavored, chewable parasiticide manufactured by Boehringer Ingelheim that combines three active ingredients — afoxolaner, moxidectin, and pyrantel — into a single monthly chewable tablet. While the original NexGard (afoxolaner only) covers fleas and ticks, NexGard Plus broadens coverage to include heartworm prevention and intestinal parasite control, making it one of the most comprehensive all-in-one preventives available by prescription in 2026.
The FDA's Center for Veterinary Medicine approved NexGard Plus for use in dogs and puppies 8 weeks of age and older, weighing at least 4 pounds (1.8 kg). It is classified under the isoxazoline drug class combined with a macrocyclic lactone and a tetrahydropyrimidine anthelmintic.
FDA-Approved Veterinary Uses
- Flea treatment and prevention — kills adult Ctenocephalides felis fleas and prevents egg laying for one month
- Tick control — effective against the Lone Star tick (Amblyomma americanum), American dog tick (Dermacentor variabilis), deer tick/black-legged tick (Ixodes scapularis), and brown dog tick (Rhipicephalus sanguineus)
- Heartworm disease prevention — kills tissue-stage larvae of Dirofilaria immitis
- Intestinal parasite treatment and control — adult roundworms (Toxocara canis, Toxascaris leonina) and hookworms (Ancylostoma caninum, Uncinaria stenocephala)
Common Off-Label Uses
Some veterinarians may prescribe NexGard Plus off-label for demodectic mange (Demodex canis) or sarcoptic mange (Sarcoptes scabiei) based on the afoxolaner component's documented efficacy against mites. However, these uses have not been formally approved by the FDA for this specific product formulation, and your vet will determine if this approach is appropriate for your dog's condition.
How Does NexGard Plus Work? Mechanism of Action
Three-Ingredient Mechanism Breakdown
Afoxolaner (Isoxazoline class): Binds to ligand-gated chloride channels in insect and acarine nervous systems, specifically targeting GABA-gated and glutamate-gated chloride channels. This causes uncontrolled neuronal excitation, seizures, and death in fleas, ticks, and mites. The compound is selective — mammalian GABA receptors have a different structure, which provides the safety margin for dogs.
Moxidectin (Macrocyclic lactone class): Interferes with glutamate-gated chloride channels in nematode nerve and muscle cells, causing hyperpolarization and flaccid paralysis. At the preventive dose, it targets L3 and L4 heartworm larvae before they mature into adults in the pulmonary arteries.
Pyrantel (Tetrahydropyrimidine class): Acts as a depolarizing neuromuscular blocking agent in susceptible intestinal nematodes, causing spastic paralysis. The paralyzed worms lose their grip on the intestinal wall and are expelled through normal peristalsis.
After your dog chews and swallows the tablet, afoxolaner is absorbed through the gastrointestinal tract and distributes into the skin and fat tissues, where it remains active for approximately 30 days. Moxidectin reaches peak plasma concentrations within 2-4 days and maintains therapeutic levels throughout the dosing interval. Pyrantel acts locally within the GI tract with minimal systemic absorption — which is why it's so well tolerated.
Typical Dosage of NexGard Plus by Weight
NexGard Plus is dosed by weight class using pre-measured chewable tablets. Your veterinarian will select the correct tablet size. The minimum effective doses are approximately:
| Dog Weight | Afoxolaner (mg) | Moxidectin (mcg) | Pyrantel (mg) | Tablet Color Code |
|---|---|---|---|---|
| 4 – 10 lb (1.8 – 4.5 kg) | 11.3 | 2.3 | 22.7 | Blue |
| 10.1 – 24 lb (4.6 – 10.9 kg) | 28.4 | 5.7 | 56.8 | Green |
| 24.1 – 60 lb (11 – 27.2 kg) | 68 | 13.6 | 136 | Orange |
| 60.1 – 121.5 lb (27.3 – 55.1 kg) | 136 | 27.2 | 272 | Purple |
Frequency: Once monthly, year-round. The American Heartworm Society recommends 12-month continuous prevention regardless of climate, as heartworm-carrying mosquitoes have been documented in all 50 U.S. states.
With or without food: NexGard Plus can be given with or without food. However, offering it with a meal may reduce the chance of mild GI upset in sensitive dogs. The beef-flavored chewable is designed to be readily accepted — in palatability studies, over 93% of dogs voluntarily consumed the tablet.
Side Effects of NexGard Plus: What to Watch For
Most dogs tolerate NexGard Plus well. In pre-approval field studies reviewed by the FDA, adverse reactions were infrequent and generally mild. However, as with any parasiticide, individual dogs may react differently.
| Side Effect | Reported Frequency | Severity | Typical Onset |
|---|---|---|---|
| Vomiting | ~3.0% | Mild | 1-4 hours post-dose |
| Diarrhea / loose stool | ~2.0% | Mild | 4-12 hours post-dose |
| Decreased appetite | ~1.5% | Mild | 1-6 hours post-dose |
| Lethargy / drowsiness | ~1.2% | Mild | 2-8 hours post-dose |
| Itching / skin irritation | ~1.0% | Mild to Moderate | 12-24 hours post-dose |
| Seizures / tremors | Rare (<0.1%) | Serious | 2-24 hours post-dose |
- Seizures, muscle tremors, or ataxia (stumbling, loss of coordination)
- Repeated vomiting (more than 2 episodes in 24 hours)
- Bloody or black, tarry diarrhea
- Facial swelling, hives, or difficulty breathing (possible allergic reaction)
- Complete refusal to eat for more than 24 hours
- Yellowing of gums or whites of the eyes (jaundice — rare liver involvement)
If you suspect an adverse reaction, contact your veterinarian or call the ASPCA Animal Poison Control Center at (888) 426-4435 (24/7, consultation fee applies) or the Pet Poison Helpline at (855) 764-7661.
Important note on isoxazolines: The FDA has issued an advisory that isoxazoline-class drugs (including afoxolaner) have been associated with neurologic adverse reactions — including muscle tremors, ataxia, and seizures — in some dogs. Dogs with a pre-existing seizure disorder or history of epilepsy should be monitored closely. Your veterinarian may recommend an alternative class of parasiticide for these patients. Consult the FDA's veterinary safety communications for the latest updates.
Contraindications: Which Dogs Should NOT Receive NexGard Plus
NexGard Plus is not appropriate for every dog. The following situations are contraindications or require careful veterinary risk-benefit assessment:
- Puppies under 8 weeks of age — safety has not been established in very young puppies
- Dogs weighing less than 4 lb (1.8 kg) — no appropriate tablet size exists; dosing accuracy cannot be guaranteed
- Dogs with a known seizure disorder or epilepsy — the isoxazoline component may lower the seizure threshold; your vet may prefer a non-isoxazoline alternative
- Dogs with known hypersensitivity to afoxolaner, moxidectin, or pyrantel — prior allergic reaction to any component is an absolute contraindication
- Heartworm-positive dogs — NexGard Plus is a preventive, not a treatment for adult heartworm infection. Dogs must be heartworm-tested negative before starting. Administering moxidectin to a dog with adult heartworms can trigger a dangerous microfilarial die-off reaction (anaphylaxis, circulatory collapse)
- MDR1 gene mutation carriers — Collies, Australian Shepherds, and related herding breeds with the MDR1 (ABCB1) gene mutation have increased sensitivity to macrocyclic lactones like moxidectin. At the approved preventive dose, NexGard Plus is generally considered safe even for MDR1 mutants, but your vet may recommend genetic testing through Washington State University's Veterinary Genetics Lab before prescribing
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:
| Concurrent Drug/Supplement | Interaction Type | Risk Level | Veterinary Guidance |
|---|---|---|---|
| Other macrocyclic lactones (ivermectin, selamectin, milbemycin) | Additive neurotoxicity risk | High | Do NOT combine — choose one heartworm preventive only |
| Spinosad (Comfortis) | May increase isoxazoline exposure | Moderate | Avoid concurrent use; choose one oral parasiticide class |
| Phenobarbital / potassium bromide (anti-seizure meds) | Hepatic enzyme induction may alter drug metabolism | Moderate | Vet monitoring required; efficacy of either drug may be affected |
| NSAIDs (carprofen, meloxicam, grapiprant) | No direct pharmacokinetic interaction documented | Low | Generally safe to co-administer; monitor for GI signs |
| Other pyrantel-containing products (Drontal, Nemex) | Duplicate anthelmintic dosing | Moderate | Avoid — NexGard Plus already contains pyrantel |
Critical rule: Never layer two heartworm preventives. If your dog is already on Interceptor Plus, Heartgard Plus, Simparica Trio, or Revolution Plus, your veterinarian will advise a safe transition protocol — typically finishing the current month's dose and switching to NexGard Plus at the next scheduled interval.
Monitoring Requirements and Follow-Up
| Monitoring Item | Frequency | Purpose | Estimated Cost |
|---|---|---|---|
| Heartworm antigen test (SNAP or lab-based) | Annually, or before starting | Confirm heartworm-negative status before prescribing moxidectin | $35 – $75 |
| Fecal flotation / parasite panel | Annually (puppies: every 3-6 months) | Verify intestinal parasite clearance | $25 – $55 |
| Weight check | Every 6 months or at each refill | Ensure correct dosage bracket — weight changes may require tablet size change | Usually included in wellness exam |
| MDR1 genetic test (if applicable breed) | One-time | Assess moxidectin sensitivity risk in herding breeds | $70 – $100 |
For dogs with a history of adverse reactions to parasiticides, your veterinarian may recommend a brief observation period after the first dose — administering the chewable during clinic hours so staff can monitor for 30-60 minutes.
Cost, Availability, and What to Do About Missed Doses
Pricing (2026 Estimates)
NexGard Plus is available exclusively through licensed veterinarians and verified online pet pharmacies (those requiring prescription verification). Typical retail pricing:
- Single monthly dose: $22 – $35 per chewable, depending on weight bracket
- 6-month supply: $125 – $190
- 12-month supply: $230 – $360 (many vets offer 12-packs with 2 free doses, effectively reducing per-dose cost)
As of 2026, there is no generic equivalent for the three-drug combination in NexGard Plus. Individual components (afoxolaner, moxidectin, pyrantel) are available in separate products, but the combined formulation remains under Boehringer Ingelheim's patent protection.
Missed Dose Protocol
If you miss a monthly dose, administer the chewable as soon as you remember and resume monthly dosing from that new date. However, there is a critical nuance with the heartworm component: if the gap between doses exceeds 45 days, the American Heartworm Society guidelines recommend:
- Administer the missed dose immediately
- Retest for heartworm antigen 6-7 months after the gap (because larvae acquired during the unprotected window may have matured)
- Continue monthly dosing without further interruption
A gap of less than 45 days generally does not compromise heartworm prevention efficacy, as moxidectin has a back-reach effect that can eliminate larvae acquired slightly before the previous dose.
Overdose Response
If your dog accidentally ingests more than the prescribed amount (for example, a small dog eating a large-dog tablet, or getting into the supply cabinet), take these steps:
- Do not induce vomiting unless directed by a veterinarian
- Note the exact amount consumed and the time of ingestion
- Call your veterinarian, an emergency veterinary clinic, or the ASPCA Animal Poison Control Center at (888) 426-4435 (24/7, consultation fee of approximately $95 applies)
- Monitor for vomiting, tremors, ataxia, or lethargy
In safety studies, dogs given up to 5× the recommended dose of afoxolaner showed no clinically significant adverse effects. However, overdose of the moxidectin component at high multiples could cause neurological signs, especially in MDR1-sensitive breeds.
How Long Does My Dog Need to Be on NexGard Plus?
Heartworm prevention is a year-round, lifelong commitment for most dogs in the United States. The American Heartworm Society and the American Veterinary Medical Association both recommend continuous 12-month prevention regardless of local climate, because:
- Mosquito vectors have been found active in winter months in many regions due to urban microclimates and climate variability
- Missed doses create dangerous protection gaps that are difficult to track
- The intestinal parasite and flea/tick components provide year-round health benefits
If you are considering discontinuing NexGard Plus — for example, due to cost concerns or a dog's adverse reaction — talk to your veterinarian about alternative products that cover the same spectrum of parasites. Stopping all prevention is not recommended in any U.S. state.
Alternatives to NexGard Plus
If NexGard Plus isn't the right fit for your dog, several prescription alternatives offer overlapping coverage. Your veterinarian will help select based on your dog's health profile, lifestyle, and your budget:
| Product | Fleas/Ticks | Heartworm | Intestinal Parasites | Form | Approx. Monthly Cost |
|---|---|---|---|---|---|
| Simparica Trio | ✓ (sarolaner) | ✓ (moxidectin) | ✓ (pyrantel) | Chewable | $20 – $32 |
| Credelio Plus | ✓ (lotilaner) | ✓ (moxidectin) | ✓ (pyrantel) | Chewable | $22 – $34 |
| Interceptor Plus | ✗ | ✓ (milbemycin) | ✓ (praziquantel — adds tapeworms) | Chewable | $12 – $22 |
| Revolution Plus (topical) | ✓ (selamectin + sarolaner) | ✓ (selamectin) | Partial (hookworms, roundworms) | Topical | $22 – $38 |
| NexGard (original) | ✓ (afoxolaner) | ✗ | ✗ | Chewable | $18 – $28 |
Key trade-off: Products like Interceptor Plus are significantly less expensive monthly but do not cover fleas and ticks, meaning you'd need to add a separate product (like Bravecto or Frontline) for full coverage. NexGard Plus consolidates everything into one chewable, which simplifies compliance — a real advantage if you've ever forgotten to give one of multiple separate medications on schedule.
Frequently Asked Questions
Can I buy NexGard Plus without a prescription?
No. NexGard Plus is classified as a prescription-only animal drug (Rx) by the FDA. Legitimate online pharmacies will require your veterinarian's authorization before dispensing. Any website selling NexGard Plus without a prescription is operating outside federal law and may be selling counterfeit, expired, or improperly stored product — which can be ineffective or dangerous.
Is NexGard Plus safe for puppies?
Yes, for puppies 8 weeks of age and older weighing at least 4 pounds. Safety studies in puppies from 8 weeks of age showed no adverse effects at the labeled dose. Always confirm your puppy's exact weight at each vet visit, as rapid growth may require moving to the next tablet size bracket.
Can I use NexGard Plus on my cat?
Absolutely not. NexGard Plus is formulated exclusively for dogs. Afoxolaner and moxidectin at canine doses can be toxic to cats. Never split a dog tablet to dose a cat. If you need flea, tick, and heartworm prevention for a cat, ask your veterinarian about feline-specific products like Revolution Plus or Bravecto Plus for cats.
My dog vomited within an hour of taking NexGard Plus. Should I redose?
If your dog vomits within 1-2 hours of administration, contact your veterinarian for guidance. Depending on how much of the chewable was visible in the vomit and the time elapsed, your vet may recommend redosing with a replacement tablet. Do not redose without veterinary direction, as double-dosing increases the risk of adverse effects.
Does NexGard Plus protect against tapeworms?
No. NexGard Plus covers roundworms and hookworms but does not contain praziquantel, the drug needed to treat tapeworms (Dipylidium caninum, Taenia spp., Echinococcus spp.). If your dog has a confirmed or suspected tapeworm infection, your veterinarian will prescribe a separate dewormer like Droncit or Drontal Plus.
Can NexGard Plus be used in pregnant or breeding dogs?
The safety of NexGard Plus has not been evaluated in pregnant, lactating, or breeding dogs. If your dog is pregnant or you plan to breed her, discuss alternative parasite prevention options with your veterinarian. Some individual components (like pyrantel) have established safety in pregnancy, but the combination product has not been formally tested in this population.
How should I store NexGard Plus?
Store at or below 30°C (86°F), with brief excursions up to 40°C (104°F) permitted. Keep the tablets in their original packaging until use, away from moisture and direct sunlight. Do not store in bathrooms or vehicles where humidity and temperature fluctuate significantly. Always keep out of reach of children and pets — the beef flavoring is intentionally appealing to dogs.
- NexGard Plus covers fleas, 4 tick species, heartworm, roundworms, and hookworms in one monthly chewable
- Prescription required — always use through a licensed veterinarian
- Not for dogs with seizure disorders without careful vet risk assessment
- Annual heartworm testing is mandatory before and during use
- Year-round, continuous use is recommended in all U.S. states
- If a dose is missed, give it immediately and consult your vet if the gap exceeded 45 days
Dr. Hannah Wickes
All our authors care for dogs every day — read more of their work on the authors page.
