Yes, NexGard requires a prescription from a veterinarian. All NexGard products, including NexGard Plus and NexGard Combo, are classified as prescription medications by the FDA, meaning you cannot legally purchase them without a vet’s authorization. This applies whether you buy directly from your vet’s office or through an online pharmacy like Chewy.
Why NexGard Requires a Prescription
NexGard belongs to the isoxazoline class of parasiticides, which work by targeting the nervous system of fleas and ticks. Specifically, the active ingredient (afoxolaner) blocks certain nerve receptors in parasites, causing paralysis and death. Because this mechanism involves neurological activity, the FDA requires veterinary oversight before dispensing the drug.
A vet needs to evaluate your dog before prescribing NexGard for a few practical reasons. The product is dosed by weight, with six different size categories ranging from 4 to over 132 pounds. An incorrect dose could be ineffective or harmful. NexGard Plus, the version that also prevents heartworm, requires a negative heartworm test first, because giving heartworm prevention to an already-infected dog can cause serious complications. Your vet also needs to assess whether your dog has a history of seizures or other neurological issues that might make an alternative product a better choice.
How to Get a Prescription
The process is straightforward. Schedule a routine wellness visit or a specific appointment to discuss parasite prevention. Your vet will weigh your dog, run a heartworm test if needed, and write a prescription on the spot. Most vet clinics stock NexGard and can sell it to you directly.
If you prefer to shop around for a better price, ask your vet to send the prescription to an online pharmacy. Retailers like Chewy accept vet prescriptions and will verify them before shipping. A six-month supply of NexGard for a mid-sized dog (10 to 24 pounds) runs about $164, while a 12-month supply costs roughly $329. Prices vary by weight category and retailer.
NexGard Product Versions
There are several NexGard formulations on the market, and all require a prescription. The differences come down to what parasites they cover.
- NexGard (original): Kills fleas and ticks. Contains afoxolaner only.
- NexGard Plus: Covers fleas, ticks, heartworm prevention, and intestinal worms (hookworms and roundworms). Adds two additional active ingredients to afoxolaner.
- NexGard Combo: Designed for cats. Kills fleas and ticks and prevents heartworm. Uses a slightly different formulation than the dog versions.
NexGard Plus has largely replaced the original NexGard as the go-to option for dogs, since it rolls flea, tick, and heartworm protection into a single monthly chew. It’s approved for puppies as young as eight weeks old, as long as they weigh at least four pounds.
How Quickly It Works
NexGard starts killing fleas within four hours of your dog eating the chew, reaching 99% effectiveness by the eight-hour mark. Ticks take longer, with most dying within 48 hours, though some are killed in as little as 8 to 12 hours. The protection lasts a full month per dose.
Safety Considerations
The FDA considers isoxazoline products, including NexGard, safe and effective for dogs and cats. However, the agency has issued an alert noting that some animals have experienced neurological side effects, including muscle tremors, loss of coordination, and seizures. These reactions are uncommon, and seizures have occurred even in animals with no prior history of neurological problems. If your dog has a seizure disorder, your vet may recommend a different type of flea and tick prevention.
Risks of Buying Without a Prescription
Some international websites sell NexGard or NexGard Spectra (a formulation not FDA-approved in the U.S.) without requiring a prescription. This is risky for several reasons. The EPA has flagged widespread counterfeiting of pet parasite products, with fake versions showing up in packaging that lacks English directions, child-resistant packaging, or correct dosing information. Foreign-labeled products sometimes use different units of measure, and the product inside may not match what’s shown on the box.
Counterfeit products also pose direct safety risks. Some dog formulations are toxic to cats, and without proper labeling, a mix-up could be fatal. If a child accidentally opens a package that lacks child-resistant packaging, there may be no first-aid instructions available. The safest route is always through your vet or a licensed U.S. pharmacy that verifies prescriptions.