Parasite control is an essential part of responsible dog ownership, particularly in regions where fleas and ticks are a year-round concern. In the United States, many pet owners turn to oral treatments as a modern alternative to traditional collars or topical products. One of the most discussed names in this category is Nexgard, an oral chewable designed specifically for flea and tick control in dogs.

This article takes an in-depth and objective look at Nexgard, including how it works, its target parasites, safety profile, dosing guidelines, and its role in broader veterinary care. It avoids any promotional language or brand endorsement and aims to provide factual information for dog owners, veterinary professionals, and anyone interested in understanding the role of monthly oral treatments in parasite prevention.

Understanding the Need for Flea and Tick Prevention

Fleas and ticks are more than just an inconvenience. These parasites can cause serious health issues in dogs, ranging from skin infections and allergic reactions to life-threatening diseases. In the United States, tick-borne illnesses such as Lyme disease, ehrlichiosis, and anaplasmosis have become increasingly prevalent, particularly in the Northeast, Midwest, and parts of the South.

Fleas, on the other hand, are responsible for flea allergy dermatitis, tapeworm infections, and can cause anemia in young or small dogs. Because of the health risks associated with these pests, year-round flea and tick control is now widely recommended by veterinarians across the country.

Oral medications like Nexgard are part of this preventive strategy, offering a systemic solution that targets parasites from the inside out.

What Is Nexgard?

Nexgard is a monthly oral treatment prescribed to dogs for the prevention and control of flea and tick infestations. It comes in a soft, chewable tablet that is flavored to encourage easy consumption. Unlike topical products that are applied directly to the skin, this medication works systemically—meaning that the active ingredient is absorbed into the dog’s bloodstream after ingestion.

Once a parasite bites the treated dog, it is exposed to the active compound, which quickly acts on the nervous system of the parasite, causing death. This mode of action allows for rapid elimination of fleas and ticks, often within hours.

How Nexgard Works

The key to Nexgard’s effectiveness lies in its active ingredient, which belongs to a class of compounds known as isoxazolines. These chemicals interfere with the nervous system of invertebrates like fleas and ticks by blocking specific neurotransmitters. When a parasite feeds on a treated dog, it ingests the active ingredient and succumbs to its effects—typically resulting in death before the parasite can reproduce or transmit disease.

Importantly, this action occurs only after the parasite bites and begins feeding. While this means the product does not prevent bites outright, it significantly reduces the risk of infestation and disease transmission by killing the parasites rapidly.

Parasites Targeted by Nexgard

Nexgard is effective against several key ectoparasites commonly found in the United States. These include:

• Fleas (Ctenocephalides felis) – Begins killing fleas within four hours and eliminates adult fleas before they can lay eggs.

• Black-legged ticks (Ixodes scapularis) – Known carriers of Lyme disease.

• Lone star ticks (Amblyomma americanum) – Associated with ehrlichiosis and other infections.

• American dog ticks (Dermacentor variabilis) – Can transmit Rocky Mountain spotted fever.

• Brown dog ticks (Rhipicephalus sanguineus) – Found in both indoor and outdoor environments.

This broad-spectrum activity makes Nexgard suitable for regions where multiple tick species are active.

Administration and Dosage

Nexgard is administered once per month, ideally on the same day each month to maintain consistent protection. The chewable tablet is available in multiple strengths, with dosages tailored to the weight of the dog. It is approved for use in dogs as young as 8 weeks old and weighing at least 4 pounds.

Owners should ensure that the entire chewable is consumed in one sitting. If the dog vomits shortly after administration or fails to ingest the full dose, veterinary guidance is recommended.

Because the medication is systemically distributed, it is not affected by bathing, swimming, or exposure to rain—unlike some topical options that can wash off or degrade with time.

Safety and Side Effects

Clinical trials and post-market data suggest that Nexgard is generally well tolerated by most dogs. However, as with any pharmaceutical product, some adverse effects have been reported. Common side effects may include:

• Vomiting

• Diarrhea

• Lethargy

• Loss of appetite

• Itching or skin irritation

Rare but more serious reactions—such as neurological symptoms (tremors, incoordination, or seizures)—have also been noted, particularly in dogs with a pre-existing history of seizures or neurological disorders. Though these events are uncommon, owners of dogs with such conditions should consult their veterinarian before beginning treatment.

Veterinarians evaluate each dog’s medical history and risk factors before prescribing the product to ensure it is safe and appropriate.

Veterinary Recommendations in the United States

Veterinarians across the U.S. often include oral flea and tick preventives as part of a dog’s comprehensive wellness plan. Oral products are particularly beneficial in households where topical application is impractical or where dogs regularly bathe, swim, or are groomed frequently.

Nexgard is commonly prescribed as a monthly option, often alongside a separate heartworm preventive. While it does not protect against internal parasites or heartworms, it fits well into a two-product protocol—one for external parasites and one for internal parasites like heartworm, roundworms, and hookworms.

The American Veterinary Medical Association (AVMA) and the Companion Animal Parasite Council (CAPC) both recommend year-round flea and tick control, regardless of geography or season, due to changes in climate patterns and parasite behavior.

Comparison with Other Flea and Tick Control Methods

There are several types of flea and tick control products available in the U.S., including:

• Topical treatments – Applied to the skin, often combining flea, tick, and sometimes internal parasite control.

• Collars – Offer extended protection but may not be suitable for all pets.

• Injectable or long-lasting oral medications – Require fewer doses per year but may have higher up-front costs.

• Combination medications – Protect against fleas, ticks, heartworms, and intestinal worms in one chew.

Each option has benefits and drawbacks. Nexgard, as an oral-only, flea and tick-specific medication, is often chosen for its convenience and effectiveness, particularly in dogs with skin sensitivities or active lifestyles.

Veterinarians help owners decide which product or combination of products best fits their dog’s needs based on factors like age, weight, health status, environment, and owner preferences.

Environmental Considerations and Regional Risk

Flea and tick populations are not evenly distributed across the United States. In high-risk areas—such as the Southeast, Northeast, and Midwest—year-round exposure to ticks and prolonged flea seasons increase the need for consistent protection.

Some tick-borne diseases, like Lyme disease, are especially common in the northeastern U.S., while others, like ehrlichiosis, are more widespread in the South and Midwest. Fleas are ubiquitous in most climates and can thrive indoors, making them a concern even in colder months.

Using products like Nexgard consistently each month helps mitigate these risks, regardless of region.

Storage, Handling, and Disposal

Like all medications, Nexgard should be stored at room temperature, out of reach of children and pets not being treated. Unused or expired doses should be disposed of according to local regulations or returned to a veterinary clinic for proper handling.

Dog owners should always check expiration dates before use and avoid administering doses meant for other dogs, particularly those of different weights.

Conclusion

Flea and tick prevention is a critical component of modern veterinary care. Products like Nexgard, which offer convenient, systemic protection against multiple ectoparasites, have become widely used across the United States. While no medication is without potential risks, the benefits of parasite prevention—such as reduced disease transmission and improved quality of life—are well established.

When used as directed and under the supervision of a veterinarian, monthly oral treatments provide a reliable defense against some of the most common threats to canine health. Understanding how these products work, what they target, and how to use them properly is key to making informed decisions about pet care.

By staying vigilant and working closely with veterinary professionals, pet owners can help ensure that their dogs remain protected, healthy, and comfortable throughout the year.