Nexgard Spectra’s formula is built around two primary active ingredients that target parasites through different mechanisms. The other “ingredients” of nexgard spectra are largely inactive fillers, binders, and flavorings that create the palatable chew.
1. Afoxolaner: The Primary Ectoparasiticide
What it is: The first active ingredient, belonging to the isoxazoline class.
How it Works: Afoxolaner is a potent insecticide and acaricide. It selectively binds to GABA-gated chloride channels and glutamate-gated chloride channels (GluCls) in the nerve and muscle cells of invertebrates (fleas, ticks, mites). This binding inhibits the passage of chloride ions, leading to uncontrolled hyperexcitation of the nervous system, paralysis, and death of the parasite.
Parasites it Eliminates:Fleas (Ctenocephalides felis), Black-legged tick (Ixodes scapularis), American Dog tick (Dermacentor variabilis), and Brown Dog tick (Rhipicephalus sanguineus).
2. Milbemycin Oxime: The Primary Endoparasiticide
What it is: The second active ingredient, belonging to the macrocyclic lactone class.
How it Works: Milbemycin oxime works by increasing the permeability of the cell membranes of parasitic worms to chloride ions. This leads to paralysis of the pharynx (inhibiting feeding) and body wall muscles, causing the parasites to detach and be expelled from the host’s gastrointestinal tract.
Parasites it Eliminates: Prevents Heartworm disease (Dirofilaria immitis) and treats and controls Roundworm (Toxocara canis, Toxascaris leonina) and Hookworm (Ancylostoma caninum, Uncinaria stenocephala) infections.
3. Microcrystalline Cellulose
What it is: A refined plant-based polymer used as a binder and filler.
How it Works: It provides bulk and structure to the chewable tablet, ensuring consistent distribution of the active ingredients. It helps create a stable, solid form that doesn’t crumble easily.
4. Croscarmellose Sodium
What it is: A cross-linked polymer of carboxymethylcellulose sodium, used as a disintegrant.
How it Works: It aids in the rapid breakdown of the chewable tablet in the dog’s stomach. This is crucial for ensuring the active ingredients (afoxolaner and milbemycin oxime) are quickly released and absorbed into the bloodstream.
5. Povidone
What it is: A synthetic polymer used as a binder.
How it Works: It helps to cohesively bind all the powdered ingredients together during the manufacturing process, ensuring the chew maintains its shape and each piece contains the correct, uniform dose of medication.
6. Stearic Acid
What it is: A common saturated fatty acid derived from animal or vegetable fats.
How it Works: It acts as a lubricant and emulsifier in the manufacturing process, preventing the ingredients from sticking to machinery. It also contributes to the texture and mouthfeel of the final product.
7. Silica Colloidal Anhydrous
What it is: A fine, powdered form of silicon dioxide.
How it Works: It functions as an anti-caking agent, preventing the powdered ingredients from absorbing moisture from the air and clumping together, which ensures the stability and shelf-life of the product.
What it is: A proprietary blend of palatability enhancers.
How it Works: This is a critical “inactive” ingredient. The beef flavoring makes the chew highly palatable, encouraging dogs to voluntarily consume it as a treat. This guarantees ingestion of the full dose and eliminates the stress of pilling.
9. Magnesium Stearate
What it is: A salt of magnesium and stearic acid.
How it Works: It acts primarily as a lubricant during the manufacturing process, ensuring the mixture flows smoothly and can be accurately pressed into chews without sticking to the equipment.
10. Sucrose
What it is: Common table sugar.
How it Works: It is used in a small quantity as a sweetening agent to further enhance the palatability of the chew, making it more appealing to dogs.
Summary Table: The Two-Pronged Attack on Parasites
Ingredient
Category
Primary Target
Mechanism of Action
Afoxolaner
Active
External Parasites (Fleas, Ticks)
Binds to nerve receptors, causing hyperexcitation, paralysis, and death.
Increases cell membrane permeability to chloride ions, causing paralysis and expulsion.
Microcrystalline Cellulose
Inactive (Filler/Binder)
N/A
Provides structure and bulk to the chew.
Croscarmellose Sodium
Inactive (Disintegrant)
N/A
Helps the chew break down quickly in the stomach for absorption.
Povidone
Inactive (Binder)
N/A
Binds ingredients together during manufacturing.
Stearic Acid
Inactive (Lubricant)
N/A
Prevents sticking during manufacturing.
Silica Colloidal Anhydrous
Inactive (Anti-caking)
N/A
Prevents moisture absorption and clumping.
Artificial Beef Flavor
Inactive (Palatability)
N/A
Makes the chew tasty for easy administration.
Magnesium Stearate
Inactive (Lubricant)
N/A
Ensures smooth manufacturing.
Sucrose
Inactive (Sweetener)
N/A
Enhances palatability.
Conclusion: The power of Nexgard Spectra lies in the synergistic combination of Afoxolaner and Milbemycin Oxime. Afoxolaner works from the inside-out, killing external parasites that bite, while Milbemycin Oxime works inside the body to prevent heartworm and eliminate intestinal worms. The remaining ingredients are essential for creating a safe, stable, and palatable delivery system that ensures dogs consume the full dose and receive complete protection.
Important Disclaimer: Nexgard Spectra is a prescription-only flea and worm treatment product. Always consult your veterinarian to ensure it is the right choice for your dog. Provide a full health history, and be aware of potential side effects, which can include vomiting, itching, lethargy, diarrhea, and, in rare cases, neurological signs such as tremors or seizures.
