Nexgard vs. Simparica: 2024 Comparison and Key Differences

Fleas are nearly impossible to detect until you notice that your pet is itching, scratching, and shows signs of discomfort. If you have more than one pet, it won’t take long before one gives fleas to the other. Seeing your pet scratch and suffer is heartbreaking. So, what do you do? Call your vet and get a prescription that works quickly and consistently.

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Flea medications come in various styles and sizes. Some last for a day, others last for significantly longer. There are some medications that both dogs and cats can take, and others designed just for specific animals. Pet owners can give doses of flea meds as chewable tablets, topical locations and sprays, and collars.

Along with the way flea medications are given, other notable differences include the active ingredients. Most have a poison that is safe for pets, but dangerous for fleas, ticks, and other parasites. These ingredients have side effects that could happen shortly after pet owners treat flea infestations.

Flea medications have a variety of price points. Usually, the products that last the longest have the highest up-front cost. But when you break down the cost over months, weeks, or days, long-term treatments tend to be the most affordable. Since there are so many options, you should be able to find one that is affordable and effective.

What to look for in a good flea treatment

When you need an effective flea treatment, you want one that gives relief as soon as possible. Some pet owners buy once-daily treatments that kill fleas within an hour. Then, they purchase long-term medications that are more affordable in the long run.

The best treatments should be easy to administer. If the medication tastes bad or is uncomfortable for your pet, it will fight you on it. Some of the best treatments taste like popular food flavors. Others are flavorless. Some of the topical medications feel soft and smooth when applied. Buy a treatment that does not create stress for you or your fur baby.

Another useful feature of some flea treatments is killing several parasites. Pets don’t just suffer from flea infestations. They can get worms, ticks, and other pests, too. If you can save money by buying a combo treatment, why wouldn’t you?

Flea treatments come in different dosages for different sizes of dogs and cats. Be sure that you buy a product that is appropriate for your pet’s weight and age. You could underdose or overdose your pet if you do not pay attention to the packaging, or if you guess your pet’s weight.  It is also essential to only give cats meds made for them.

Nexgard and Simparica Similarities

Nexgard and Simparica are made only for dogs. They are also both chewable tablets that rapidly kill fleas. They both kill four types of ticks, too. Both medications can be given with or without food.

Both medications have similarly mild side effects. As these are oral medications, some dogs react to the active ingredients by vomiting or developing diarrhea. Fortunately, side effects are rare, and if they do occur, they do not last long. The side effects are due to neurotoxins that kill the parasites.

The two medications have monthly doses. They both last at least one month, with Simparica lasting a few days longer than Nexgard, which gives you a bit of a cushion if you forget to give a dose. Both medications have minimum ages, and neither are designed for newborn puppies.

Dogs tend to like oral medication that tastes good. Both Nexgard and Simparica are flavored like favorite meat treats; Simparica tastes like beef, and Nexgard tastes like liver. Most dogs like one flavor or the other.

Veterinarians must prescribe these FDA-approved treatments. You should not give these medications to cats. Dogs and cats have different physiologies, so if you give a dog medication to a cat, you could accidentally poison the cat. If you have a cat and you need flea medication, your veterinarian can prescribe a safe one.

Nexgard and Simparica Differences

Nexgard and Simparica are made only for dogs. They are also both chewable tablets that rapidly kill fleas. They both kill four types of ticks, too. Pet owners can give both medications with or without food.

Simparica uses a neurotoxin called sarolaner. It is in the same class of toxin as Nexgard, and it works similarly. But, sarolaner works quicker and lasts longer than afoxolaner. The Simparica dosages last for 35 days, while the Nexgard doses last for 28. Afoxolaner is more effective at killing ticks that afoxolaner, too.

You cannot give Simparica to dogs until they reach six months of age. Veterinarians prescribe Nexgard to dogs that are two months old. So, many vets prescribe Nexgard for four months, until dogs reach six months, then they switch to Simparica as it offers more effective coverage.

While both medications have similar digestive side effects, they both have slightly different rare effects. Nexgard can cause lethargy and a loss of appetite in dogs. It can also cause seizures and tremors, but those side effects are incredibly rare. Simparica can cause ataxia, which is the official name for loss of body control.

Another difference is flavor. Both taste like meat, but dogs usually like the liver taste of Nexgard over the beef flavor of Simparica.

Even though younger dogs can safely take Nexgard, smaller dogs can safely take Simparica. Dogs that weigh at least 2.8 pounds can take Simparica, which dogs need to weigh four pounds to take Nexgard.

Nexgard and Simparica Pricing Comparison

Simparica is given once every five weeks. The medication includes six doses; each dose lasts up to five weeks. The weekly price is between $2.80 and $3.32.

Nexgard is given every four weeks. Each package includes six doses. The weekly prices range between $2.33 and $2.37.

The math doesn’t lie. Nexgard is less expensive, but the coverage for Simparica is better and lasts longer. The weekly cost varies by a few cents, especially for smaller dogs. But, if you need to watch your budget, Nexgard is a good choice for dogs that are two months old and weigh at least four pounds.

Our Review of Nexgard and Simparica

Simparica is a better medication for fighting fleas and ticks. But, veterinarians cannot prescribe it until dogs are six months old. Many pet owners decide to give their fur babies Nexgard once they reach two months of age. Then, as soon as their dogs are six months old, they switch to Simparica.

The most common reason that pet owners and veterinarians prefer Simparica is the length and breadth of its effectiveness. After 30 days, Simparica kills 95 percent of fleas and ticks. Nexgard does not last as long or provide the same powerful performance.

When comparing the prices of Nexgard and Simparica, they are close. Simparica does cost more per box, but the weekly price differences are between $.50 and $1.00. The coverage from Simparica is worth the added cost.

It is important to remember that cats cannot take either of these flea medications. The two medications are only for dogs. You could harm your cat if you gave them Simparica or Nexgard.

If your dog has a history of seizures, you should talk to your veterinarian before you ask for Simparica or Nexgard. This class of neurotoxins can occasionally cause tremors and seizures, and those side effects happen more often in pets who have histories of them.

Flea Treatment FAQs

How do neurotoxins affect fleas?

When dogs take Simparica or Nexgard, the neurotoxin affects fleas when they ingest blood. Then, the medication stops the fleas from being able to eat blood anymore and to reproduce. These two neurotoxins are so effective because they prevent adult fleas from reproducing, and they kill the other stages of fleas, from egg, larvae, and pupae.

Do all of my pets need flea treatments?

If you want to keep fleas off of your pets, they all need to be treated. If one pet has fleas, you can trust that your others will get them. Pets have different reactions to fleas, and those with flea allergies will itch and scratch more than fur babies without allergies.

Your dogs might have fleas, and you wouldn’t know because they haven’t scratched. Preventing fleas with medications like Nexgard or Simparica are the best ways to keep fleas of your dogs and out of your home.

Can I use the same medication on all of my pets?

No. Flea and tick medications are designed for different animals, ages, and weights. You should not give a small dog a large-dog dosage. And, you should not give a cat medication made for a dog. Read the boxes carefully, so you are sure you get the correct medicine for your fur baby.

How quickly will flea treatments kill fleas?

Some medications will kill fleas within 30 minutes. The dead fleas are usually adult fleas, and the dead fleas can make dogs itch even more. Eventually, the fleas will fall off of your dog.

Medications that treat younger fleas usually take longer to be effective. Your dog’s discomfort should end within a few days, if not sooner. If this doesn’t happen, contact your veterinarian.

What side effects can I expect to see?

Most dogs do not have any side effects after ingesting an oral treatment. If your dog does have a side effect, it will probably be vomiting or diarrhea. The side effects should only last a day or less, and often they happen right after ingesting the medication, and that’s it.

Pay attention to what your dog vomits, because it could be the entire tablet. Talk to your veterinarian if that happens.

Other side effects are rarer. They can include problems like lethargy, scratching, and ataxia. The most severe side effects are tremors and seizures. Most side effects do not require treatments to stop them, but if they do not stop, contact your veterinarian.


Your veterinarian is the best person to recommend a flea and tick medication for your fur baby. But, you have a choice in the matter. You can decide on a drug that fits your budget and takes care of the parasites that bother your dog. You also have to choose a medicine that your dog will take without problems.

Simparica is a medication that effectively kills fleas and ticks for over one month. Nexgard kills fleas and ticks for a month. The two drugs have different options for weight ranges. Always choose the medication that correlates with your pet’s size; otherwise, you could accidentally overdose your fur baby.

Without a flea and tick treatment, your fur baby could become sick. When parasites infect your dog, other parasites like tapeworms can also get into your pet’s body. Both Nexgard and Simparica keep fleas and ticks off of your dog.

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