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Comfortis Flea Pills for Dogs: Better Than Lufenuron

Laura is an avid pet lover. She is an advocate for pet adoption and senior pets. She has multiple cats and a sweet old lady poodle mix.

The Greatest Flea Treatment: Pills

Taking a pill to get rid of fleas is one of the great flea treatment options that dog owners have. Unlike topical products or flea collars, there is less risk of residue coming into contact with humans and less risk of it being washed off during routine grooming or if the dog gets wet in the rain.

In the past, the best flea pill option was one that contained the active ingredient Lufenuron. Than another pill emerged that was called Comfortis. This once-a-month pill has basically replaced Lufenuron. However, you can still purchase the old medication online.

So is Comfortis for dogs worth it? Is Lufenuron the way to go? Here are the pros and cons of each product and which one you should give your dog.

Understanding the Life Cycle of a Flea

To understand flea pills, you must first understand the life cycle of a flea.

An adult flea, like one that might jump on your dog when it is outside or comes into contact with an infestation, can lay hundreds of eggs. But in order to develop those eggs, she needs the nutrients found in your pet's blood.

After biting and feeding on your pet (causing the itching), she lays eggs. These eggs can be laid on your pet or in out of the way places where you pet stays (like in its bedding). Once the larva hatch, they feed on residue and waste until they become a mature flea, ready to find a mate and some blood.

Then the whole process starts again.

Not only do fleas cause itching and irritation for your dog, they can also cause problems such as tapeworms—an added worry and expense to treat.

So the best way to treat fleas is to stop this lifecycle.

Life cycle of a flea and tapeworms.

Life cycle of a flea and tapeworms.


Lufenuron used to be the active ingredient in monthly flea pills. This was the first kind of oral medication designed to control fleas.

The medicine (which also came in liquid form) would not treat live fleas, however. It was designed to control the fleas by making their eggs nonviable. So living fleas would go through their life cycle but they would not be able to produce more fleas.

The problem with this was that the dog could still suffer from fleas for weeks to months after the pill was administered if the home or yard had a flea infestation. Very often the pill would need to be given with a topical medication or some other pill in order to give the dog relief and control the fleas.

If the dog was exposed to a new infestation (such as when it went for a walk in the woods with its owner), then the whole process of fleas would start again.

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So while in some situations the flea medication could help with flea problems, it definitely had its limitations.

The best aspect of the product is that it was over the counter. The dog owner didn't have to take it to the vet to get the product.

You can still find the product in generic form in places.

New Lufenuron Pill

Most of the Lufenuron pills available today either contain or recommend that you dose the dog with an additional ingredient: Nitenpyram.

Nitenpyram is the ingredient found in the 24-hour over the counter flea pill Capstar. This pill kills all living adult fleas on the dogs for 24 hours.

The idea is that the two ingredients will work together to kill the fleas. However, in reality, your dog will likely still suffer from fleas for an extended period of time when taking this medication. It will work best if the dog is inside and does not go into areas where it may get a new exposure to fleas.

Pros and Cons of Lufenuron



Does not kill adult fleas

Easy to administer

Does not prevent new infestations

Can be used with Capstar or Topical

Need other medication to give dog relief

Comfortis works great for dogs.

Comfortis works great for dogs.

Comfortis Dogs

So, the flea pill product line was ready for something better. Eventually, a new flea pill emerged: Comfortis.

Comfortis flea pills contain Spinosad, which is an ingredient that kills any adult fleas that try to bit the dog. The pill continues to kill any new fleas for an entire month. Comfortis has revolutionized the way flea pills work and can even be used for cats as well.

The flea pill can also be used in conjunction with a topical flea medication such as Revolution. This is especially helpful if your dog suffers from irritation or allergies caused by flea bites. But if the product gets washed off during grooming, your dog is still protected by the Comfortis pill.

The downside of Comfortis is that you can only get it from your vet via a prescription. So if your dog is not up to date in its vaccinations and yearly vet visits, then you will not be able to get the product.

Pros and Cons of Comfortis


Works for a full month

Vet prescription only

Can be used with topical

More expensive than some over the counter brands

Won't wash off

May cause stomach upset

Kills adult fleas

Side Effects?

Any time you choose to give your dog medication, either over the counter or prescription, you should check with your vet and watch for adverse reactions. Both of the pills can cause an upset stomach. It is recommended that you give them the pill with food.

Some dogs may suffer from long-term stomach problems or other issues.

For my dog, I found that he is likely to have a loose stool or two for the day or two after administration of the pill. He otherwise seems to have no adverse effects and the pills worked to curb even a bad flea infestation.

There is no reason to let your dog suffer with fleas.

There is no reason to let your dog suffer with fleas.

Best Ways to Give a Flea Pill to Dogs

Some dogs will readily eat anything and others are very picky and suspicious. Since both pills recommend that the dog have a full stomach, make sure it eats before you give them the pill. You can then try putting the pill in a pill pocket or even wrapping it in a bit of bread or lunch meat. The idea is to disguise it so the dog will readily accept it.

If your dog still won't take it, you can even grind it up into some canned food. Just make sure that they eat the entire meal in order to get the full effects.

Overall Recommendation

With the emergence of Comfortis, a more effective product was born. It is definitely worth the trip to the vets, especially if you are suffering from a flea infestation that doesn't want to stop.

If a vet trip is not possible and you want to try the Lufenuron, I recommend purchasing some Capstar pills. Give those to the dog every few days to kill the adult fleas. Additionally, you can also purchase effective over the counter topicals such as Advantage and Revolution. Using these in conjunction with the Lufenuron may be more effective in the long run. Or skip the Lufenuron and just use topicals. The results may not be very different.

As always, if you are in doubt about how your dog will handle any flea medication, it is best to consult a licensed vet about your dog's particular needs.

Fleas should not cause you or your dog frustration. There are many great options out there that can make your dog and your home flea-free!

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

Question: How good is generic Frontline for dogs over 50 lbs?

Answer: I've always had good luck with the generic versions of some of the more popular medications. If you are concerned, always ask your vet before trying a new product.


L C David (author) from Florida on November 11, 2013:

It really is great that there are so many good flea control choices that were not available even a decade ago. After a particular tough bout with fleas this summer I've tried many products. I found that Comfortis helped to finally kill those pesky ones that just wouldn't quite go away.

Caren White on November 11, 2013:

Great hub! glad to hear that there are so many options.

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