Credelio vs Comfortis

When it comes to flea and tick prevention for our pets, we want the best. Two products that have gained attention in recent years are Credelio and Comfortis. While both have their merits, pet owners may wonder: which one is better? This article delves deep into both products, comparing their efficacy, side effects, and cost.

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Frequently Asked Questions

1. What Are Credelio and Comfortis?

Credelio: Manufactured by Elanco, Credelio is an oral treatment for fleas and ticks. The active ingredient, Lotilaner, is part of the isoxazoline class and works to paralyze and kill fleas and ticks upon ingestion.

Comfortis: A product of Elanco, Comfortis is an oral flea treatment for dogs and cats. Spinosad is its active component which effectively disrupts the nervous system of fleas, leading to their death.

2. Efficacy: Which One Acts Faster?

While both products are known for their fast action:

  • Credelio starts killing fleas within 4 hours and ticks within 8 hours.
  • Comfortis begins its flea-killing action within 30 minutes and achieves 100% efficacy in 4 hours.

3. Duration: How Long Do They Last?

Both medications are designed to be administered monthly:

  • Credelio offers protection against fleas and ticks for a full month.
  • Comfortis protects against fleas for 30 days but does not offer tick protection.

4. Side Effects: What Are the Risks?

Like all medications, both Credelio and Comfortis have potential side effects:

  • Credelio: Some reported side effects include weight loss, elevated blood urea nitrogen (BUN), excessive thirst, and diarrhea.
  • Comfortis: The potential side effects include vomiting, lack of appetite, lethargy, and itchiness.

5. Pricing: Which Is More Economical?

Prices may vary based on location and vendor. Generally:

  • Credelio is in a similar price range as Comfortis but offers the added advantage of tick protection.
  • Comfortis might be slightly cheaper in some areas but doesn’t provide tick protection.

6. Special Considerations

For Cats: Comfortis is available for both dogs and cats. Credelio, while primarily for dogs, also has a formulation for cats.

Discontinuation Rumors: There have been speculations about Comfortis being discontinued, but as of now, it’s still available in many markets.

7. The Verdict: Which One Is Better?

The “best” choice often depends on individual pet needs and owner preferences:

  • For those seeking both flea and tick protection, Credelio might be more suitable.
  • If only flea protection is a priority and the cost is a concern, Comfortis could be the go-to option.

Frequently Asked Questions

Q: Can I administer Credelio and Comfortis simultaneously?

A: Combining different flea and tick medications isn’t typically recommended, as it can increase the potential for adverse reactions. Always seek advice from a veterinarian before combining treatments.

Q: Are there specific weight requirements for administering Credelio or Comfortis?

A: Yes, both products have weight classifications that dictate dosages. Ensure you choose the right dosage for your pet’s weight to ensure efficacy and safety.

Q: How do Credelio and Comfortis work internally in the pet’s system?


  • Credelio uses its active ingredient, Lotilaner, which targets the nervous system of fleas and ticks. Once ingested, it results in paralysis and eventual death of these pests.
  • Comfortis utilizes Spinosad, which excites the nervous system of fleas, leading to muscle contractions and paralysis before death.

Q: Are there any dietary requirements when administering these medications?

A: While Credelio doesn’t have strict dietary requirements, it’s more effective when given with food. Comfortis should be administered with a meal for optimum absorption.

Q: How quickly can I bathe my pet after giving them the medication?

A: Since both Credelio and Comfortis are oral treatments, they won’t wash off with water or shampoo. You can bathe your pet at any time without affecting the efficacy of these treatments.

Q: Are there breed-specific reactions to be aware of?

A: While no breed-specific reactions are listed for Credelio, some dog breeds (like collies) with a genetic mutation may be more sensitive to Comfortis. Always discuss breed-specific concerns with a vet.

Q: My pet vomited shortly after taking the medication. What should I do?

A: If your pet vomits within an hour of administration, the dose may not have been fully absorbed. Consult your vet for guidance on whether a re-dose is necessary.

Q: Are these medications safe for pregnant or lactating pets?

A: Safety studies haven’t conclusively determined the effects on pregnant or lactating pets. Before administering to a pregnant or nursing pet, it’s imperative to consult with a veterinarian.

Q: Will these medications protect against heartworms or other parasites?

A: While Comfortis is solely a flea treatment, Credelio targets fleas and ticks. Neither product is designed to protect against heartworms or other internal parasites. If heartworm prevention is a concern, consider products like Trifexis.

Q: Can I switch between Credelio and Comfortis without a waiting period?

A: Generally, there isn’t a mandatory waiting period between switching products. However, for optimal protection and to monitor for potential side effects, it’s recommended to consult with a vet before making any switches.

Q: How do I store Credelio and Comfortis medications?

A: Both medications should be stored in their original packaging at room temperature. Avoid exposure to direct sunlight or excessive moisture to maintain their efficacy.

Q: Are there any age restrictions for starting my pet on Credelio or Comfortis?


  • Credelio: Suitable for puppies 8 weeks of age and older, weighing at least 4.4 pounds.
  • Comfortis: Safe for puppies and kittens 14 weeks of age and older.

Always double-check with your vet when starting young pets on medication.

Q: Can I administer these treatments to other animals, like ferrets or rabbits?

A: Both Credelio and Comfortis are designed specifically for dogs and cats. Using them on other animals may pose risks. Always consult a veterinarian when considering treatments for non-target species.

Q: How long does it take for fleas to die after administering the treatment?


  • Credelio: Begins killing fleas within 4 hours.
  • Comfortis: Starts killing fleas in just 30 minutes, with 100% efficacy in 4 hours.

Q: Can I use other flea/tick prevention methods like collars or shampoos with these medications?

A: Combining treatments might increase the risk of over-medication and potential side effects. It’s advisable to discuss any additional treatments with your vet to ensure safety.

Q: Are there known long-term side effects with prolonged use of Credelio or Comfortis?

A: No long-term adverse effects have been identified in dogs and cats with the continuous monthly administration of either medication. However, monitoring your pet for any unusual behavior or side effects is always prudent.

Q: Is there a risk of resistance building up in fleas or ticks to these medications?

A: To date, there’s no widespread evidence to suggest fleas or ticks are developing resistance to Credelio or Comfortis. Still, as with all insecticides, there’s always a potential risk. Regular and consistent treatment is key to effective control.

Q: Can I give half doses if my pet is in between weight categories?

A: It’s not advisable to split or modify doses without consulting a veterinarian. Proper dosing ensures maximum effectiveness and safety.

Q: What should I do if I miss a monthly dose?

A: Administer the missed dose as soon as you remember and resume the monthly schedule. If there’s a significant lapse, consult with your vet about re-establishing protection.

Q: Are there any contraindications for using Credelio or Comfortis with other medications?

A: There haven’t been any widespread contraindications reported. However, always notify your vet of any other medications your pet is on before administering a new one.

Q: Are there breed-specific reactions to Credelio or Comfortis that pet owners should be aware of?

A: While both medications are generally safe across breeds, some pets may react differently due to genetic predispositions. It’s crucial to monitor any breed for potential adverse reactions and report any unusual symptoms to the vet immediately.

Q: Can pregnant or lactating pets use Credelio or Comfortis?


  • Credelio: The safety in breeding, pregnant, or lactating dogs has not been evaluated.
  • Comfortis: It’s approved for use in breeding, pregnant, and lactating dogs and cats. However, always consult your veterinarian before administering any medication to pregnant or nursing pets.

Q: What steps should I take if I believe my pet is having an adverse reaction to the treatment?

A: Discontinue use immediately and seek veterinary attention. Document the symptoms and provide any relevant details, such as the batch number of the medication, to assist in the diagnosis.

Q: Can I administer Credelio or Comfortis if my pet has a history of seizures or neurological issues?

A: While rare, both medications have reports of causing or exacerbating seizures in susceptible animals. It’s essential to provide your veterinarian with a full medical history to determine the best treatment option.

Q: If my pet spits out the pill or vomits shortly after taking it, should I give another dose?

A: If the pill isn’t swallowed or if your pet vomits within an hour of administration, it’s advisable to give another full dose to ensure efficacy. However, if you’re uncertain, contact your vet for guidance.

Q: How do Credelio and Comfortis impact the environment once excreted by the pet?

A: The environmental impact is minimal, as the active ingredients break down quickly. Still, always pick up and dispose of your pet’s waste to minimize any potential ecological effect.

Q: Can I switch between Credelio and Comfortis without a break or overlap?

A: Ideally, when transitioning between treatments, there shouldn’t be a gap to ensure continuous protection. However, always consult with a vet to plan a safe transition.

Q: Are there any interactions with common over-the-counter medications or supplements?

A: No widespread interactions between Credelio, Comfortis, and common OTC supplements or medications have been reported. Nonetheless, always keep your vet informed about all treatments your pet receives.

Q: How do these medications affect parasites internally, like heartworm or intestinal worms?

A: Comfortis primarily targets fleas, while Credelio targets both fleas and ticks. They don’t directly address internal parasites. If you’re concerned about internal parasites, consider products like Trifexis (which combines the properties of Comfortis with heartworm prevention) and always maintain a regular deworming schedule.

Q: Is there any risk of these medications impacting the household, especially with young children?

A: Since Credelio and Comfortis are oral treatments, there’s no residue left on the pet’s coat, reducing the risk of exposure to humans. As with any medication, keep it out of reach of children and ensure they wash their hands after handling pets to maintain general hygiene.

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