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My cat's flea treatment failed. What to do while waiting for new meds?

Updated on September 23rd, 2025

Pet's info: Cat | American Shorthair | Male | neutered | 2 years and 3 months old | 15 lbs

Hi, I gave my cat Hartz UltraGuard fleas and ticks. It didn’t work and fleas are growing in number. I was told that it is because my cat is large (15lbs) and also to stop Hartz because the treatment might be toxic. How long do I have to wait to give him advantage II for large cats? What can I do while I wait, since the fleas are still alive? Thank you!

4 Answers

Most Helpful Answer

Answered By Dr. Strydom, DVM

Veterinarian

Published on May 7th, 2020

If you want an effective product please use one of newer ones like Cheristin. I don't think you will get any better results with Advantage. It is recommended to wait a minimum of 3 weeks between product applications.

https://worldtails.securevetsource.com/itemView/view/198944_HomeDelivery.pml?productId=115569 While you wait you can get Capstar and give him that every couple days if need be. One pill lasts 24 hours but will kill everything on him.

https://www.petco.com/shop/en/petcostore/product/capstar-flea-tablets-for-cats-2-25-lbs You also need to treat the house or the fleas will keep getting on him. I recommend Knockout Spray ES:

https://www.chewy.com/virbac-knockout-es-area-treatment/dp/53856

4Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Dr. Melanie, BVSc MS
Veterinarian
Published on April 30th, 2019
Since it's been two weeks, it's fine to give the Advantage now. You can also give her Capstar. It's a one time pill that starts killing fleas in 30 minutes. You will also have to disinfect the environment. Wash her bedding in hot soapy water, and vacuum the furniture and carpet surfaces. You can use a spray to kill fleas in the house, such as Indorex, or a flea bomb would work well to kill the fleas in the home. I hope this helps!
1Pet Parents found this answer helpful
Answered By Dr. Melanie, BVSc MS
Veterinarian
Published on July 18th, 2019
Hartz is a pretty poor product, so I'm not surprised it didn't work. You have to wait 14 days before it's safe to apply the Advantage, so in two more days, you can do it. Keep giving Leon the Capstar until then. You will also have to disinfect the environment. Wash his bedding in hot soapy water, and vacuum the furniture and carpet surfaces. You can use a spray to kill fleas in the house, such as Indorex, or a flea bomb would work well to kill the fleas in the home. Best of luck.
1Pet Parents found this answer helpful
Answered By Dr. Melanie, BVSc MS
Veterinarian
Published on June 17th, 2019
You are right that Hartz is pretty awful, and it's good that you washed if off Repo. Keep an eye out for drooling, agitation, and even seizures. If you see those signs, have her seen by a vet right away. I can give you a safe flea treatment program for her, just wait a few days before doing it. First, I would give her Capstar. It's a one time pill that starts killing fleas within 30 minutes. Then follow up with a spot on treatment, such as Advantage or Revolution. This is a treatment that has to be used once a month. You will also have to disinfect the environment. Wash her bedding in hot soapy water, and vacuum the furniture and carpet surfaces. You can use a spray to kill fleas in the house, such as Indorex, or a flea bomb would work well to kill the fleas in the home. I hope this helps!
1Pet Parents found this answer helpful

Smart Picks for Smart Questions

Related Questions

My cat's flea treatment isn't working. Can I switch brands safely?

I would not use the Advantage so close to applying another treatment. Wait at least 3 weeks since previous treatment. It may still be killing the fleas on the cat, but if fleas are still in the environment, new ones are jumping onto the cats. I would recommend treating the environment to help get rid of fleas more effectively. It will take at least 4 months to get rid of fleas if you are treating ONLY the pets. Make sure all pets are treated as well. Here are some articles for more info. http://www.veterinarypartner.com/Content.plx?P=A

Updated on September 23rd, 2025

Health & Wellness

Why are fleas still on my cat and in my house after treatment?

If you haven't treated the house, that will be a continuing source of fleas. I would call an exterminator to kill the fleas. As for Chubbs, give him Capstar once a day for the next seven days. It's safe to give one pill daily, and starts killing fleas in 30 minutes. When it has been two weeks since you last applied the Advantage, you can apply another dose. I hope this helps!

Updated on September 23rd, 2025

Health & Wellness

My cat still has fleas after Advantage. What flea treatment can I use?

Thanks for using Petco Pet Education Center, formerly Petcoach! Yes, you may in about 5-6 days. However, I would highly recommend you use a stronger and likely more efficacious product. There are plenty of flea products in the market and a lot of them are very effective. I prefer Bravecto and Frontline plus. You can pick one of those products. The nice thing about Bravecto is that it is very effective and it is only applied once every 3 months. You can also use a product called Capstar along with one of the previously mentioned products which can help kill a lot of fleas at once. Remember to vacuum all the surfaces that have contact with your pup regularly. This is very likely going to work well. Good luck and have a great day!

Updated on September 23rd, 2025

Health & Wellness

My cat's flea medicine isn't working. Should I use a flea collar?

I'm sorry to hear you've had trouble finding an effective flea med! Most over-the-counter options are not very effective in my experience, including Advantage - although it's probably the best of the currently available OTC options! Flea collars do not work well, and can often be toxic to cats. Instead, I would recommend getting a prescription flea medication like Revolution or Bravecto from your veterinarian. This will be safe for your kitty, and much more effective. If it's been at least 1-2 weeks since you applied the Advantage, it should be safe to go ahead and use a new medication from your vet.

Updated on September 23rd, 2025

Health & Wellness

My cats still have fleas after treatment. What should I do next?

If you used a topical preventative and applied it soon after bathing, it won't have been as effective as it should be. These produce use the oils in the skin to spread. When you bathe a pet, these oils are stripped and you have to wait for them to build up again. Typically, it recommended to apply a topical 3 days before or 3 days after a bath or getting wet. It should then be used monthly for at least 3 consecutive months, preferably year round. You should also treat the environment, since most fleas live off of the pet and only hop on for feeding. Vacuum everywhere the cats have been. Discard of the bag or empty the canister outdoors immediately after. Wash all bedding in the hottest water allowable by fabric and dry in the dryer. Use a cat safe area treatment to prevent reinfestation. An oral preventative, such as CapStar, can be given to quickly kill any adult fleas on the cats. Get it from your vet or from the local Petco.

Updated on September 23rd, 2025

Health & Wellness

Fleas won't die! When can I re-treat my cats and bomb my home?

Hello. I would wait the full month before using any more topicals on your cats, so that would mean 10/19. If you want to try a Seresto Collar ( which works very well ), you could put this on today if you like. You can also purchase Capstar ( nitenpyram ) over the counter & administer this every 2-3 days until you can use another topical. If you prefer the topicals, consider using Bravecto for cats. I have been very happy with this for my cats & you just apply this once every 3 months. As for bombs, just see what your garden center carries. Most, if not all, now contain an IGR or insect growth regulator, so look for this as it extends the use of the product when it comes to killing fleas. Each product will recommend how many bombs to use based on the square footage of your home. Thanks for using Petco Pet Education Center, formerly Petcoach.

Updated on September 23rd, 2025

Health & Wellness

My cat still has fleas after vet treatment, what should I do?

Hello, my name is Dr. Shines and I am happy to help. Ugh! Fleas are the worst but the good news is that you can effectively get rid of them if you use a good product and are diligent in the treatment. Here is a link about the flea life cycle: https://vcahospitals.com/know-your-pet/flea-control-in-dogs The flea life cycle can last as long as 6 months. The key to getting rid of fleas is to make sure EVERY dog and cat in the house is treated with a good flea prevention AND that this treatment lasts an entire 6 months. Your vet can give you access to the best flea products on the market. top products for cats are Revolution and Cheristan. I recommend to ask your veterinarian what they used and to continue it for a solid 6 months. Also know you will likely continue to see fleas for at least 6 weeks (assuming your product is working correctly) because of the newly emerging adult fleas. Lastly, know there is great variation in the effectiveness of topical flea products. As far as they go, for over the counter options, name brand Frontline and Advantage are your best options (but what you get from the vet is usually newer and better). I hope this helps and please feel free to reach out with any additional questions.

Updated on September 23rd, 2025

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