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Product Info
How to Use
Customer Reviews
Product Info
What is Sentinel?

Sentinel is the only monthly oral preventive that guards against heartworms, adult roundworms, adult hookworms, whipworms, and prevents the development of flea eggs. Sentinel requires a prescription from your veterinarian.



  • Comes in palatable flavored tabs
  • Easy to administer just once a month
How it Works:

Milbemycin oxime eliminates the tissue stage of heartworm larvae and the adult stage of hookworm, roundworm, and whipworm infestations. Lufenuron, the other active ingredient, is an insect development inhibitor that breaks the flea life cycle by inhibiting egg development. Lufenuron prevents most flea eggs from hatching or maturing into adults and thus prevents and controls flea populations by breaking the life cycle. Sentinel may be given along with Capstar, which treats flea infestation.


Side effects are rare, though some animals may exhibit depression, drowsiness, vomiting, itching, hives, loss of appetite, diarrhea, or seizures. If these or other symptoms develop contact your veterinarian. It's important to maintain good personal hygiene, since humans can contract hookworms and roundworms. It's also important to eliminate fleas and to not feed your pet uncooked meat or fish. To prevent re-infection, clean up stools on a daily basis. Consult your veterinarian for pregnant or lactating dogs.

Brand Name:

Sentinel (Novartis)

Generic Name:

Milbemycin Oxime (mil-beh-my-sin ox-eem) and Lufenuron (lew-fen-your-on)

What is Sentinel:

Sentinel is given once a month for the prevention of heartworm disease in dogs. Sentinel also protects against hookworms, roundworms, and whipworms. Sentinel is also used to control fleas by preventing the development of flea eggs. Sentinel does not kill adult fleas. The American Heartworm Society recommends that heartworm prevention be used year-round. Sentinel may also be used for purposes other than those listed in this guide.

What should I discuss with my veterinarian before giving Sentinel to my pet:

Tell your veterinarian if your pet has ever had an allergic reaction to the medication.

What is the most important information I should know about Sentinel:

Sentinel is a prescription medication FDA-approved for use in dogs. Sentinel is available as artificial beef flavored (derived from pork and soy protein) chewable tablets. This medication should be given once a month year-round.

How should this medication be given:

Give Sentinel exactly as directed by the veterinarian. If you do not understand the directions ask your pharmacist or veterinarian to explain them to you. The usual dose of Sentinel for dogs 2 to 10 pounds is 2.3mg/46mg, 11 to 25 pounds is 5.75mg/115mg, 26 to 50 pounds is 11.5mg/230mg and 51 to 100 pounds is 23mg/460mg given once a month year-round. For dogs over 100 pounds give the appropriate combination of tablets. Heartworm testing should be performed prior to the start of prevention therapy. If your pet is off Sentinel for 6 months or less, re-start the medication and test after 6 months since microfilaria, that take 6 months to mature, will result in a positive test result. Store Sentinel at room temperature. Do not remove the tablet from its wrapper until ready to give the medicine. Keep this medication away from children and pets. Consult your veterinarian for pregnant or lactating dogs.

What happens if I miss giving a dose:

Give the missed dose as soon as you remember. Do not give a double dose of the medication.

What should I avoid while giving Sentinel to my pet:

Because humans can contract hookworms and roundworms from animals, it is important to maintain good personal hygiene. It is also important to eliminate fleas on your pet and in the household and to not feed your pet rodents or uncooked meat or fish. To prevent reinfection, daily cleanup of stools is recommended.

What are the possible side effects of Sentinel:

Side effects of Sentinel are rare although some animals may exhibit depression, drowsiness, vomiting, itching, hives, loss of appetite, diarrhea, hypersalivation, seizures, and weakness. If these or other symptoms develop contact your veterinarian.

What other drugs will affect Sentinel:

While Sentinel is safe to use in dogs at risk for MDRI-allele mutation (Australian Shepherds, Collies, Shelties, etc.), unless tested normal, caution is advised if your pet is also being given amiodarone (Cordarone), azole antifungals such as ketoconazole, carvedilol (Coreg), cyclosporine (Atopica), diltiazem (Cardizem), erythromycin (Ery-Tabs) or clarithromycin (Biaxin), quinidine, spironolactone (Aldactone), tamoxifen, and verapamil (Calan). Do not give Sentinel to your pet if already giving an alternate heartworm medication.

How to Use
  • Give Sentinel Flavor Tabs once a month on the same day of each month year-round.
  • Sentinel Flavor Tabs is for use in dogs only. Do not give to cats.
  • Watch your dog closely following dosing to be sure the entire dose has been swallowed. If it is not completely swallowed, give one more full recommended dose as soon as possible.

Do not remove Sentinel from its wrapper until ready to give to your pet.

Dogs/puppies: (4 weeks of age or older)
2-10 lbs
Give 1 Flavor Tab every month (Brown Box)
11-25 lbs
Give 1 Flavor Tab every month (Green Box)
26-50 lbs
Give 1 Flavor Tab every month (Yellow Box)
51-100 lbs
Give 1 Flavor Tab every month (White Box)
Over 100 lbs
Give combination of Flavor Tabs based on weight
Do not use!
Do not use!

Should be stored at room temperature between 59° and 77° F.

Sentinel Brown for Dogs 2-10 lbs:
Active Ingredient (per tablet)
Milbemycin Oxime
2.3 mg
46 mg
Sentinel Green for Dogs 11-25 lbs:
Active Ingredient (per tablet)
Milbemycin Oxime
5.75 mg
115 mg
Sentinel Yellow for Dogs 26-50 lbs:
Active Ingredient (per tablet)
Milbemycin Oxime
11.5 mg
230 mg
Sentinel White for Dogs 51-100 lbs:
Active Ingredient (per tablet)
Milbemycin Oxime
23 mg
460 mg
Customer Reviews
Sentinel is rated 4.432190760059613 out of 5 by 671.
Rated 5 out of 5 by from Works great! i have been giving this to my dogs for many years mainly for the flea prevention. We never have to worry about fleas. During a rough season we might see a flea on them but nothing becomes of it. It works. I have been concerned about whether is is healthy for my dogs, but I see the other options for flea control causing all kinds of health issues and seizurs and not controlling the fleas. ie like the drops, shampoos, sprays and collars. Those options can poison not only the animal but anyone that touches them.
Date published: 2016-07-21
Rated 5 out of 5 by from Glad I can still buy Sentinel! Lola is our 4th dog and it is so easy to give her the Sentinel once a month! It's a 2 in 1 that has been working for our home for over 20 years. We had a flea infestation once and I never want to go thru that again, so I order Sentinel from 1-800-Pet Meds since our vet no longer carries it.
Date published: 2016-07-18
Rated 5 out of 5 by from Great Product! Both my dogs Riley Ann and Shelby Quinn are taking the Sentinel monthly. They have been on it for years and it works amazing! Very happy with this product and the fact that it comes in flavor tabs. Also, 1-800 Pet Meds saved me a lot of money compared to what I was previously pay through my vet.
Date published: 2016-06-30
Rated 4 out of 5 by from Easy on the stomach My pomchi has a very irritable stomach when it comes to anything including water. I've tried many flea treatments including the topical (which he had a horrible seizure like reaction to) and a few different oral options all of which made him lethargic and vimit for a few days, while other options visably killed fleas within hours. This worked within 24 hours and provided no side effects that I noticed. While flea treatment was the #1 reason for this product I'm glad it did so without the harsh side effects some faster acting products had as my pets comfort and safety is most important. Peter is flea and symptom free after using sentinel !!
Date published: 2016-06-25
Rated 5 out of 5 by from A happy customer for over 20 years! I was lucky enough to have a Collie that lived to the ripe old age of 18 who used only Sentinel since his Vet warned against the slight possibility of problems with the breed on other products. I've followed his advice with my Sheltie whose getting ready to celebrate his 11th birthday without any problems. The product works and takes away any risks for those of use who love Collie breeds!!
Date published: 2016-06-21
Rated 5 out of 5 by from Great Product We have always kept our Shihtzus on Sentinel and it works great. Our Vet does not carry it anymore so we are so happy we can get it on 1800 PetMeds. The price is great and they ship fast. And so nice to get the discounts. Highly recommend.
Date published: 2016-06-15
Rated 2 out of 5 by from This product has changed My dogs have used Sentinel for years, this is the first year I have had fleas on all 3 dogs. My Son also has noticed fleas on his dogs. Not worth the mess going to try something else. Also, this product does not keep ticks off.
Date published: 2016-06-13
Rated 1 out of 5 by from This stuff sucks for fleas All of our dogs have been on this for 2 months now. They have not been heart worm tested since they started it so I can not say if it works for that. However, i can say that it does NOT work for fleas! All 4 of our dogs are infested with fleas! About a month ago we moved into a new house and ever since the dogs have been covered in fleas! Even if the yard is infested if this stuff worked like it was supposed to the dogs would not have fleas!! very disappointed that we bought a year worth for all the dogs! :(
Date published: 2016-06-01
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Do I also have to use a topical treatment for fleas/ticks?  Or does this do it all?

Asked by: TaraB
Sentinel only "sterilizes" the fleas to help break one of the four life cycles involved with treating and controlling an infestation. The ingredients in Sentinel alone will not kill adult fleas it only inhibits the development of flea eggs.
Answered by: Pharmacy Manager
Date published: 2016-03-12

How do get this

Asked by: Belinda
Place an order online or by calling 1800-738-6337. We will ask for your pet's name and veterinarian's information and contact them for your pet's prescription.
Answered by: Laura PetMed Pro
Date published: 2016-03-08

I purchased the 2-10 pounds tablets for my puppy and right now he weighs 9 pounds and is still growing. Once he passes 10 pounds it is okay to still give him the 2-10 pounds tablet?

Asked by: cmuhina
To ensure your pet is fully protected, you will need to administer Sentinel 11-25 lbs when your pet exceeds 10 pounds.
Answered by: Lisa M
Date published: 2016-03-04

Why do you have to give every month of the year when mosquitoes in our neck of the woods are not around in the winter months?

Asked by: becky
This medicine also prevents whip worm which lives in the soil for up to 5 years even in the winter time.all your dog has to do is walk across infected soil then lick his/her paws then they have whip worm.its better to use this as a precautionary measure than loose his/her life to a parasite
Answered by: deoge
Date published: 2016-01-18

Overdose ?????

A visiting small dog, approx. 11.5 lbs, ate one pill of my dogs Sentinel 51-100 lb. dose. Please tell me I haven't killed the little "princess" or i will never hear the end of it. The little dog is a Dachshund, Miniature. It passes for a dog, but just barely.
Asked by: Louise II
I know the product has been tested by the manufacturer at high doses, but you will need to look at the insert to see exactly how high the dose has been given safely. You can also try calling the manufacturer. There might be contact information on the packaging..
Answered by: SuzyCVT
Date published: 2016-01-13

I had to put my little molly down and I have a 6 month supply of the green sentinel left. Can I give this to my 70-75 lb dog and if so how much?

Asked by: Rose
You will need to give 4 Green Sentinel (11-25 pound dose) tablets a month to equal the proper dose for your 70-75 pound dog.
Answered by: SuzyCVT
Date published: 2015-12-02

If I have two dogs, both weighing 8 lbs each, can i just buy the one for 11-20 lbs dogs and cut the pill in half, giving them each a piece.

I notice that the dosage is doubled for the 11-20 as compared to the smaller dogs, so it seem that I should be able to cut it in half and administer half of the pill to each of the 8 lb dogs.
Asked by: Ajani
Because the tablets are not scored and the active ingredients are mixed with a flavor base, you cannot be sure that the active ingredients are mixed evenly in the tablet. As a result, you may be giving one dog a higher dose and the other dog a lower dose by splitting the tablet in half.
Answered by: SuzyCVT
Date published: 2015-11-21


My dog weighs 10 1/2 lbs. . Should I use the up to ten lbs or go to the eleven to the next higher for his Mede?
Asked by: NancyJ
Hello Anonymous! I believe that for Sentinel to work correctly go with the 11-25lbs - lime green box. This will assure that your pet receives the proper dose. You want to keep those cuddies off your pet!! Hope my answer has assisted with your decision. Mushu's mom
Answered by: Mushu's mom
Date published: 2015-11-01
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