I decided to write a blog post answering some of the common questions I hear about Sentinel flea control medication for dogs. Sentinel is different from most other types of flea control products because it comes in the form of a pill rather than a liquid topical that is applied to your dog’s skin. The active ingredients in Sentinel, milbemycin oxime and lufenuron, are absorbed by your dog systemically and remain in the bloodstream for a period of around 30 days. Sentinel tablets should be given with a meal to ensure adequate absorption.
Sentinel for dogs is a chewable, beef-flavored tablet given once every 30 days to prevent heartworm infection as well as flea infestations. It can be given to dogs and puppies as long as they are older than 4 weeks and weigh more than 2 pounds. Studies showed no ill effects on puppies whose mother was given three times the normal dose of Sentinel while nursing and pregnant. However, you should consult with your veterinarian on whether or not giving Sentinel to pregnant or nursing dogs is recommended.
So, how does Sentinel work? Milbemycin oxime is the ingredient in Sentinel that prevents heartworm disease. You may have also heard of a product called Interceptor. The main ingredient in Interceptor is milbemycin oxime. The only thing that makes Sentinel different from Interceptor is that is also contains lufenuron, the ingredient used to control flea populations.
In addition, milbemycin oxime also aids in the prevention of infection against many intestinal parasites including hookworms, roundworms, and whipworms. Because of this additional protection against intestinal parasites many veterinarians recommend giving Interceptor or Sentinel to dogs year-round even though mosquitoes don’t pose a threat during certain cold months of the year. If you’re really into pharmacology, milbemycin oxime is classified as a macrocyclic anthelmintic. What this means is that it kills worms by interfering with their life cycle. The proper does for dogs is approximately 0.23 mg per pound of body weight.
Lufenuron is an insect development inhibitor. It prevents flea reproduction. Bascially, lufenuron is birth control medication for fleas. However, like birth control medication for people, it doesn’t kill the adult flea. When a female flea ingests a blood meal from a dog that has lufenuron running through his system, she gets her own small dose of lufenuron. This is deposited in her eggs which are unable to develop, mature, or hatch into adults. Sad for the fleas, but good for you and your dog. The proper dose of lufenuron is 4.55 mg per pound.
You may have heard of a product called Program. Program contains one single ingredient, lufenuron, and is used to prevent flea infestations. So if you’ve been paying attention, you’ve probably figured out by that Sentinel is simply the combination of two products, Program and Interceptor. It comes in four different sizes depending on the weight of your dog.
Brown 2 to 10 pounds
Green 11 to 25 pounds
Yellow 26 to 50 pounds
White 51 to 100 pounds
Dogs over 100 pounds will need to take two tablets of the appropriate size.
Now that you have the basics down, let’s start answering some questions:
1. Does Sentinel kill fleas?
No. Sentinel flavor tabs do not kill adult fleas. It prevents adult fleas from reproducing. So, if your dog picks up a flea or two at the dog park or during a walk, those fleas will be unable to reproduce. One of the things that makes dealing with fleas so frustrating is their ability to reproduce so quickly. Sentinel is a great product to use if your dog currently doesn’t have fleas and you’d like to keep it that way. Even if he does happen to pick up a flea or two, the problem will be a lot easier to handle.
And if you discover yourself with a big flea problem, Sentinel can also make life easier for you and your dog. The caveat is that you’ll need to use another product in combination with Sentinel to kill the adult fleas. Something like Frontline Plus or Capstar are good choices. Between the two I would probably choose Capstar, mostly because of its ability to work so quickly. Capstar contains an ingredient called nitenpyram which begins to work in 30 minutes. Within a period of 4-6 hours, 99% of adult fleas on your dog will be dead. However, Capstar only lasts for 24 hours so you’ll probably want to give one tablet to your dog every 3-4 days until adult fleas are no longer observed.
2. I gave my dog Sentinel but he still got fleas. What gives?
Sentinel flea medication doesn’t create an invisible force-field around your dog that magically repels fleas when they reach a certain distance. That would be like someone complaining that they got into a car accident even though they had their seat belt on. Fleas and accidents are still a part of the environment. If your dog comes into contact with other animals that have fleas or visits a flea-infested area, he may very well get fleas. However, these fleas will be unable to reproduce. If you’re worried, you can use another product like Capstar or Frontline until you no longer see adult fleas.
The bottom line is: if you see still fleas on your dog or puppy after giving Sentinel he is getting re-infected either from your house or his environment.
3. Does the flea have to bite my dog in order for Sentinel to work?
Yes. Sentinel is absorbed into the bloodstream. If your dog suffers from flea allergy dermatitis (an allergic skin reaction that occurs from flea bites) you should probably use a topical product like Frontline Plus for flea control. Revolution is a topical heartworm and flea control product but the medication is also absorbed into the bloodstream so that’s probably not a good choice either.
4. Can you get Sentinel for dogs without a prescription?
No. Because Sentinel flea control medication also contains milbemycin oxime, a heartworm preventative, you need to get a prescription from your veterinarian. Your dog will need to have a negative heartworm test before taking Sentinel. Reactions such as labored respiration, vomiting, salivation, and lethargy have occurred in heartworm positive dogs that have been given milbemycin oxime. These reactions are caused by the death and release of microfilariae (baby heartworms) living in the bloodstream.
5. Are there any side effects to be aware of?
As with any drug in human and veterinary medicine there is always the risk of side effects. The following adverse reactions have been reported in dogs after giving milbemycin oxime or lufenuron: vomiting, depression, lethargy, itchiness, hives, diarrhea, weight loss, poor coordination, seizures, hypersalivation, and weakness.
If any of these reactions occurred in our patients during my ten years working in veterinary medicine I haven’t been made aware of them. The only experience I have is one owner whose Basset Hound vomited up his Interceptor tablet after the first time they gave it when he was a puppy. However, we think the problem stemmed from an unsavory snack she stole from the garbage a short time before. She has not had an issue with the medication since.
If you’re concerned about the safety of Sentinel or think your dog may be experiencing a side effect from the medication you should contact your veterinarian.
6. Does Sentinel protect against ticks?
No. If your dog has a high risk of tick exposure you might want to consider using a product such as Frontline Plus or Revolution.
7. Does Sentinel kill tapeworms?
No. Even though Sentinel controls most of the intestinal parasites that dogs are susceptible to, it does not kill tapeworms. Dogs acquire tapeworms by either ingesting fleas (usually while biting at them) or ingesting an animal (rabbit, mouse, etc.) that has fleas. So, if your dog is infected with tapeworms flea control should definitely be a part of your veterinarian’s treatment plan. As far as I know, the only medication that kills tapeworms effectively is praziquantel which can be found in products such as Droncit, Drontal, and Drontal Plus. Don’t waste your money on over-the-counter worming medications since these medications only target certain stages of the worm’s life cycle and are ineffective. Praziquantel is the medication you need and it can only be purchased with a prescription.
In an indirect sort of way Sentinel may prevent tapeworm infection by decreasing the flea population but the active ingredients themselves do not physically affect tapeworms at all.
8. It seems strange that Sentinel doesn’t kill fleas. Can’t I just use Frontline Plus instead which kills adult fleas and prevents them from reproducing?
Yes, you can certainly choose to use Frontline Plus for flea control and a separate heartworm preventative such as Interceptor or Heartgard instead of Sentinel. However, many pet owners like the added convenience that Sentinel offers. Instead of dealing with two different products you only have to worry about one. It can be hard to remember what days to give the heartworm preventative and on top of that, you also have to keep track of when another dose of flea control is needed. Plus, if you’re dealing with an active flea infestation, you need to apply a dose of Frontline once every 30 days for 3 days to break the cycle. You might as well spend that money on Sentinel and a couple doses of Capstar!
Personally, I would rather give my dogs one pill monthly and be done with it. I usually find a flea or two on my dogs at least once during the summer months since they get to run around on our 3 acre property. However, because I know they’ve been getting Sentinel all along, I don’t sweat it. I usually just sqwish the fleas I find and that’s the last I see of them. I’ve never had to give them anything other than Sentinel. Although, if I did continue to see fleas I would give them Capstar once every 3-4 days until the fleas were gone. To me, giving a tablet is much easier than dealing with the liquid tubes, and the greasy mess associated with topical flea medications. But you should do whatever is most comfortable for you.
9. Sentinel seems expensive. Isn’t there a cheaper alternative?
It seems like a lot of people are on the lookout for cheap Sentinel flavor tabs for dogs. If you think about it though, what Sentinel costs you in dollars it makes up for by saving you time. Have you ever had to deal with a severe flea infestation? With “traditional” flea control products such as flea shampoos, flea dips, flea bombs, etc. you’re going to be investing an awful lot of time. Most of these products only target the adult stage so 30 days later you have to start all over when the larvae and pupae living in your dog’s environment develop and hatch into adult fleas. You have the vacuuming, the dipping, the combing . . . Ugh! It’s a vicious cycle than can easily drive a person bonkers. Over the counter flea products are both less effective and more dangerous to your dog. Sentinel is expensive, but remember–it contains both a heartworm preventative and a flea control product in one tablet.
Well, I hope that covers most of the questions you had about Sentinel flea control medication for dogs. I know some people who don’t care much for the product mostly because it doesn’t kill adult fleas. However, I don’t think that’s such a big problem as long as you’re prepared for the fact that you still might find fleas on your dog. However, if you do, it will only be temporary. I think a lot of people who complain about Sentinel are those that weren’t aware before buying the product that it doesn’t kill adult fleas on contact. It’s what I’ve been giving my dogs for the past few years, and I’ve been very happy with the results.
If you have any additional questions which I didn’t address, please leave them in the comments below. Thanks!
References: Sentinel Product Insert NADA #141-084 Approved by the FDA