More Questions About Sentinel Flea and Heartworm Medication for Dogs

I’ve received quite a few more questions about Sentinel for dogs so I thought I would address these in another post. A lot of people seem to be confused about what other medications can be given along with Sentinel as well as the fact that Sentinel is both a heartworm and a flea medication. Also, it’s important to remind everyone that even though Sentinel prevents flea reproduction, it does not kill adult fleas! 🙂

If I don’t address your question or concern below please leave me a note in the comments section below. Also, you might find the information you need in my earlier post about Sentinel.

1. Does My Dog Really Need a Heartworm Test Before Giving Sentinel?

The active ingredient in Sentinel for the prevention of heartworm infection is milbemycin oxime. Milbemycin oxime works a little differently than other ivermectin-based heartworm products including Heartgard and Heartgard Plus. If milbemycin oxime is given to a heartworm-positive dog, the microfilariae are killed much faster than with the ivermectin products. This puts the dog at greater risk for a shock-like reaction if many larvae die at once. Of course, a heavily infected dog will be more at risk than a dog with a light infection.

For liability and safety reasons, veterinarians are required to use medications according to their labeled instructions. The Sentinel product insert states:

Prior to administration of Sentinel Flavor Tabs, dogs should be tested for existing heartworm infections. Infected dogs should be treated to remove adult heartworms and microfilariae prior to intitiating treatment with Sentinel Flavor Tabs. Mild, transient hypersensitivity reactions manifested as labored respiration, vomiting, salivation and lethargy have been noted in some treated dogs carrying a high number of circulating microfilariae. These reactions are presumably caused by release of protein from dead or dying microfilariae.

If you do not wish to test your dog for heartworm infection prior to giving him Sentinel your veterinarian may or may not allow you to sign a medical waiver.

2. Can I Get Sentinel Flea Pills for Dogs Without a Prescription?

Because Sentinel is also a heartworm medication there is no way to get it without a prescription. However, if you only need the flea preventative, lufenuron, this can be purchased without a prescription from your veterinarian. You should look for a product called Program, which contains the medication lufenuron and nothing else. Remember that lufenuron only inhibits the development of flea eggs and does not kill adult fleas. If you find someone selling Sentinel without a prescription online it’s probably not worth buying.

3. What’s the Difference Between Interceptor and Sentinel for Dogs?

Interceptor only contains the active ingredient milbemycin oxime which is used as a preventative for heartworm infection as well as intestinal parasites such as roundworms, hookworms, and whipworms. Sentinel contains milbemycin oxime as well as an additional ingredient, lufenuron, which “sterilizes” fleas. Because it contains an additional medication, Sentinel is more expensive than Interceptor.

4. What ingredients does Sentinel contain?

As stated previously, there are two Sentinel ingredients: milbemycin oxime and lufenuron. Milbemycin oxime is used for the prevention of heartworm infection as well as the control of numerous intestinal parasites including roundworms, hookworms, and whipworms. Lufenuron inhibits the development of flea eggs.

5. How Does Sentinel Work?

You can find this information by reading the product insert:

Milbemycin oxime, one active ingredient in Sentinel Flavor Tabs, is a macrocyclic antihelmintic which is believed to act by interfering with invertebrate neurotransmission. Milbemycin oxime eliminates the tissue stage of heartworm larvae and the adult stage of hookworm (Ancylostoma caninum), roundworm (Toxocara canis and Toxocara leonina) and whipworm (Trichuris vulpis) infestations when adminstered orally according to the recommended dosage schedule.

Lufenuron, the other active ingredient in Sentinel Flavor Tabs, is an insect development inhibitor which breaks the flea life cycle by inhibiting egg development. Lufenuron’s mode of action is interference with chitin synthesis, polymerization and deposition. Lufenuron has no effect on the adult flea. After biting a lufenuron-treated dog, the female flea ingests a blood meal containing lufenuron which is subsequently deposited in her eggs. Lufenuron prevents most flea eggs from hatching or maturing into adults and thus prevents and controls flea populations by breaking the life cycle.

Some important information to note is that the active ingredients in Sentinel work systemically. That is, the ingredients are absorbed into the bloodstream. This means that in order for lufenuron to work, the fleas have to bite your dog. So, if you know your dog has flea allergies (flea allergy dermatitis) you might want to consider using a different flea control product.

6. Where Can I Find Cheap Sentinel For Dogs?

Because Sentinel Flavor Tabs for dogs contains both a heartworm preventative and a flea medication it costs more than other products. The best way to find the cheapest price on Sentinel is to simply search online for the best price you can find. However, I don’t recommend making your final purchase on the Internet.

What I would do is ask your veterinarian if they will match some of the cheaper prices you find online. They will probably need to see a current print-out of some of the websites you visit because these prices might vary from one week to the next. That way you know you’re getting the best and safest product by purchasing from your veterinarian directly. I think as more people demand lower prices veterinarians will follow suit. Of course, veterinarians have a lot more overhead than online retailers which accounts for the higher prices. Animal hospitals also offer better customer service and know more about the products than online retailers. You might also notice there’s a lot of variability in prices from one vet to the next. However, at the end of the day, I always think it’s better to support your local veterinarian whom you’ve established a relationship with, rather than some faceless entity you stumble upon online.

7. Can I Use Sentinel With Other Flea Control Products Like Frontline?

Yes. In fact, if you see adult fleas on your dog concurrent use of an adulticide like Frontline or Capstar is both recommended and encouraged to provide adequate flea control. Dogs that have repeated exposure to flea infested animals or environments will always have adult fleas if an adulticide is not used. An adulticide is a product that kills adult fleas.

I would probably use Capstar instead of Frontline though. Mainly because there seems to be a growing problem with owner compliance in terms of applying Frontline correctly. I think the dog is more likely to get the proper dose of medication if a pill is given instead of a topical product. When it comes to creating the most effective system for flea control, I think the concurrent use of Sentinel and Capstar gives you the greatest chance of success. The only downside to Capstar is that it only lasts for 24 hours.

The only product I would hesitate giving along with Sentinel is Revolution, or any other flea control product that also contains a heartworm medication. Although this extra dose of heartworm medication may not hurt your dog, you don’t want to give him more medication than he really needs. The manufacturer states that when the active ingredients in Sentinel were used with a variety of adulticides, vaccines, antibiotics, antehelmintics (dewormers), steroids, flea collars, shampoos, and dips, no adverse reactions or interactions were noted in dogs. If you’re concerned about using Sentinel with other medications or products you should contact your veterinarian for advice.

References:
Sentinel Product Insert
Preventing Heartworm Infection in Dogs (Chemoprophylaxis)
Veterinary Drug Handbook (Fourth Edition) by Donald C. Plumb