Written By hannah hollinger
Published: 08/07/2020Updated: 08/30/2021
Sentinel for Dogs | Wag!

SentinelĀ® is a name-brand medication used to treat a range of parasitic infections in dogs, including fleas, roundworms, heartworms, hookworms, and whipworms. Sentinel contains lufenuron and milbemycin oxime, which are commonly used to treat parasites in small animals.

While SentinelĀ® is available as an over-the-counter medication, you should consult your vet before giving your dog this drug. Complications can occur due to SentinelĀ® as a result of allergic reactions and adverse side effects. Read on to find out more about the impact of SentinelĀ® on dogs.


SentinelĀ® is available as a flavored tablet that should be administered once a month, during or after a meal. The recommended dosage is 0.23 mg/lb of milbemycin oxime and 4.55 mg/lb of lufenuron. You should let your vet know if you plan on giving your dog SentinelĀ®, as it may interfere with other medications your dog is taking.


SentinelĀ® is highly effective at killing parasites like fleas, roundworms, hookworms, and heartworms. Lufenuron stops fleas from growing, effectively killing all eggs. However, lufenuron will not kill adult fleas. Meanwhile, milbemycin oxime works in different ways depending on the type of parasite. Milbemycin oxime kills adult hookworms, roundworms, and whipworms. It also eradicates heartworm larvae.Ā 

As a result, it can take several months for SentinelĀ® to eradicate a parasite, which is why it is essential to continue treatment monthly. If possible, you should start treatment a few weeks before flea or mosquito season.

Side effects

Side effects related to the use of lufenuron are rare but can occur. Side effects include:

Side associated with milbemycin oxime are more common and tend to be associated with overdoses. Side effects include:

As SentinelĀ® contains both of these drugs as active ingredients, any of these side effects are possible. If your dog has severe side effects resulting from taking SentinelĀ®, contact your vet immediately.Ā 


Drug interactions

At the time of writing, there are no drug interactions associated with taking SentinelĀ®. However, you should always inform your vet if your dog is currently taking a different form of parasite treatment. Also, let your vet know if you are giving your dog any vitamins, supplements, or prescription medications, as they may affect their treatment.

Allergic reactions and sensitivity

There are a few things to consider before giving your dog SentinelĀ®. SentinelĀ® is not suitable for dogs under 6 weeks old. You also shouldn't give SentinelĀ® to a dog that has recently tested positive for heartworm or hasn't been tested.Ā 

If your dog has a genetic mutation known as MDR1, they may be more sensitive to milbemycin oxime than other dogs. This mutation is more common in some breeds, including Collies and Sheepdogs. However, this mutation only causes adverse side effects when administering high quantities of milbemycin.

Frequently asked questions

What should I do if I forget to give my dog a dose of SentinelĀ®?

You should give your dog SentinelĀ® once every month. If you forget to give a dose, wait a month after you remember to give your dog their medication. Do not double up on doses or give your dog SentinelĀ® sooner. If you are using SentinelĀ® to prevent heartworm and haven't given your dog a dose in two months, contact your vet.

Can I use other parasite-preventing medication in conjunction with SentinelĀ®?

Many parasite medications contain similar active ingredients to SentinelĀ® and therefore shouldn't be used at the same time. However, some medications like CapstarĀ® can help speed up the treatment of fleas and other parasites. If you are using a medication with different ingredients, contact your vet to see if it is safe and if there are any considerations.

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Ā© 2024 Wag Labs, Inc. All rights reserved.