Written By Mel Lee-Smith
Published: 09/11/2020Updated: 08/30/2021
Capstar for Dogs | Wag!

Capstar is an FDA-approved oral flea and tick medication made by Elanco that’s available over-the-counter at most major retailers. Nitenpyram, the primary ingredient in Capstar, is a neonicotinoid pesticide that shares many molecular properties with nicotine. Nitenpyram enters the canine’s bloodstream through the stomach wall. When the flea bites the dog, it ingests the poison, causing neurotoxicity and death. 

Nitenpyram interferes with invertebrates’ nervous systems by attaching to neurons and “exciting” them to the point of cell death. This neurological overstimulation is why you may see fleas spasming after you apply a flea treatment. 

Capstar only targets adult fleas and doesn’t eliminate eggs or larvae. This, along with its short-acting effects, is why it can be given more often than other flea preventatives. This medication may be given as frequently as once a day to break the reproductive cycle by killing fleas before they reach reproductive maturity.


Capstar tablets come in boxes of 6 tablets and are available in 2 strengths: 11.4 mg tablets for small dogs and 57 mg tablets for large dogs.

  • 2 to 20 lbs. — 1 small dog (11.4 mg) tablet 1-2 times per week

  • 26 to 125 lbs. — 1 large dog (57 mg) tablet 1-2 times per week

*One to two doses a week is the manufacturer’s recommendation, though the product label states this medication is safe up to once every 24 hours if reinfestation occurs. 

Dosage instructions

Capstar can be put inside a treat or pill pouch to encourage acceptance; this is usually the easiest approach for dogs that like treats. 

You can also administer Capstar directly into the dog’s mouth, but you must position the tablet at the very back of the tongue. Once in place, gently hold your dog’s muzzle so they can’t spit it out and softly massage the throat while blowing on their face to trigger the swallow reflex. 


A clinical study of 211 pet dogs and cats found that oral nitenpyram started killing fleas within 30 minutes of ingestion, and by hour 6 had killed more than 95% of fleas in the treatment group. 

Studies comparing Capstar to Frontline, Advantage, Revolution, and Cyflee found that Capstar works significantly faster and had a higher efficacy rate at the 3-hour mark than the other flea preventatives. 

Active ingredients in Capstar


Side effects

Aside from scratching, adverse reactions are atypical in treatment studies involving Capstar’s active ingredient. According to Capstar’s information pamphlet, possible side effects include:

  • Stomach upset

  • Watery stools

  • Hyperventilation

  • Seizures

  • Whining or barking

  • Drooling

  • Excitability

  • Lack of appetite 

  • Disorientation

  • Changes in mood or activity level

  • Rash

  • Anxiousness

  • Twitching

  • Excessive grooming

  • Scratching or biting at the skin


Dogs should be at least one month old and weight over 2 lbs before taking this medication. Capstar is an excellent short-term solution for fleas, but it won’t prevent fleas long-term like other oral flea medications which contain insect-growth regulators.

Do not flush Capstar tablets down the toilet or discard Capstar into the environment. This medication can contaminate the water supply and harms fish and beneficial insects.

Always double-check with your vet to make sure any new medication and supplements are safe for your dog. 

Drug interactions

No drug interactions have been reported with concurrent use of Capstar and other drugs. 

Allergic reactions and sensitivity

As with all medications, there’s a chance that allergic reaction and hypersensitivity can develop in dogs taking Capstar. Because of its chemical similarities to nicotine, nitenpyram sensitivity looks a lot like nicotine poisoning in mammals. Signs of a nitenpyram reaction are confusion, loss of coordination, seizures, respiratory distress, trembling, and loss of muscle control. 

Frequently asked questions

How long does it take Capstar to work for dogs?

Capstar takes effect within a half-hour of administration.

Can I use Capstar for dogs taking other flea preventatives?

Yes! Unlike most flea medicines on the market, Capstar is typically safe to combine with other parasite preventatives methods. This medication is safe to use with flea preventative collars, de-worming agents, topical flea drops, and oral flea medications. Just be sure to check the fine print on each product first.

Does Capstar have special storage instructions? 

Store unused Capstar tablets in their original blister packaging at room temperature and discard after the expiration date.  

Is Capstar safe for dogs that are pregnant or lactating?

Yes, studies show this medication is completely safe for mother dogs and puppies both during pregnancy and post-partum. 

Will Capstar help for dogs with flea allergies?

Yes, regular treatment with this medicine can prevent recurring flea reactions and prevent self-inflicted injuries due to skin irritation. 

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