Frontline (fipronil) is labeled for the treatment of fleas, ticks, and lice on dogs and cats.  Frontline has a wide margin of safety for most mammals, but rabbits are an exception. Using it on them can cause them to be sick, potentially fatally. The Frontline package insert actually contains the warning to not use the product on rabbits; nonetheless, many rabbit owners are still unaware of the risks.

Numerous reports exist of young or small rabbits that were treated with fipronil and within 24 hours exhibited signs of anorexia and lethargy, with or without seizures, or died.

Young rabbits are reported to be more sensitive to the effects of than older ones. Seizures are often not seen until 3-9 days after exposure. Death may not occur for a week or two after exposure.

In the event of known application, whether accidental or intentional, the rabbit should be treated for topical cutaneous exposure. When rabbits lick the product while grooming, they absorb 30-50% of it, compared to absorbing only 0.07% of it just from being on their skin. The rabbit should be bathed in warm water with a mild puppy/kitten shampoo, towel-dried afterwards, and then placed in a warm incubator to dry. While this could be done at home, a rabbit showing clinical signs should be at the clinic for supportive care. In addition, the use of activated charcoal may be a good idea because rabbits rapidly groom off any product applied topically, so they are likely to ingest Frontline.

By the time a rabbit is showing clinical signs, prognosis for recovery is guarded, but bathing and activated charcoal should still be attempted. Supportive care should include fluid therapy and force feeding. If the rabbit has seizures, he should be controlled with anti-seizure medications such as Valium or midazolam. If there is no improvement in the first 72 hours, then the prognosis for recovery is guarded.