Products
Fipronil is commercially available in many countries as a drop-on solution (spot-on) and as a spray for dogs and cats (e.g., Frontline, Eliminall). It is available as a veterinary drug and has been approved since 1995. Fipronil is also included in combination preparations together with the juvenile hormone analog S-methoprene, which inhibits the development of immature stages of insects, thus additionally killing eggs and larvae (Frontline Combo).
Structure and properties
Fipronil (C12H4Cl2F6N4OS, Mr = 437.1 g/mol) is a lipophilic, fluorinated and chlorinated phenylpyrazole derivative. It exists as a white powder with a musty odor that is poorly soluble in water. Fipronil is structurally closely related to its successor pyriprole (Prac-tic).
Effects
Fipronil (ATCvet QP53AX15) is a broad-spectrum insecticide that kills fleas, lice, ticks, hair lice, cockroaches, termites, ants, fire ants, and mole crickets, among others. Insecticidal and acaricidal effects are due to binding and inhibition of GABA chloride channels, resulting in central nervous system overstimulation and death. Fipronil is effective for several weeks in dogs and cats because it is distributed throughout the coat via the sebum, binds well to the coat, and is released continuously from the sebaceous glands over a long period of time. Only a small percentage (< 1%) of the active ingredient is absorbed into the body. Thus, it does not act from the blood as, for example, lufenuron (Program).
Indications
Fipronil is used in cats and dogs to prevent and treat infestations of fleas, ticks, and hair lice and to treat allergic flea dermatitis.
Dosage
According to the package insert. The dose is based on body weight in dogs. Spot-on preparations are administered directly to the skin on the back of the animals. Directions for use:
- Frequent bathing and washing may reduce the effectiveness, especially shortly after treatment.
- The drug should not get on the skin, mucous membranes or in the eyes in humans.
- Freshly treated animals can transfer the drug to humans. Therefore, too close contact should be avoided, especially in children.
Contraindications
Fipronil should not be used on animals that are too young, sick, injured or convalescing. Medicines for dogs are not suitable for cats, as overdose is possible. Fatal outcome may occur in rabbits. Refer to the drug label for complete precautions.
Interactions
Fipronil should not be used concomitantly with other insecticides. Piperonyl butoxide may antagonize the effects of fipronil.
Adverse effects
Possible adverse effects include increased salivation, skin reactions at the administration site, itching, hair loss, and rarely central nervous disturbances. Overdose should be avoided as it leads to neurotoxicity with tremors, overexcitation, convulsions and death. Fipronil, like other pesticides, is not uncontroversial as a veterinary drug. The safety and tolerability of the active ingredient is doubted in the literature by some authors (e.g. Cox, 2005). Criticisms include organ toxicity, deposition in fur, and poor ecological compatibility.
