How do drops on the neck region kill fleas? - briefly
Topical drops placed on the neck spread over the skin, releasing a neurotoxic insecticide that penetrates the flea’s cuticle and interferes with its nervous system, causing swift mortality. The systemic absorption also reaches feeding fleas, ensuring complete eradication.
How do drops on the neck region kill fleas? - in detail
Topical solutions applied to the cervical region are absorbed through the skin and enter the bloodstream, creating a systemic reservoir that reaches parasites feeding on the host. The active ingredients—commonly neurotoxic insecticides such as fipronil, imidacloprid, or selamectin—bind to specific receptors in the flea’s nervous system. Binding to GABA‑gated chloride channels (fipronil) or nicotinic acetylcholine receptors (imidacloprid) blocks normal ion flow, causing uncontrolled neuronal firing, paralysis, and death. Selamectin interferes with glutamate‑gated chloride channels, producing similar neurotoxic effects.
After application, the compound diffuses across the stratum corneum, enters the dermal capillaries, and circulates throughout the body. Fleas ingest the drug during blood meals; the concentration in the host’s plasma is sufficient to reach lethal levels within the parasite’s body. Because the drug remains in the bloodstream for several weeks, newly attached fleas encounter a toxic environment continuously, preventing population buildup.
Pharmacokinetic factors influencing efficacy include:
- Absorption rate: determined by the formulation’s solvent system and the animal’s skin thickness.
- Distribution volume: systemic spread ensures exposure of fleas on all body regions, not only the site of application.
- Elimination half‑life: longer half‑life sustains lethal concentrations, reducing the need for frequent re‑application.
- Metabolic stability: resistance to hepatic degradation preserves activity.
Safety considerations focus on selective toxicity. The compounds target insect-specific receptors that differ markedly from mammalian equivalents, minimizing adverse effects in the host. Proper dosing—based on body weight—prevents overdosing and reduces the risk of skin irritation or systemic toxicity.
In practice, a single dose applied to the neck provides continuous protection against fleas for up to a month, eliminating existing infestations and preventing new ones through the described neurotoxic mechanism.