How does Simparica work on fleas? - briefly
Simparica’s active ingredient, sarolaner, blocks parasite GABA‑ and glutamate‑gated chloride channels, leading to swift paralysis and death of fleas. One oral dose maintains efficacy for up to 35 days.
How does Simparica work on fleas? - in detail
Simparica contains the isoxazoline compound sarolaner, which is absorbed rapidly after oral administration. The drug reaches peak plasma concentrations within 2–4 hours and distributes throughout the body, including the skin and hair follicles where adult fleas feed.
Sarolaner acts as a selective antagonist of ligand‑gated chloride channels that are controlled by gamma‑aminobutyric acid (GABA) and glutamate. By blocking these channels, the compound disrupts inhibitory neurotransmission in the flea nervous system, leading to uncontrolled neuronal firing, paralysis, and death. The effect occurs within hours of the parasite ingesting blood containing the medication.
Key pharmacodynamic characteristics:
- Rapid onset: Flea mortality observed as early as 4 hours after the first dose.
- Sustained activity: Effective concentrations persist for at least 35 days, providing continuous protection without re‑dosing.
- Broad spectrum: Works against all adult flea stages, including those resistant to other classes of ectoparasiticides.
- Systemic distribution: Because the drug is present in the host’s bloodstream, fleas are exposed when they feed, eliminating the need for direct contact with the product.
Efficacy data from controlled studies show a reduction of flea counts by > 95 % within 24 hours of treatment and complete eradication of the infestation after a single monthly dose when administered at the label‑recommended weight‑based dosage (2 mg kg⁻¹). The systemic nature of the product also prevents re‑infestation from environmental sources, as any new fleas that bite the treated animal are killed before reproduction can occur.
Safety considerations include a wide margin of tolerance, with adverse events limited to mild gastrointestinal signs in a small percentage of treated dogs. The drug is not metabolized into active residues, and elimination occurs primarily via feces and urine, minimizing environmental impact.