How does a flea tablet work in dogs? - briefly
The tablet releases a systemic insecticide that is absorbed into the dog’s bloodstream, distributing throughout the body. When a flea bites, it ingests the toxin, causing immediate death or preventing reproduction.
How does a flea tablet work in dogs? - in detail
Flea oral medications for dogs contain systemic insecticides that are absorbed through the gastrointestinal tract after ingestion. The active compounds—commonly isoxazolines such as fluralaner, afoxolaner, or sarolaner—enter the bloodstream and distribute throughout the body’s tissues, including skin and hair follicles where adult fleas feed.
Absorption and distribution
- Tablet dissolves in the stomach, releasing the active ingredient.
- Compound penetrates the intestinal wall via passive diffusion.
- Blood circulation carries the molecule to peripheral sites, achieving concentrations sufficient to affect feeding parasites.
Mode of action
- Isoxazolines bind selectively to ligand‑gated chloride channels (GABA‑ and glutamate‑gated) in the nervous system of fleas.
- Binding blocks inhibitory neurotransmission, causing uncontrolled neuronal firing.
- Resulting hyperexcitation leads to rapid paralysis and death of the parasite within minutes to a few hours after it ingests treated blood.
Pharmacokinetic profile
- Peak plasma levels are reached within 2–4 hours post‑dose.
- Half‑life ranges from 12 days (afoxolaner) to 12 weeks (fluralaner), providing extended protection from a single administration.
- Metabolism occurs primarily in the liver; metabolites retain activity against fleas.
- Excretion is mainly fecal, with minimal renal elimination, reducing risk of accumulation in dogs with normal kidney function.
Efficacy against life stages
- Adult fleas die after feeding on treated blood; the drug does not affect eggs or larvae in the environment.
- Continuous systemic presence prevents re‑infestation by killing newly acquired adults before they reproduce.
Safety considerations
- Selective targeting of insect GABA receptors minimizes impact on mammalian nervous systems.
- Common adverse effects are mild gastrointestinal upset; severe reactions are rare.
- Dosage is calculated per kilogram body weight to avoid overdosing.
Resistance management
- Rotating products with different chemical classes can mitigate development of resistance.
- Monitoring for reduced efficacy is essential in areas with known resistant flea populations.
In practice, a single oral dose delivers sustained plasma concentrations that incapacitate fleas feeding on the host, breaking the infestation cycle without the need for topical sprays or environmental treatments. Proper dosing, adherence to the recommended interval, and integration with environmental control measures ensure maximal long‑term protection.