How does Stronghold act on fleas? - briefly
Stronghold (selamectin) is applied to the skin, where it is absorbed and spreads systemically to disrupt flea nerve function, leading to paralysis and death. A single dose provides continuous protection for up to a month.
How does Stronghold act on fleas? - in detail
Stronghold contains the insecticide imidacloprid, a neonicotinoid that binds selectively to insect nicotinic acetylcholine receptors. Binding blocks normal neurotransmission, causing rapid paralysis and death of the flea. Because the compound is highly specific for insect receptors, it does not affect mammalian nervous systems at the recommended dose.
After a single topical application, the solution spreads across the animal’s skin and enters the superficial lipid layer. From there the active ingredient diffuses into the bloodstream. When a flea feeds, it ingests imidacloprid directly from the host’s blood, delivering a lethal dose within minutes. The drug also distributes to the skin surface, exposing fleas that crawl over the coat without feeding.
The product acts on all flea life stages that contact the treated animal:
- Adult fleas feeding on blood are killed within 30 minutes.
- Female fleas that have already begun egg production are prevented from completing oviposition; fewer eggs are laid.
- Eggs deposited on the host’s fur are exposed to residual imidacloprid, resulting in a 90‑95 % reduction in hatchability.
- Emerging larvae that move onto the host for feeding are eliminated before they can develop into pupae.
Efficacy persists for up to 30 days. Clinical studies show 100 % kill of existing adult fleas within the first day and sustained control of new infestations throughout the month. The drug’s half‑life on the skin surface allows continuous exposure without the need for re‑application during the treatment interval.
Safety data indicate low systemic toxicity in dogs and cats. Imidacloprid is metabolized primarily by hepatic enzymes and eliminated in urine. The formulation does not interfere with other common ectoparasitic treatments, allowing concurrent use when indicated.