The tick walked normally at first, staggered in 10 minutes, and was dead (or at least incapable of moving) in 20 minutes. Poor sirius!nexgard works by killing the tick after it attaches and ideally kills the tick before it can inject infectious organisms like lyme. About A New Flea And Tick Control Nexgard Fleas Flea And Tick Pet Shed Oral medication for ticks won't be able to stop a tick from biting. How does nexgard work on ticks . Whereas, nexgard spectra contains both. See product label for full claim details and directions for use. The active substance in nexgard, afoxolaner, acts as an ‘ectoparasiticide’. Nexgard also treats and controls three of the most common mange causing mites affecting dogs: Demodex mites, sarcoptes mites and ear mites. Hi, thanks for using petcoach! An insecticide and acaricide that attacks the central nervous system of invertebrates, afoxolanerstarts to work fast to kill fleas within four hours of ingestion and continues working ...