How Long Does It Take For Nexgard Spectra To Work On Ticks. Usually, nexgard starts killing fleas within 8 hours of exposure and ticks within 48 hours of exposure. Nexgard spectra once given provides protection for an entire month from fleas and ticks.nexgard starts killing fleas in as little as four hours after administering and 48 hours for ticks.nexgard starts to work within just 4 hours and will kill.
Nexgard spectra has been shown to be 100% effective at preventing flea tapeworm infestation for a full month. The tasty chewable is a monthly treatment given to destroy fleas and ticks on dogs. Nexgard spectra is an oral form of flea treatment for dogs and it provides the complete protection against fleas, ticks, heartworms, and intestinal worms through regular monthly treatments.