The best replacement for sentinel is heartgard.

The best alternatives to sentinel are rated as following:
★★★★★  heartgard
★★★★  interceptor
★★★★  trifexis
★★★★  revolution
★★★  frontline
★★  guardian
★★  adept
★★  savior
★★  marauder
★  scourge
★  sentinel spectrum
★  sentinel
★  purifier
★  vanguard
★  sentinel xs
★  gunslinger
★  iverhart max
★  comfortis
★  infiltrator
  revolution for dogs
  heartgard plus
  soldier
  zion
  advantage multi
  frontline plus
  vanguard me2
  optimus
  interceptor for dogs
  heartguard
  fernox
  advantage
  comboguard
  advantix

Your alternative for sentinel is not listed? Suggest!
Speaking about sentinel, one probably shouldn't forget about frontline.

Other search terms related to sentinel and their ratings are:
★★★★★ frontline
★★★★ comfortis
★★★★ advantix
★★ capstar
★ leatt
k9 advantix
leatt brace
You have in mind a companion for sentinel and it is not yet here? Propose!



Google Trends

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sentinel
heartgard
interceptor