Amazon Basics Flea and Tick Topical Treatment and Prevention for Extra Large Dogs (89-132 lbs), Kills Fleas and Ticks, Waterproof, Monthly Application, 6 Count, Packaging May Vary

You could use Heartgard from Allivet, $109/yr Generic Frontline Plus from Amazon, 89-129 lbs Use 1/2 ampule each month $24/yr https://a.co/d/0fClrmHO I don't know why people buy expensive flea/tick/ heartworm meds. I have three large dogs and am surrounded by woods with ticks, mosquitos, etc. This regimen works well for my dogs. I never find attached ticks on my creatures. They've never had fleas. I use two ampules for my 3 dogs each month. And 2 1/2 Heartgard Chews. Even with 2 large and one med sized dog I pay $400/yr for preventatives that are effective.