We use Revolution from our vet which covers heartworm, fleas and ticks. It's administered once a month, one drop between the shoulder blades, and it's used from May to Oct.
Koozer has been on Sentinel and does awesome! However, it's no longer available so the vet switched to Trifexis. I started a new thread about it, but thought I could get some responses on this thread from those of you who used Sentinel...what do you use now? And what do you think of Trifexis? We have 1 more month left of the Sentinel so I want to get good info before switching him over.