Another vote for Trifexis, which is currently about the best thing going for fleas and heartworm prevention. The downside is that Trifexis is poor for ticks--use Frontline here, or even better, a Preventic collar.
Some dogs will vomit up the Trifexis tablet, even if given with food. One of our dogs throws up Trifexis, so we're currently using topical Revolution, along with Preventic collars here in EasTex.
"For every complex problem there is an answer that is clear, simple.....and wrong." H. L. Mencken