Never heard of malaria on the north coast, sometimes there are SOME cases of malaria in Punta Cana, altough I doubt these cases will be enough to describe a malaria drug, as you sad the malaria drug can have some very bad side effects and they normally only prescribe it if it's really necessary (for example if you stay les then 3/4 days in a malaria area, then they dont prescribe malaria pills)
As far as I know, there is only malaria (on a consistent basis) in the middle of the DR, close to the border with Haiti (small area).
Here in Holland they dont advice you to take malaria pills for the DR, unless you go to that area (but hardly anybody is going there, it's not a tourist place)
But DO you use insect repellent, with 30% DEET, especially during sunset, also try to cover your feet/ankles by this time.