You can try something like this:

vec_set(temp,my.x);
c_move(me,...)
vec_sub(temp,my.x);
vec_scale(temp,-1); //facing in the wrong direction

effect(..., temp);

The particles now have the velocity from your entity. This may lead to weird looking results when changing the entity's direction, though.
Instead I would try to keep the particle's lifespan really short.