Saints were well on their way to victory by half-time when they had already built-up a 19-0 advantage.
Centre Luther Burrell, Fijian second-row forward Api Ratuniyarawa and hooker James Fish all went in for tries with Dan Biggar adding two conversions.
Dragons made a fine start to the second period with centre Adam Warren winning the race to a grubber kick and fly-half Josh Lewis converted to give the visitors hope.
It was to prove a false dawn as Saints quickly responded with Burrell’s second and there was no way back for Dragons after that as Fijian winger Taqele Naiyaravoro helped himself to a brace of touchdowns.
Scrum-half Alex Mitchell and winger Ollie Sleightholme also crossed for tries while Dragons only other response was a touchdown by flanker Nic Cudd converted by Lewis three minutes from time.
Next Saturday Northampton visit Timisoara Saracens while Dragons travel to France to take on Clermont Auvergne