Duncan Casey made the most of a late call-up into the starting 15 with two tries in Munster's bonus point win in Newport.
Argentina international Eusebio Guinazu had been due to make his Munster debut at hooker but was forced to withdraw because of a back problem.
Casey (below) took full advantage of Guinazu's misfortune, scoring two second-half tries as Munster ran in five unanswered scores against the struggling Welsh region.
Robin Copeland, Andrew Smith and Ronan O'Mahony were all on the scoresheet, with out-half Ian Keatley adding 13 points with the boot.
Geraint Jones had kicked the Dragons into an early lead with a penalty before Munster No 8 Copeland, fresh from making his Ireland debut against Georgia, powered over from close range.
Jones put the home side back into the lead with a second penalty before adding a third five minutes before half-time.
But a far more composed Munster appeared after the interval and they were soon back in front from a Keatley penalty.
The visitors' second try came shortly after when Casey was driven over from a lineout, with Keatley adding the extras.
Smith settled the nerves with their third try, making the most of an overlap out wide to break the line and race clear under the posts. Keatley added the conversion before Jones kicked his fourth penalty three minutes later to reduce the deficit to 12 points, but it was little more than a brief moment of relief.
Casey wrapped up the bonus point with a second try from a driving lineout before O'Mahony grabbed a fifth in the dying moments.
Dragons - G Jones, T Morgan, R Wardle, A Smith, H Amos, D Jones, R Rees (J Evans 60); B Harris, E Dee (T Thomas 79), D Way (L Fairbrother 65), C Hill, R Landman (capt), J Thomas, N Cudd (O Griffiths 64), Evans.
Munster - JJ Hanrahan; A Conway (Murphy 38), A Smith (P Howard 71), D Hurley, R O'Mahony; I Keatley, C Sheridan (D Williams 58); J Ryan (A Cotter 73), D Casey (N Scannell 73)), S Archer (B Botha 73); Donncha O'Callaghan (capt, Dave O'Callaghan 73), B Holland; P Butler, S Dougall (C Stander 58), R Copeland.
Ref - M Liperini (Italy)