Can morphine still be considered to be the standard for treating chronic pain? A systematic review including pair-wise and network meta-analyses

The current evidence is moderate, both in respect to the number of directly comparative studies and in the quality of reporting of these studies. No clear superiority in efficacy and tolerability of morphine over other opioids was found in pair-wise and network analyses. Based on these results, a justification for the placement of morphine as the reference standard for the treatment of severe chronic pain cannot be supported.