Sodium channel blocker rotation for refractory neuropathic pain

OBJECTIVES: To investigate the efficacy and safety of sodium channel blocker (SCB) rotation and/or combined use for neuropathic pain where the initial SCB is ineffective or poorly tolerated. METHODS: A retrospective chart review of SCB rotation in a single palliative care centre. We reviewed the notes of those receiving two or more SCBs for pain. All clinical notes and medication administration records were examined to ascertain efficacy and tolerability. RESULTS: We found 45 examples of SCB rotation in 32 patients. Most (81%) had metastatic cancer. All had tried multiple other analgesics. Most (29/45) were rotated for persistent pain; the remainder for poor tolerability (11/45) or to change the route (5/45), for example, an SCB that could not be given parenterally when the oral route was lost. SCB rotation appeared helpful for the majority (69%). Switches appeared effective in both directions between lacosamide and oxcarbazepine; thus, neither SCB appeared 'superior'. A minority (7/32) received two SCBs together having had insufficient analgesia from SCB monotherapy; dual SCB therapy was well tolerated and appeared effective in 6/7. CONCLUSIONS: Rotation appeared effective and well tolerated for neuropathic pain where an initial SCB was ineffective or poorly tolerated. Further, in those with the most analgesic-refractory pains, we found preliminary evidence that combining SCBs with different characteristics might be beneficial, for example, combining slow channel inactivators with fast channel inactivators. Thus, we believe that SCBs should not be considered a homogenous analgesic class and that further research into both SCB rotation and dual SCB therapy is justified.