The toxicity profile of oxaliplatin, a platinum derivative currently used in the treatment of colorectal cancer, differs from those of the other platinum compounds, cisplatin and carboplatin. Oxaliplatin treatment induces an acute neurotoxicity characterized by a rapid onset of cold-induced distal dysesthesia and a chronic sensory peripheral neuropathy. A single intravenous dose of oxaliplatin produced a dose-dependent mechanical hyperalgesia and heat and cold allodynia; repeated administration intensified symptoms. A single intradermal dose of oxaliplatin produced a dose-dependent mechanical hyperalgesia. A single dose intravenous oxaliplatin also lowered thresholds and increased responses of C-fiber nociceptors to mechanical stimulation, confirming a peripheral site of action. Whereas peripheral administration of inhibitors of second messengers implicated in models of other painful peripheral neuropathies (PKA, PKC, NO, Ca(2+), and caspase) had no effect; both systemic and local administration of antioxidants (acetyl-L-carnitine, alpha-lipoic acid or vitamin C), all markedly inhibited oxaliplatin-induced hyperalgesia. Intrathecal administration of the neurotoxin for IB4-positive nociceptors, IB4-saporin, markedly attenuated IB4 staining in the dorsal horn of the spinal cord and completely prevented oxaliplatin-induced hyperalgesia. We suggest that oxaliplatin acts on IB4 (+)-nociceptors to induce oxidative stress-dependent acute peripheral sensory neuropathy.

Perspective: Many drugs used to treat cancer produce pain as their dose-limiting side effect. We used a model of this pain syndrome induced by oxaliplatin to demonstrate that pain is produced by action on a subset of nociceptors, the IB4-positive DRG neurons. This information could help define cellular targets against which protective therapies could be developed.