This study is testing a drug called Tetrodotoxin (TTX) for treating neuropathic pain (nerve pain) caused by chemotherapy, a treatment for cancer. The study is randomized and double-blind, meaning neither the participants nor the researchers know who is getting the real drug and who is getting a placebo (a harmless pill with no medicine). To join, you must be 21 or older, have stable, moderate to severe pain from past chemotherapy, and not have any actively growing cancer.

The study lasts for about 13 weeks, including a 4-day treatment and weekly follow-ups. You must not have other types of neuropathy (like from diabetes) and must not take certain medications that may interfere with the study. It's important to discuss with your doctor if you have other medical conditions or are taking other medications.

• The study lasts for 13 weeks, including treatment and follow-ups.
• Participants need to have stable moderate to severe pain from past chemotherapy.
• Certain medications and medical conditions can exclude you from joining.