Intrathecal resiniferatoxin may decrease cancer pain intensity and reduce opioid consumption: NEJM

A new study published in The New England Journal of Medicine Evidence showed that for patients with unmanageable cancer pain, single dose of intrathecal resiniferatoxin (RTX), an opioid-sparing analgesic may be effective.

Even with thorough medical care, a significant portion of patients with advanced cancer experience refractory pain. A powerful member of the capsaicin-containing medication family, resiniferatoxin selectively and permanently kills the neurons (or their axons) that convey chronic pain. In a number of animal species, intrathecal injection of RTX has shown a high degree of safety, specificity, and effectiveness in alleviating severe pain.

In this study, Andrew Mannes and colleagues assessed resiniferatoxin (RTX), a nonopioid analgesic that selectively blocks nociceptive activity sent by a subset of dorsal root ganglion neurons. RTX is a strong agonist of the transient receptor potential vanilloid 1 (TRPV1) ion channel.

This is an interim analysis of a first-in-human, open-label, Phase 1 research in which 19 patients with lower extremity and/or abdominal refractory cancer pain received a single intrathecal RTX dosage. Safety was the main result. A numerical rating scale assessing the "worst pain" during a 24-hour period was used to evaluate effectiveness during the research, which produced secondary outcomes. On this scale, 0 represents "no pain" and 10 represents "worst pain imaginable." The amount of opioids needed to manage pain was assessed in morphine equivalents.