(+)-Naloxone (dextro-naloxone) is a drug which is the "unnatural" enantiomer of the opioid antagonist drug (−)-naloxone. Unlike "normal" naloxone, (+)-naloxone has no significant affinity for opioid receptors, but instead has been discovered to act as a selective antagonist of Toll-like receptor 4. This receptor is involved in immune system responses, and activation of TLR4 induces glial activation and release of inflammatory mediators such as TNF-α and Interleukin-1.