Pentazocine, sold under the brand name Talwin among others, is an analgesic medication used to treat moderate to severe pain. It is believed to work by activating (agonizing) Îș-opioid receptors (KOR) and ÎŒ-opioid receptors (MOR). As such it is called an opioid as it delivers its effects on pain by interacting with the opioid receptors. It shares many of the side effects of other opioids like constipation, nausea, itching, drowsiness, and respiratory depression, but, unlike most other opioids, it fairly frequently causes hallucinations, nightmares, and delusions. It is also, unlike most other opioids, subject to a ceiling effect, which is when at a certain dose no more pain relief is obtained by increasing the dose any further.
Chemically it is classed as a benzomorphan and it comes in two enantiomers, which are molecules that are exact (non-superimposable) mirror images of one another.