Opioid antagonist

However, the analgesic effects from these specific drugs are limited and tend to be accompanied by dysphoria, most likely due to additional agonist action at the κ-opioid receptor.

This is the only treatment available which can reverse the long-term after effects of opioid addiction known as post acute withdrawal syndrome, which otherwise tends to produce symptoms such as depression and anxiety that may lead to eventual relapse.

These are designed to specifically inhibit certain opioid receptors in the gastrointestinal tract and with limited ability to cross the blood–brain barrier.

A variety of partial agonists or mixed agonists-antagonists of the MOR and KOR are also marketed, and include butorphanol, levorphanol, nalbuphine, pentazocine, and phenazocine.

With the sole exception of nalorphine, all of the preceding are used as analgesics (by virtue of the fact that both MOR and KOR agonism independently confer pain relief).

[4] The findings of a 2005 naltrexone study were slightly less promising, with an average of a 30% reduction of symptoms, as measured by three validated dissociation scales.