(2R,6R)-Hydroxynorketamine is a ketamine metabolite that has rapid antidepressant activity without ketamine-related side effects. The NMDAR antagonist (R,S)-ketamine must be metabolized to (2S,6S;2R,6R)-hydroxynorketamine (HNK) to have antidepressant effects. The (2R,6R)-HNK enantiomer appears to be the enantiomer most responsible for antidepressant effects in a mouse study and unlike (2S,6S)-HNK, (2R,6R)-HNK caused no significant changes in locomotion or coordination. (2R,6R)-HNK does not seem to have the same addiction potential as ketamine, since mice did not self-administer pharmacologically relevant doses of (2R,6R)-HNK under the same conditions where ketamine was readily self-administered. The (2R,6R)-HNK antidepressant appears to involve activation of AMPA glutamate receptors rather than inhibition of NMDA glutamate receptors.
