Time underestimation caused by (S)-ketamine may be linked to its antidepressant effects, but this came with severe behavioral disruption. The authors propose that behavioral disruption induced by psychedelics objectively indicates their psychotomimetic-like actions.
Ketamine isoforms (R-, S-, and racemic R,S-) do not produce opioid- or cannabis-like subjective effects and are unlikely to fully mask the interoceptive effects of morphine or THC. In rats trained to discriminate morphine or THC from vehicle, none of the ketamine isoforms fully blocked the discriminative stimulus effects of morphine or THC, nor did they fully substitute for either drug. Ketamine isoforms did not alter response rates in the morphine experiment but suppressed responding in the THC experiment, suggesting coadministration with cannabinoids may lead to pronounced sedative-like suppression. These findings warrant further investigation into the safety and interaction profiles of such drug combinations.