Esketamine and ketamine are perioperative analgesics and anesthetics widely used in Europe and the United States, but their application in China is still in early stages. They primarily act through non-competitive antagonism of the N-methyl-D-aspartate receptor (NMDAR), though they also affect multiple other receptors and pathways. Due to potential side effects and addictive properties, they are subject to regulatory controls. This review synthesizes recent research on their classical applications—analgesia, sedation, and anesthesia—as well as emerging antidepressant, anti-tumor, and anti-inflammatory effects. By integrating preclinical and clinical findings and considering limitations, the review aims to inform clinical use and future research directions for these versatile agents.
Chronic recreational nitrous oxide use can cause functional vitamin B12 deficiency and neuropsychiatric complications. In a review of 16 patients aged 17–25, all had neurological symptoms like limb numbness, unsteady gait, and weakness; 12 also had psychiatric symptoms including hallucinations, agitation, depression, and personality changes. Twelve patients had vitamin B12 deficiency, and all 16 had elevated homocysteine levels. Fourteen showed abnormal spinal cord signals on MRI. Symptoms improved with vitamin B12 treatment and stopping nitrous oxide use. Clinicians should recognize nitrous oxide as a cause of neuropsychiatric problems in young adults.