One of the most common points of confusion for patients exploring ketamine-based treatments is the relationship between intravenous ketamine infusion and esketamine nasal spray. Both involve ketamine-derived compounds, both work through the glutamate system, and both are used for treatment-resistant depression. But they are not the same treatment, and the differences between them are clinically meaningful in ways that affect which option is most appropriate for different patients. Understanding these differences, and how a specialist psychiatric team approaches the choice between them, is increasingly relevant as both options have become more widely available in New York City. The Pharmacological Relationship Ketamine is a racemate, meaning it is a mixture of two mirror-image molecular forms known as enantiomers: the R-enantiomer and the S-enantiomer. Esketamine, the active ingredient in Spravato, is the pure S-enantiomer.…