Esketamine, sold under the brand name Spavato, was approved in March 2019 for the treatment of major depressive disorder and treatment-resistant depression in adults. It is a fast-acting antidepressant and is approved for use only with other antidepressants. In addition, the drug must be administered in an in-patient setting and the prescription cannot be taken home with the patient. The reason for this is because of side-effects such as dissociation, sedation, confusion, visual disturbances, etc. This drug is prepared and administered as a nasal spray. Esketamine is the S+ enantiomer of ketamine. This drug works primarily by non-competitively antagonizing NMDA receptors. It also has an off-target effect of inhibiting dopamine transporters leading to an increase of dopamine activity in the CNS. This drug is an important therapeutic because it is an option for patients who are resistant to other antidepressant medications. In addition, its rapid antidepressant effect is important because traditional antidepressants usually have a slow onset after repeated administration (i.e. SSRI’s must be taken for several weeks before they are fully effective), while esketamine provides a rapid therapeutic effect (within 24 hours) which can be very important for patients suffering from debilitating depression.