Esketamine is a rapid-acting antidepressant developed as the S-enantiomer of ketamine and approved for medical use in the United States in 2019 as an intranasal therapy for treatment-resistant depression and depressive symptoms in adults with acute suicidal ideation or behavior. Its development was driven by the need for faster-acting antidepressants compared to traditional monoaminergic agents, with a mechanism involving NMDA receptor antagonism leading to increased glutamatergic signaling and synaptic plasticity. While it has demonstrated significant effectiveness in rapidly reducing depressive symptoms, its clinical use is carefully regulated due to risks of dissociation, sedation, dizziness, and potential for misuse. As a result, it is administered under a Risk Evaluation and Mitigation Strategy (REMS) program requiring supervised healthcare setting administration and post-dose monitoring. Esketamine is used as part of combination therapy with oral antidepressants and is delivered via a nasal spray formulation, reflecting its controlled and closely monitored therapeutic profile.
BRAND NAMES
Spravato (intranasal formulation for treatment-resistant depression and depressive symptoms with acute suicidal ideation or behavior).
MECHANISM OF ACTION
Esketamine is a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, a subtype of glutamate receptor in the central nervous system. By blocking NMDA receptors on inhibitory interneurons, it leads to a transient increase in glutamate release, which subsequently stimulates AMPA receptors.
PHARMACOKINETICS
Absorption
Esketamine is administered primarily as an intranasal spray, where it is rapidly absorbed through the nasal mucosa. It has relatively high bioavailability compared to oral administration because it bypasses first-pass hepatic metabolism.
Distribution
Esketamine has a large volume of distribution, indicating extensive tissue uptake beyond the plasma compartment. It is highly lipophilic and rapidly crosses the blood–brain barrier, resulting in significant central nervous system distribution, which contributes to its rapid antidepressant effects.
Metabolism
Esketamine is extensively metabolized in the liver, primarily by cytochrome P450 enzymes, especially CYP2B6 and CYP3A4, with minor contributions from CYP2C9 and CYP2C19.
Elimination
Esketamine and its metabolites are primarily eliminated through the kidneys in the urine, with most of the dose excreted as inactive, water-soluble metabolites formed after hepatic biotransformation.
PHARMACODYNAMICS
Esketamine exerts its antidepressant effects primarily through non-competitive antagonism of the NMDA receptor, a subtype of glutamate receptor in the central nervous system. By blocking NMDA receptors on inhibitory interneurons, it increases glutamate release, which enhances stimulation of AMPA receptors and activates downstream signaling pathways involved in synaptic plasticity.
ADMINISTRATION
Esketamine is administered as a prescription-only intranasal spray under direct medical supervision. It is given in a certified healthcare setting due to risks such as sedation, dissociation, and temporary increases in blood pressure.
DOSAGE AND STRENGTH
Esketamine is supplied as a single-use intranasal spray device in a strength of 28 mg per device (delivering two sprays of 14 mg each). The usual dosing regimen for treatment-resistant depression begins with an induction phase of 56 mg or 84 mg administered twice weekly, depending on patient response and tolerability.
DRUG INTERACTIONS
Esketamine has clinically significant drug interactions primarily due to its central nervous system effects and hepatic metabolism via CYP2B6 and CYP3A4 enzymes. Concomitant use with CNS depressants such as benzodiazepines, opioids, or alcohol can enhance sedation, dizziness, and dissociative effects.
FOOD INTERACTIONS
Esketamine has minimal direct food interactions because it is administered as an intranasal spray rather than orally. However, food intake can indirectly influence its effects by affecting nausea, blood pressure stability, and overall tolerability during treatment.
CONTRAINDICATIONS
Esketamine is contraindicated in patients with known hypersensitivity to esketamine, ketamine, or any component of the formulation. It should not be used in individuals with aneurysmal vascular disease (including intracranial, thoracic, or abdominal aorta aneurysms) or a history of intracerebral hemorrhage due to its potential to increase blood pressure.
SIDE EFFECTS
Dissociation (feeling detached from reality or self)
Dizziness or vertigo
Sedation or drowsiness
Increased blood pressure (transient hypertension)
Nausea and vomiting
Headache
Anxiety or agitation
OVER DOSAGE
Overdose of Esketamine is uncommon due to its controlled administration in a supervised healthcare setting. However, excessive exposure can intensify its pharmacological effects, leading to marked central nervous system depression, severe dissociation, sedation, agitation, confusion, dizziness, nausea, and vomiting.
TOXICITY
Toxicity of Esketamine is primarily related to excessive central nervous system stimulation and cardiovascular effects rather than direct organ damage. At high doses or with misuse, it can cause pronounced dissociation, severe sedation, confusion, agitation, and perceptual disturbances.
