Treatment-Resistant Depression

Treatment-resistant depression (TRD) affects approximately one-third of the 21 million adults in the United States diagnosed with major depressive disorder. It is defined as depression that has not adequately responded to at least two different antidepressant treatments of adequate dose and duration.

For decades, patients with TRD had limited options. Standard antidepressants like SSRIs and SNRIs work by gradually modulating serotonin and norepinephrine levels, often requiring 4–8 weeks to show effects — and for many patients, these medications never provide adequate relief. The personal toll is devastating: increased risk of suicide, inability to work, strained relationships, and a profoundly diminished quality of life.

Ketamine has emerged as one of the most significant breakthroughs in psychiatric treatment in over 50 years, offering rapid relief — often within hours — where conventional treatments have failed.

Unlike traditional antidepressants that target serotonin or norepinephrine, ketamine works primarily through the glutamate system — the brain's most abundant excitatory neurotransmitter. Specifically, ketamine blocks NMDA (N-methyl-D-aspartate) receptors, leading to a cascade of neurobiological effects:

• Rapid synaptogenesis: Ketamine triggers the release of brain-derived neurotrophic factor (BDNF) and activates the mTOR signaling pathway, promoting the rapid growth of new synaptic connections in the prefrontal cortex — an area severely affected by chronic depression.
• Glutamate surge: By blocking NMDA receptors on inhibitory interneurons, ketamine causes a burst of glutamate release that activates AMPA receptors, strengthening neural circuits weakened by depression.
• Anti-inflammatory effects: Emerging research suggests ketamine reduces neuroinflammation, which is increasingly recognized as a contributing factor in treatment-resistant depression.
• Default mode network modulation: Ketamine alters activity in the brain's default mode network, which is hyperactive in depression and associated with rumination and negative self-referential thinking.

The standard protocol for treating TRD with ketamine typically involves:

• Induction phase: 6 infusions administered over 2–3 weeks (typically Monday/Wednesday/Friday). Each IV infusion delivers 0.5 mg/kg over 40 minutes.
• Assessment: Response is evaluated after the induction series. Most responders notice improvement by the second or third infusion.
• Maintenance phase: Responders transition to maintenance infusions, typically starting at every 2–4 weeks and adjusting based on individual response. Some patients maintain benefits with monthly infusions, while others require more frequent sessions.
• Alternative routes: Spravato (esketamine nasal spray) is FDA-approved for TRD and may be used as an alternative or complement to IV infusions. Oral and sublingual formulations are also used in some protocols.

Treatment should be administered alongside ongoing psychotherapy and, in many cases, continued use of oral antidepressants for optimal outcomes.

Ketamine therapy for depression is generally well-tolerated when administered in a clinical setting. Important safety considerations include:

• Common side effects: Dissociation, dizziness, nausea, elevated blood pressure, and blurred vision during infusion. These typically resolve within 1–2 hours.
• Cardiovascular monitoring: Blood pressure and heart rate should be monitored throughout treatment, as ketamine can cause transient hypertension.
• Contraindications: Uncontrolled hypertension, active psychosis, untreated hyperthyroidism, and certain cardiac conditions.
• Abuse potential: While ketamine does have abuse potential, this risk is minimal in the context of medically supervised, clinic-based treatment at sub-anesthetic doses.
• Bladder concerns: Cystitis is associated with chronic recreational ketamine abuse at high doses but has not been reported at clinical treatment doses and frequencies.