Ketamine infusion therapy is a rapid-acting intervention for individuals struggling with Treatment-Resistant Depression (TRD). It involves the precise, low-dose intravenous administration of the medication in a monitored clinical setting. Unlike conventional antidepressants, ketamine often provides relief from severe depressive symptoms within hours or days. The therapy works by modulating the brain’s glutamate system, specifically targeting the N-methyl-D-aspartate (NMDA) receptors. This action promotes neuroplasticity, helping to repair communication pathways between brain cells linked to mood and cognition.
The Initial Induction Phase
The first step in ketamine therapy is the induction phase, an intensive series of treatments designed to achieve a rapid and cumulative therapeutic effect. The standard protocol typically involves four to six infusions administered over a period of about ten to fourteen days. This concentrated schedule is modeled after clinical trials and aims to achieve a “saturation” of the therapeutic effect in the brain.
A common frequency for this initial series is receiving the infusion every other day or approximately three times per week. This schedule is necessary because a single ketamine infusion, while fast-acting, often provides short-lived benefits. By stacking the infusions closely together, clinicians build upon the neuroplastic changes initiated by each dose, leading to more sustained symptom relief.
The antidepressant effects of ketamine are known to be cumulative. Patients often report noticeable improvement after the first or second session, but the full therapeutic benefit is usually not realized until the fourth to sixth infusion. Administering the treatment in this structured series maximizes the chance of achieving a significant reduction in depressive symptoms. The six-session, two-week model remains the most common starting point for individuals with TRD.
Assessing Response and Transitioning Care
Following the initial series, the next step is determining whether the patient has responded sufficiently to the treatment. Clinicians rely on patient self-reporting and standardized psychometric tools to objectively measure symptom severity. These tools include scales like the Montgomery-Åsberg Depression Rating Scale (MADRS) or the Quick Inventory of Depressive Symptomatology (QIDS).
The success of the induction phase is categorized into two benchmarks: “response” and “remission.” A patient achieves a response if their depression rating score decreases by 50% or more from their baseline score. Remission is the goal, meaning a near-total resolution of depressive symptoms, often indicated by a score falling below a specific threshold.
The assessment results dictate the patient’s path forward. If a patient achieves a robust response or remission, they transition to a less frequent maintenance schedule to preserve their gains. If a patient does not respond adequately after the initial series, the clinician may consider minor adjustments, such as a slight dose increase or one or two additional sessions, before concluding the treatment is ineffective.
Maintenance Treatment Schedules
For patients who experience a positive outcome during the induction phase, the focus shifts to a maintenance schedule designed to prevent symptom recurrence. This ongoing phase is highly personalized and aims to find the lowest effective frequency of “booster” infusions needed to sustain the antidepressant effect. The total number of infusions a patient receives over a year depends entirely on their individual symptom stability.
The process involves gradually tapering the frequency of treatments over time. A typical maintenance schedule might begin with a booster infusion once per week, which is then stretched to once every two weeks, and eventually to a monthly or less frequent schedule. The ultimate goal is to maximize the time between sessions, often called the “ketamine holiday,” while maintaining symptom control.
The need for a booster infusion is often signaled by the subtle return of depressive symptoms, such as reduced mood, loss of energy, or sleep disruption. For some individuals, a single booster session restores the therapeutic effect for several weeks or months. Other patients with more chronic symptoms may require a more consistent, recurring schedule, such as one infusion every four to six weeks, to remain in remission.