Continuous and Multi-Day Ketamine Infusions: Extended Protocols

What Are Continuous Ketamine Infusions?

Continuous ketamine infusions are extended intravenous ketamine protocols in which the medication is administered over a prolonged period — typically ranging from several hours to multiple consecutive days. Unlike the standard 40-minute ketamine infusion used for depression, continuous infusions deliver ketamine at a sustained rate over an extended duration, often requiring inpatient hospitalization or intensive outpatient monitoring.

These protocols are used primarily for severe chronic pain conditions, particularly those that have not responded to conventional treatments. The extended duration of administration allows ketamine to accumulate in the body at levels sufficient to modulate pain pathways more thoroughly than a brief single infusion can achieve.

Continuous infusions represent one of the most intensive forms of ketamine therapy and are typically reserved for patients with severe, debilitating pain who have exhausted other treatment options.

How They Differ from Standard Depression Infusions

The differences between continuous infusions and the standard psychiatric ketamine protocol are substantial:

The fundamental difference is one of intensity and purpose. Standard depression infusions aim to produce a rapid but temporary shift in brain chemistry that alleviates mood symptoms. Continuous infusions aim to reset dysfunctional pain signaling pathways through prolonged exposure to ketamine, a process that may require days of sustained administration.

Primary Use Cases

Complex Regional Pain Syndrome (CRPS)

CRPS — formerly known as reflex sympathetic dystrophy (RSD) — is the condition most commonly treated with continuous ketamine infusions. It is one of the best-studied indications for chronic pain treatment with ketamine. CRPS is a chronic pain condition characterized by severe, burning pain typically affecting a limb, often accompanied by swelling, changes in skin color and temperature, and extreme sensitivity to touch. It is among the most painful conditions known to medicine, and many patients with CRPS do not respond adequately to standard pain treatments.

The rationale for using prolonged ketamine infusions in CRPS is based on the role of NMDA receptors in central sensitization — the process by which the nervous system amplifies pain signals. Ketamine's mechanism for addressing this is grounded in glutamate system modulation. In CRPS, the central nervous system becomes stuck in a state of hyperexcitability, transmitting pain signals even in the absence of ongoing tissue damage. By blocking NMDA receptors for an extended period, continuous ketamine infusions may help "reset" these dysregulated pain circuits.

Clinical studies of multi-day ketamine infusions for CRPS have reported significant pain reduction in a substantial proportion of patients, with some experiencing weeks to months of relief following a single course of treatment.

Severe Neuropathic Pain

Other forms of neuropathic pain — pain caused by nerve damage or dysfunction — may also be treated with continuous ketamine infusions when other treatments have failed. This includes post-surgical neuropathic pain, diabetic neuropathy, post-herpetic neuralgia, and central pain syndromes. The NMDA receptor-blocking properties of ketamine are particularly relevant for neuropathic pain, as NMDA receptors play a central role in the development and maintenance of neuropathic pain states.

Status Migrainosus and Refractory Migraine

Status migrainosus — a severe, continuous migraine lasting more than 72 hours — and other forms of refractory migraine are increasingly being treated with multi-day ketamine infusions. Several specialized headache centers have developed protocols for inpatient ketamine infusions lasting 3 to 7 days, reporting significant improvement in patients who have not responded to standard migraine treatments.

The mechanism is thought to involve disruption of the cortical spreading depression and central sensitization processes that perpetuate chronic migraine.

Fibromyalgia and Central Sensitization Syndromes

Some pain specialists use extended ketamine infusions for fibromyalgia and related central sensitization syndromes, reasoning that the widespread pain and heightened pain sensitivity characteristic of these conditions may respond to NMDA receptor blockade. The evidence base for this application is more limited than for CRPS, but clinical experience has been sufficiently encouraging that some centers offer this as a treatment option.

Cancer Pain

In oncology settings, continuous ketamine infusions are sometimes used for cancer-related pain that has become refractory to high-dose opioids. Ketamine can help reduce opioid tolerance and may provide analgesic benefit independent of opioid pathways. These infusions are typically administered in a palliative care or inpatient oncology setting.

Typical Protocols

Continuous infusion protocols vary considerably between institutions, but common approaches include the following.

Outpatient Extended Infusions

Some protocols can be administered in an outpatient setting with close monitoring:

• Duration: 4 to 8 hours per session
• Dose: 0.1 to 0.35 mg/kg/hour
• Frequency: Daily for 3 to 5 consecutive days
• Setting: Outpatient infusion center with continuous monitoring
• Total cumulative dose: Varies, typically much higher than a single depression infusion

These protocols are sometimes described as "multi-day outpatient infusions" and are offered at specialized ketamine clinics and pain management centers. Patients return each day for their infusion and are discharged home in the evening.

Inpatient Multi-Day Infusions

For more intensive protocols, patients are admitted to a hospital:

• Duration: Continuous infusion over 3 to 7 days (24 hours per day in some protocols)
• Dose: Often starts at 0.1 to 0.2 mg/kg/hour and is titrated upward based on response and tolerability, sometimes reaching 0.3 to 0.5 mg/kg/hour or higher
• Setting: Hospital ward or monitored bed, occasionally ICU for higher-dose protocols
• Adjunctive medications: Midazolam or other sedatives are frequently co-administered to manage dissociative effects at higher doses; anti-emetics and clonidine may also be used
• Monitoring: Continuous cardiac monitoring, regular blood pressure checks, pulse oximetry, and neurological assessments

Ultra-High-Dose Protocols

Some specialized centers, particularly those treating severe CRPS, have developed protocols involving very high doses of ketamine administered under deep sedation or general anesthesia:

• Duration: 5 to 10 days
• Dose: Escalated to 3 to 7 mg/kg/hour in some protocols
• Setting: ICU with ventilator support available
• Sedation: Patients are kept deeply sedated, often requiring intubation at the highest dose levels
• Monitoring: Full ICU-level monitoring including continuous EEG in some cases

These protocols are highly specialized and are only offered at a small number of centers worldwide. They represent the most extreme end of the continuous infusion spectrum and carry correspondingly higher risks.

Inpatient vs. Outpatient Settings

The choice between inpatient and outpatient settings depends on the protocol intensity, patient factors, and institutional capabilities.

Outpatient settings are appropriate for:

• Lower-dose protocols (typically under 0.35 mg/kg/hour)
• Patients who are medically stable and have reliable support at home
• Shorter daily infusions (4-8 hours) with overnight breaks
• Centers with appropriate monitoring capabilities and trained staff

Inpatient settings are necessary for:

• Continuous 24-hour infusions
• Higher-dose protocols requiring deep sedation
• Patients with significant medical comorbidities requiring closer monitoring
• Protocols lasting longer than 5 days
• Ultra-high-dose protocols requiring ICU-level care

Evidence Base

The evidence for continuous ketamine infusions is strongest for CRPS, though the overall quality of evidence remains moderate compared to the well-studied standard depression protocol.

CRPS Evidence

Multiple studies have documented significant pain relief following multi-day ketamine infusions in CRPS patients:

• Open-label studies and case series have reported 50% or greater pain reduction in a majority of treated patients
• Some patients experience weeks to months of sustained pain relief following a single course
• Repeated courses appear to be effective, with some patients returning annually for treatment
• A small number of controlled studies have shown benefit, though large randomized trials are still lacking

Migraine Evidence

Growing evidence supports the use of continuous ketamine infusions for refractory migraine:

• Several retrospective studies from specialized headache centers have reported significant improvement in patients with status migrainosus and chronic daily headache
• Response rates of 50-75% have been reported, with some patients achieving sustained improvement
• Prospective studies are underway at several academic centers

Limitations of the Evidence

It is important to acknowledge the limitations of the current evidence base:

• Most studies are retrospective, open-label, or small case series
• Large, randomized, placebo-controlled trials of continuous ketamine infusions are few
• Standardized protocols are lacking, making it difficult to compare results across centers
• Publication bias may favor positive outcomes
• Long-term follow-up data is limited

Risks and Monitoring Considerations

Continuous ketamine infusions carry additional risks beyond those associated with standard single infusions, largely due to the higher cumulative doses and prolonged exposure.

Cardiovascular

• Sustained elevation of blood pressure and heart rate over multiple days
• Continuous cardiac monitoring is essential
• Patients with cardiovascular disease may be at increased risk

Hepatic

• Higher cumulative ketamine doses may stress liver function
• Liver function tests (LFTs) are typically monitored before, during, and after multi-day infusions
• Transient elevations in liver enzymes have been reported
• Infusions may be paused or discontinued if significant LFT elevation occurs

Urological

• Prolonged ketamine exposure carries a theoretical risk of lower urinary tract symptoms, though this is more commonly associated with chronic recreational abuse
• Patients are monitored for urinary symptoms during and after treatment
• Adequate hydration is encouraged

Neuropsychiatric

• Prolonged dissociation and disorientation over multiple days
• Vivid dreams, nightmares, or psychotomimetic symptoms
• Delirium in some cases, particularly at higher doses
• Cognitive effects during and for a period after the infusion (typically transient)
• Adjunctive sedative medications (benzodiazepines) are commonly used to manage these effects

Nausea and Other

• Prolonged nausea despite anti-emetic medications
• Loss of appetite during the infusion period
• Fatigue and weakness following multi-day infusions
• Need for IV fluid management and nutritional support during longer protocols

Cost Considerations

Continuous and multi-day ketamine infusions represent a significant financial commitment:

• Outpatient multi-day protocols — Typically $3,000 to $8,000 for a 3-5 day course
• Inpatient protocols — Hospital-based multi-day infusions can range from $10,000 to $30,000 or more, depending on the length of stay and level of care required
• Ultra-high-dose ICU protocols — May exceed $50,000 for a single course

Insurance coverage for continuous ketamine infusions is inconsistent. Some insurers will cover the hospital stay and monitoring costs for inpatient infusions while not covering the ketamine itself. Others may cover the entire treatment if it is deemed medically necessary for an approved indication. Patients should contact their insurance provider and the treating institution in advance to understand their financial obligations.

For many patients with severe CRPS or other qualifying conditions, the cost must be weighed against the potential for significant pain relief that has not been achievable through other means. Some patients find that the improved function and reduced need for other medications and treatments partially offsets the cost of periodic infusion courses.

Who May Be a Candidate

Continuous ketamine infusions are generally considered for patients who meet the following criteria:

• Severe chronic pain — Typically CRPS, severe neuropathic pain, refractory migraine, or other chronic pain conditions
• Treatment resistance — Failure of multiple standard treatments, including medications, physical therapy, nerve blocks, and other interventional procedures
• Medical clearance — Adequate cardiovascular, hepatic, and renal function to tolerate prolonged infusion
• Psychiatric stability — Absence of active psychosis, uncontrolled mania, or severe active substance use disorder
• Realistic expectations — Understanding that the treatment may provide significant relief but is unlikely to eliminate pain entirely, and that repeated courses may be necessary

Continuous ketamine infusions occupy a specialized niche in the broader landscape of ketamine therapy. For the right patients — those with severe, treatment-resistant pain conditions — they can provide meaningful relief that is not achievable through other means. However, they require specialized expertise, intensive monitoring, and a significant financial and time commitment, and should be pursued only after careful evaluation by experienced pain specialists.

References

• StatPearls: Ketamine — Comprehensive clinical reference on ketamine administration, including extended infusion protocols
• MedlinePlus: Chronic Pain — National Library of Medicine overview of chronic pain conditions and treatment strategies
• Ketamine Pharmacology: An Update — NIH review of ketamine pharmacodynamics including NMDA receptor blockade in pain pathways
• MedlinePlus: Ketamine Injection — Drug information on ketamine's anesthetic and analgesic properties