# Ketamine in Pain Management

Use subanesthetic ketamine selectively as an opioid-sparing analgesic for acute perioperative or severe acute pain, especially with opioid tolerance, while reserving chronic-pain infusions for carefully selected refractory cases with structured monitoring for dissociation, sympathetic effects, and longer-term toxicity.

**Clinical question:** When should clinicians use ketamine for acute or chronic pain, and how should they dose, monitor, and select patients?

Updated: 2026-08-24T16:57:06.246009+00:00

## What matters in practice
- For perioperative analgesia outside an ICU, keep an intravenous ketamine bolus at or below 0.35 mg/kg and infusion at or below 1 mg/kg/hour. [2]
- Consider perioperative ketamine when moderate-to-severe postoperative pain or opioid tolerance is anticipated; effects include lower postoperative pain, opioid use, nausea, and vomiting in aggregate evidence. [4][19]
- Avoid ketamine in severe or uncontrolled cardiovascular disease, severe liver disease, increased intracranial or intraocular pressure, pregnancy, and psychotic illness. [2]
- Chronic-pain ketamine is an off-label, higher-risk strategy for refractory disease; benefit is inconsistent and prolonged exposure raises concern for neuropsychiatric, urologic, and other adverse effects. [16][21]
- Monitor airway, breathing, circulation, hemodynamics, mental status, and emergence phenomena during parenteral ketamine administration. [4][20]

## Choose ketamine for an analgesic problem it can plausibly change

Use ketamine as an adjunct or alternative analgesic, not a default substitute for diagnosis and multimodal care.

At subanesthetic doses, ketamine antagonizes the N-methyl-D-aspartate receptor and may reduce central sensitization, a rationale most relevant to severe acute pain, opioid tolerance, opioid-induced hyperalgesia, and allodynic pain states. [4][21] In perioperative practice, prioritize it for patients expected to have moderate-to-severe postoperative pain or pre-existing opioid tolerance, where opioid-sparing is clinically valuable. [4]

For acute postoperative use, intravenous ketamine administered during surgery reduces postoperative pain, opioid consumption, nausea, and vomiting in pooled evidence. [19] Its role in trauma is less certain: ICU trials report analgesia comparable with opioids alone, but a randomized trial in severely injured patients found no significant reduction in pain scores or opioid use versus placebo and stopped for futility. [4]

For chronic pain, treat ketamine as an off-label option for selected refractory cases rather than routine long-term pharmacotherapy. It has been used for difficult-to-manage conditions including complex regional pain syndrome, but trials and protocols vary substantially, and longer-term safety data are limited. [16][21]
- Before ordering ketamine, document the analgesic target: opioid sparing, inadequate analgesia despite usual therapy, opioid tolerance, or suspected hyperalgesia/allodynia. [4]
- For chronic pain, define a measurable treatment target before infusion, such as pain intensity or functional improvement, and discontinue escalation when benefit is absent or adverse effects are limiting. Evidence from high-dose palliative titration did not show improved pain intensity and showed nearly twice the adverse-effect incidence versus comparator. [21]

*Clinical scenarios in which ketamine’s expected benefit and uncertainty differ. [4][16][19][21]*

| Clinical setting | Reason to consider ketamine | Decision-limiting issue |
| --- | --- | --- |
| Perioperative moderate-to-severe pain | Adjunctive intravenous ketamine can reduce postoperative pain and opioid use. [19] | Use non-ICU dose limits and screen contraindications. [2] |
| Opioid tolerance or hyperalgesia | NMDA antagonism may address central sensitization and opioid-related hyperalgesia while reducing opioid exposure. [4] | Monitor for dissociation, dysphoria, hypertension, and tachycardia. [4] |
| Severe traumatic injury | May provide analgesia comparable with opioid-based approaches in ICU studies. [4] | Trial results on opioid reduction and pain scores are conflicting. [4] |
| Refractory chronic pain or CRPS | Off-label use may be considered after conventional strategies have failed. [16] | Benefits are heterogeneous; repeated or prolonged therapy requires caution because of adverse-effect burden and uncertain long-term safety. [21] |

## Use conservative intravenous dosing and a monitored delivery setting

The strongest operational limits apply to perioperative intravenous use outside intensive care.

For perioperative analgesia in a non-ICU setting, do not exceed an intravenous ketamine bolus of 0.35 mg/kg or an infusion rate of 1 mg/kg/hour. [2] These are ceiling limits rather than mandatory starting doses; titrate within institutional protocols to analgesic response and adverse effects.

Do not use ketamine patient-controlled analgesia as the sole postoperative analgesic strategy on the basis of current consensus evidence. [2] Pair ketamine with procedure-appropriate multimodal analgesia and regional techniques when indicated, because ketamine is principally an opioid-sparing adjunct rather than a comprehensive postoperative pain plan. [4][19]

In the emergency department, low-dose ketamine has shown analgesic effectiveness comparable with morphine within 60 minutes, with comparable safety in a systematic review. [2] Select this approach when opioid avoidance is desirable or conventional opioid analgesia is inadequate, while ensuring capacity for hemodynamic and neurobehavioral observation. [2][4]
- Use intravenous administration when rapid titration and continuous observation are required. [2][20]
- Reassess pain, blood pressure, heart rate, mental status, and dysphoric or dissociative symptoms after dosing changes. [4][20]
- Escalate to a higher-acuity setting rather than increasing ketamine empirically when clinically important respiratory, hemodynamic, or neuropsychiatric instability develops. [20]

*Operational approach to intravenous ketamine for acute analgesia. [2][4][19][20]*

| Step | Action | Interpretation or next action |
| --- | --- | --- |
| Pre-administration | Screen for severe/uncontrolled cardiovascular disease, severe liver disease, elevated intracranial or intraocular pressure, pregnancy, and psychosis-associated psychiatric illness. [2] | If present, avoid ketamine and select another analgesic approach. [2] |
| Dose guardrail | Limit bolus to no more than 0.35 mg/kg and non-ICU infusion to no more than 1 mg/kg/hour. [2] | Do not exceed these consensus limits in a non-ICU setting. [2] |
| Monitoring | Observe airway, breathing, circulation, hemodynamics, and mental status. [4][20] | Treat clinically significant sympathomimetic or neuropsychiatric effects as dose-limiting. [4][20] |
| Response assessment | Measure pain and opioid requirements after initiation. [19] | If analgesia is inadequate without an opioid-sparing benefit, reassess the pain generator and discontinue ineffective therapy rather than continuing exposure. [21] |

## Exclude high-risk patients and monitor for dissociation and sympathetic stimulation

Adverse effects and contraindications determine whether ketamine remains an analgesic option.

Avoid ketamine in severe or uncontrolled cardiovascular disease because sympathetic stimulation can produce transient hypertension and tachycardia. [2][4] Avoid it in severe liver disease, increased intracranial pressure, increased intraocular pressure, pregnancy, and psychiatric disease associated with psychosis. [2]

The clinically important acute adverse effects are dissociation, dysphoria, delirium, hallucinations, hypertension, and tachycardia. [4][7][20] High-dose S-ketamine can cause reversible neuropsychiatric effects, including hallucinations. [7] Monitor mental status and vital signs during infusion, and reduce or stop treatment when adverse effects outweigh analgesic benefit.

Ketamine toxicity may involve neurologic, cardiovascular, psychiatric, urogenital, and abdominal manifestations; acute effects can last from 15 minutes to several hours depending on dose, route, metabolism, and individual sensitivity. [20] A patient with suspected excessive exposure requires airway, breathing, and circulation assessment rather than management based only on reported pain relief. [20]
- Avoid interpreting dissociation or euphoria as evidence of analgesic success; use a documented pain and function target. [20][21]
- For repeated chronic exposure, ask specifically about urinary frequency, dysuria, hematuria, and bladder pain; such symptoms have been reported in pain patients receiving oral ketamine. [21]
- Do not continue a chronic regimen solely because a transient infusion response occurred; longitudinal safety and durable efficacy remain key decision constraints. [21]

*Ketamine safety screen and action thresholds. [2][4][20][21]*

| Finding | Clinical concern | Action |
| --- | --- | --- |
| Severe or uncontrolled cardiovascular disease | Sympathomimetic hypertension and tachycardia. [2][4] | Avoid ketamine. [2] |
| Psychosis-associated psychiatric illness | Potential exacerbation of psychotomimetic effects. [2] | Avoid ketamine. [2] |
| Severe liver disease, elevated intracranial pressure, elevated intraocular pressure, or pregnancy | Consensus-listed contraindication or avoidance setting. [2] | Avoid ketamine. [2] |
| New delirium, dysphoria, hallucinations, or dissociation during treatment | Dose-limiting neuropsychiatric toxicity. [4][7][20] | Reduce or stop ketamine and reassess analgesic strategy. [20] |
| Frequency, hematuria, dysuria, or bladder pain with repeated use | Possible ketamine-associated urologic toxicity. [21] | Stop exposure and evaluate the urinary syndrome. [21] |

## Reserve infusion-based ketamine for refractory chronic pain with explicit stopping rules

Chronic use has less certain durability and greater cumulative safety concern than acute perioperative use.

Ketamine for chronic pain is off-label and has been applied to difficult-to-manage pain syndromes, including CRPS. [16] It can reduce hyperalgesia and allodynia in some chronic pain contexts, but individual response is variable and the therapeutic decision should follow failure or intolerance of conventional analgesic and nonpharmacologic approaches. [5][16]

Do not extrapolate a single CRPS protocol to all patients. A reported routine target in one intravenous CRPS infusion program was 150 mg/hour, or 600 mg over 4 hours, with higher doses considered only for carefully selected patients. [14] Conversely, a small study of subanesthetic S(+)-ketamine found no reduction in pain or change in thermal or mechanical detection and pain thresholds. [11] The contrast supports individualized trials with prespecified efficacy and safety endpoints rather than automatic serial infusions.

Long-term treatment decisions should weigh uncertain durable benefit against neuropsychiatric and urologic risk. In refractory cancer pain, rapid subcutaneous titration to high dose showed no difference in patient-reported pain intensity and nearly twice the incidence of adverse effects. [21] If a time-limited trial does not produce meaningful patient-specific improvement without intolerable adverse effects, stop rather than converting to maintenance ketamine. [21]
- Use chronic ketamine only in a setting able to monitor acute psychotomimetic and cardiovascular effects. [4][20]
- Before repeat treatment, reassess for new urinary symptoms and for psychiatric adverse effects that may make further exposure unfavorable. [20][21]
- Avoid claiming disease modification or prevention of chronic postsurgical pain; ketamine has been proposed for this purpose, but this is not an established indication. [16]

*Decision framework for chronic-pain ketamine. [11][14][16][21]*

| Decision point | Practical approach | Evidence constraint |
| --- | --- | --- |
| Indication | Limit consideration to refractory, difficult-to-manage pain after conventional options have not achieved acceptable control. [16] | Chronic analgesic use is off-label. [16] |
| CRPS infusion planning | Use a protocolized, monitored infusion plan; one program reported a routine target of 150 mg/hour or 600 mg over 4 hours. [14] | That target reflects a reported program practice, not a universal regimen. [14] |
| Assessing efficacy | Use prespecified pain and functional outcomes before and after a time-limited trial. [21] | Some CRPS data show no analgesic or sensory-threshold improvement. [11] |
| Repeat exposure | Continue only when benefit outweighs neuropsychiatric and urologic risk. [21] | Long-term safety data are limited, and adverse effects can be substantial. [21] |

## Build ketamine into a monitored multimodal analgesic plan

The correct next step after ketamine selection is structured delivery, reassessment, and discontinuation when its value is not demonstrable.

For acute perioperative analgesia, combine ketamine with opioid-sparing multimodal and regional strategies when appropriate to the procedure and patient. [4][19] Ketamine should be selected to reduce opioid exposure or improve otherwise inadequate analgesia, not to replace evaluation of a new pain generator, surgical complication, or evolving trauma pathology.

During an infusion, document the administered dose, pain response, opioid use, blood pressure, heart rate, and neurobehavioral adverse effects. [4][20] This record determines whether further titration remains justified within the non-ICU limits or whether treatment should be stopped because the toxicity-benefit balance has shifted. [2][20]

For chronic pain programs, require a reproducible benefit before repeat infusions and screen for cumulative adverse effects, particularly psychiatric disturbance and urinary symptoms. [20][21] A program that cannot provide monitoring and clear discontinuation criteria should not use repeated ketamine exposure as maintenance analgesia. [20][21]
- Acute goal: improve analgesia while reducing opioid requirement or opioid-related burden. [19]
- Monitoring goal: identify hemodynamic, airway, and neuropsychiatric toxicity early. [4][20]
- Chronic goal: continue only when a patient-specific benefit exceeds adverse-effect burden over repeated assessments. [21]

*Documentation elements that support safe ketamine continuation or discontinuation. [2][4][20][21]*

| Time point | Document | Decision enabled |
| --- | --- | --- |
| Before administration | Contraindication screen and baseline pain target. [2] | Whether ketamine is appropriate and what response is required. [2][21] |
| During administration | Dose, airway/breathing/circulation status, blood pressure, heart rate, and mental status. [4][20] | Whether to maintain, reduce, or stop treatment. [20] |
| After acute treatment | Pain response and opioid requirement. [19] | Whether ketamine provided meaningful opioid-sparing analgesia. [19] |
| Before repeat chronic treatment | Durability of benefit, psychiatric effects, and urinary symptoms. [20][21] | Whether cumulative risk justifies another exposure. [21] |

## References
1. Padma Gulur, M.B.B.S CV — www.fda.gov — https://www.fda.gov/media/157504/download
2. Ketamine in acute and chronic pain — rapm.bmj.com — https://rapm.bmj.com/content/rapm/48/Suppl_1/A357.full.pdf
3. Response to Dr Mion: ketamine for acute pain management — rapm.bmj.com — https://rapm.bmj.com/content/44/8/814.2
4. Regional, multimodal, and opioid-sparing strategies after trauma: a review | Trauma Surgery & Acute Care Open — tsaco.bmj.com — https://tsaco.bmj.com/content/11/Suppl_1/e002273
5. #36946 Ketamine in acute and chronic pain — rapm.bmj.com — https://rapm.bmj.com/content/48/Suppl_1/A357
6. ASRA Pain Medicine consensus practice infection control guidelines for regional anesthesia and pain medicine | Regional Anesthesia & Pain Medicine — rapm.bmj.com — https://rapm.bmj.com/content/early/2025/01/14/rapm-2024-105651
7. ketamine for acute postoperative pain in adults: study ... — bmjopen.bmj.com — https://bmjopen.bmj.com/content/11/12/e054681
8. Use of intravenous bolus doses of ketamine for acute refractory pain | BMJ Supportive & Palliative Care — spcare.bmj.com — https://spcare.bmj.com/content/2/Suppl_1/A75.3
9. Nonnarcotic Methods of Pain Management — www.nejm.org — https://www.nejm.org/doi/pdf/10.1056/NEJMra1807061
10. Translating Glutamate: From Pathophysiology to Treatment — www.science.org — https://www.science.org/doi/10.1126/scitranslmed.3002804
11. Ketamine in Refractory CRPS Patients — academic.oup.com — https://academic.oup.com/painmedicine/article-pdf/9/1/44/5289984/9-1-44.pdf
12. Systematic Review of Ketamine for Complex Regional Pain ... — academic.oup.com — https://academic.oup.com/painmedicine/article/16/5/943/2460721
13. AAPM 2016 Annual Meeting Abstracts | Pain Medicine — academic.oup.com — https://academic.oup.com/painmedicine/article/17/2/381/2460775
14. Intravenous Ketamine Infusion for Complex Regional Pain ... — academic.oup.com — https://academic.oup.com/painmedicine/article/20/2/323/4925560
15. Psychotomimetic - an overview | ScienceDirect Topics — www.sciencedirect.com — http://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/psychotomimetic
16. Ketamine for Pain Management—Side Effects & Potential Adverse Events - ScienceDirect — www.sciencedirect.com — http://www.sciencedirect.com/science/article/pii/S1524904217303831
17. Comparison of Nebulized Ketamine at Three Different ... — www.annemergmed.com — https://www.annemergmed.com/article/S0196-0644(21)00338-3/fulltext
18. Statements and Practice Parameters — www.asahq.org — https://www.asahq.org/standards-and-practice-parameters
19. Perioperative intravenous ketamine for acute postoperative ... — www.cochranelibrary.com — https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD012033.pub4/full
20. Ketamine Toxicity - StatPearls - NCBI Bookshelf — www.ncbi.nlm.nih.gov — https://www.ncbi.nlm.nih.gov/portal/utils/pageresolver.fcgi?recordid=69920e8e1a63f1308c2dd5f9
21. Ketamine for pain management - PMC — www.ncbi.nlm.nih.gov — https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6181464
22. 2007 nhamcs micro-data file documentation — ftp.cdc.gov — https://ftp.cdc.gov/pub/health_statistics/nchs/dataset_documentation/nhamcs/doc07.pdf
23. 2016 NHAMCS micro-data file documentation — ftp.cdc.gov — https://ftp.cdc.gov/pub/health_statistics/nchs/dataset_documentation/NHAMCS/doc16_ed.pdf
24. 2008 nhamcs micro-data file documentation — ftp.cdc.gov — https://ftp.cdc.gov/pub/health_statistics/nchs/dataset_documentation/nhamcs/doc08.pdf

## Editorial note

Prepared from cited clinical literature using Astra's research workflow. Verify recommendations against current guidance and patient-specific factors.