Analgesic Dose of Ketamine
For intravenous ketamine analgesia in acute pain, administer 0.5 mg/kg as a bolus dose, which can be followed by a continuous infusion of 0.1-0.2 mg/kg/h (maximum 0.4 mg/kg/h) for sustained effect. 1
Intravenous Dosing for Acute Pain
The standard analgesic dose is 0.5 mg/kg IV bolus, which provides sub-anesthetic analgesia without dissociative effects when kept below 1 mg/kg. 1, 2, 3 This dose can be:
- Titrated to effect in the post-anesthesia care unit (PACU) or emergency department, with consideration for reduced dosing (0.25-0.5 mg/kg) when using S-ketamine due to its increased potency 1
- Repeated as needed for breakthrough pain at the same 0.5 mg/kg dose 1
- Combined with continuous infusion at 0.1-0.2 mg/kg/h (maximum 0.4 mg/kg/h) for procedures or sustained analgesia 1
Route-Specific Considerations
Intravenous Administration
- Bolus doses less than 0.35 mg/kg are considered safe without intensive monitoring requirements 1
- For patient-controlled analgesia (PCA), use 1-5 mg per bolus dose when added to opioid-based PCA systems 1
- Infusion rates of 0.5-1 mg/kg/h have been studied, though the lower end (0.1-0.2 mg/kg/h) is more commonly recommended to minimize adverse effects 1
Intramuscular Administration (Pediatrics)
- Initial dose: 4 mg/kg IM, with repeat dosing of 2-4 mg/kg allowed after 5-10 minutes if needed 1
- This route is primarily used for procedural sedation in children, not pure analgesia 1
Oral Administration (Chronic Pain)
- Starting dose: 0.5 mg/kg as a single oral dose for ketamine-naive patients, or 0.25 mg/kg for S-ketamine 4
- Typical maintenance: 100 mg/day divided into 3-4 doses, titrating upward by 40 mg/day as needed 5, 4
- Conversion from IV to oral: The daily parenteral dose can be maintained or reduced by 60-70% (using only 30-40% of the parenteral dose orally) 6
Clinical Context and Multimodal Integration
Ketamine functions optimally as part of a multimodal analgesic strategy rather than monotherapy. 2 The American College of Emergency Physicians recommends:
- Combining ketamine 0.5 mg/kg IV with acetaminophen 1000 mg IV and ketorolac 15-30 mg IV for opioid-sparing analgesia 2
- Adding dexmedetomidine 0.5-1 mcg/kg can enhance analgesic quality and reduce side effects 1, 7
- This approach reduces opioid requirements by 30-50% while minimizing respiratory depression 2
Critical Safety Parameters
Continuous monitoring is mandatory during ketamine administration, including:
- Pulse oximetry, capnography, blood pressure, heart rate, and respiratory rate 2
- Immediate availability of reversal agents (though no specific ketamine reversal exists, supportive care equipment must be ready) 2
Contraindications include:
- Uncontrolled cardiovascular disease
- Active psychosis
- Severe liver dysfunction
- Elevated intracranial or ocular pressure 1
Common Pitfalls to Avoid
Do not use ketamine doses above 1 mg/kg for analgesia alone, as this crosses into dissociative/anesthetic territory and increases adverse effects without proportional analgesic benefit. 3 The analgesic effects plateau at sub-dissociative doses.
Avoid rapid IV bolus administration, which can cause apnea; the standard 0.5 mg/kg dose should be given over several minutes rather than as a rapid push. 1
Consider co-administration of a benzodiazepine (midazolam 1-2 mg IV) when using ketamine doses at the higher end of the analgesic range to prevent emergence reactions and psychotomimetic effects, though this is less necessary at true sub-dissociative doses. 6
For chronic pain management, the evidence is weak and does not support routine use; oral ketamine should be reserved only for complex cases where other options have failed. 4 The poor safety profile and lack of robust efficacy data limit its role in this setting.