What is the recommended dosing of ketamine (Ketamine) for pain management in adults?

Ketamine Dosing for Pain Management in Adults

For pain management in adults, ketamine should be administered at a dose of 0.1-0.5 mg/kg IV, with lower doses (<0.3 mg/kg) being as effective as higher doses while potentially causing fewer side effects. 1

Dosing Guidelines by Route of Administration

Intravenous Administration

• Initial dosing: 0.1-0.5 mg/kg IV 2, 1
• Infusion rate: Slow infusion over 15 minutes rather than IV push (reduces psychoperceptual side effects) 3
• Continuous infusion: 0.1-0.5 mg/kg/hour for maintenance 2, 4
• Maximum perioperative dose: 0.5 mg/kg/h after anesthesia induction 5

Oral Administration

• Starting dose: 0.5 mg/kg racemic ketamine or 0.25 mg/kg S-ketamine as a single oral dose 6
• Frequency: Usually given 3-4 times daily for continuous analgesic effect 6
• Titration: Increase by the same amount (0.5 mg/kg) if required, based on clinical response 6

Intramuscular Administration

• Dosage range: 6.5-13 mg/kg 4
• Typical dose: 10 mg/kg produces 12-25 minutes of surgical anesthesia 4

Clinical Applications

Acute Pain Management

• Perioperative pain: Maximum 0.5 mg/kg/h after anesthesia induction, with continuous infusion of 0.125-0.25 mg/kg/h (stopped 30 minutes before end of surgery) 5
• Emergency department: Low-dose ketamine (<0.3 mg/kg) is as effective as higher doses (≥0.3 mg/kg) with similar side effect profiles 1

Chronic Pain Management

• Neuropathic pain: Consider ketamine for patients with refractory chronic pain, especially with neuropathic components 2
• Cancer pain: Limited data available regarding efficacy as an adjuvant to opioids 5
• Opioid-tolerant patients: Particularly beneficial for patients taking long-term opioids or with opioid addiction 2

Special Considerations

Side Effect Management

• Psychotomimetic effects: Consider prophylactic use of haloperidol or benzodiazepines to minimize psychotomimetic side effects 7
• Administration technique: Slow infusion (15 minutes) significantly reduces moderate-to-severe psychoperceptual side effects compared to IV push (1 minute) 3
• Monitoring: Blood pressure monitoring is essential due to potential transient increases 2

Precautions

• Contraindications: Use with caution in patients with uncontrolled cardiovascular disease, pregnancy, active psychosis, severe liver dysfunction, and high intracranial or ocular pressure 2
• Abuse potential: Consider risk of abuse, especially with domiciliary treatment 2, 8

Efficacy Metrics

• Pain reduction: Can reduce pain scores by at least 4 of 10 in most patients with severe pain 7
• Opioid-sparing effect: Can reduce morphine consumption by approximately 15 mg in 24 hours 2
• Opioid dose reduction: Median opioid dose reduction of 25% when starting ketamine 7

Practical Administration Tips

• Dilution for IV use: To prepare a 1 mg/mL solution, add 10 mL (from 50 mg/mL vial) or 5 mL (from 100 mg/mL vial) to 500 mL of Dextrose 5% or Normal Saline 4
• For oral use: The injection fluid can be taken orally 6
• Switching routes: When switching from parenteral to oral administration, the daily dosage can initially be kept equal 6

Remember that ketamine's role in pain management continues to evolve, with most evidence supporting its use as an adjunctive therapy rather than monotherapy, particularly for patients with refractory pain or those who are opioid-tolerant.