What is the recommended dosing for ketamine (ketamine hydrochloride) for pain management?

Ketamine Dosing for Pain Management

For acute pain management, administer ketamine as a 0.5 mg/kg IV bolus followed by a continuous infusion of 1-2 μg/kg/min (or 0.06-0.12 mg/kg/hr), which reduces opioid requirements by approximately 22 mg morphine equivalents without increasing side effects. 1

Intravenous Dosing by Clinical Context

Perioperative Pain Management

• Intraoperative use: Administer 0.5 mg/kg as a loading dose after anesthesia induction, followed by continuous infusion at 0.125-0.25 mg/kg/hr (maximum 0.5 mg/kg/hr) 2
• Discontinue the infusion 30 minutes before the end of surgery and administer a longer-acting opioid to prevent an analgesic gap 1
• For pediatric patients, use 0.5 mg/kg as an adjunct to intraoperative opioids, with optional continuous infusion of 0.1-0.2 mg/kg/hr (maximum 0.4 mg/kg/hr) 3

Acute Pain in Emergency/ICU Settings

• Initial bolus: 1-4.5 mg/kg IV over 60 seconds for anesthesia induction; for analgesia alone, use lower doses of 0.1-0.35 mg/kg 4
• Continuous infusion: 0.5-2 mg/kg/hr (maximum 100 mg/hour) using the lowest effective dose 1
• Breakthrough pain in PACU: 0.5 mg/kg titrated to effect 3
• Low-dose ketamine at 0.3 mg/kg provides superior pain relief compared to 0.15 mg/kg when used as an adjunct to morphine, though it may cause more dysphoria and dizziness 5

Cancer-Related Neuropathic Pain

• Start with subanesthetic doses when other modalities fail, though evidence is limited 1
• For chronic neuropathic pain in advanced cancer, begin with 10 mg/day by continuous IV infusion, increasing by 10 mg/day every 4-6 hours to 50 mg/day, then by 25 mg/day every 12-24 hours until pain relief is achieved 6
• Gradual dose titration prevents psychotomimetic effects at doses below 300 mg/day without requiring prophylactic psychotropic medications 6

Oral Ketamine Dosing

Chronic Pain Management

• Starting dose: 0.5 mg/kg racemic ketamine (or 0.25 mg/kg S-ketamine) as a single oral dose 7
• Titration: Increase by the same amount if required, typically given 3-4 times daily for continuous analgesic effect 7
• Effective maintenance dose: Mean effective oral dose is approximately 2 mg/kg daily, divided into 3-4 doses 8
• When converting from parenteral to oral administration, maintain the same daily dosage initially, then adjust based on clinical effect 7
• The injection fluid can be taken orally 7

Route-Specific Considerations

Intramuscular Administration

• Dose range: 6.5-13 mg/kg IM 4
• A dose of 9-13 mg/kg produces surgical anesthesia within 3-4 minutes, lasting 12-25 minutes 4

Preparation and Dilution

• Do not inject the 100 mg/mL concentration IV without proper dilution 4
• Dilute with equal volume of Sterile Water, Normal Saline, or 5% Dextrose in Water 4
• For maintenance infusion, prepare 1 mg/mL solution by adding 10 mL of 50 mg/mL (or 5 mL of 100 mg/mL) to 500 mL of IV fluid 4
• Use immediately after dilution 4

Critical Safety Measures

Monitoring Requirements

• Continuous cardiac monitoring and pulse oximetry during ketamine infusion 1
• Regular assessment of sedation level, respiratory status, and hemodynamic parameters 1, 2
• Emergency airway equipment must be immediately available 4
• Practitioners must be able to identify and rescue patients from unintended deep sedation 2

Minimizing Adverse Effects

• Co-administer benzodiazepines to minimize psychotomimetic effects (dysphoria, nightmares, hallucinations), especially at higher doses and with prolonged use 1
• Administer an antisialagogue prior to induction to reduce salivation 4
• Administer slowly over 60 seconds when giving IV bolus; rapid administration causes respiratory depression and enhanced vasopressor response 4

Absolute Contraindications

• Uncontrolled cardiovascular disease 1, 2
• Pregnancy 1
• Active psychosis 2
• Severe liver dysfunction 2
• High intracranial or ocular pressure 2

Special Populations

Patients with Shock

• Ketamine maintains cardiovascular stability through NMDA blockade and preserved adrenal function, making it superior to propofol or dexmedetomidine 9
• Use reduced doses (start at lower end of 0.5 mg/kg IV bolus) with careful monitoring, as ketamine can suppress myocardial contractility when catecholamine reserves are depleted 9

Patients on Chronic Opioids

• Ketamine is more effective and causes fewer adverse effects in patients already receiving opioid therapy (7% failure rate vs. 36% in opioid-naive patients) 8
• Results in mean opioid sparing of 63% 8

Common Pitfalls to Avoid

• Do not continue ketamine postoperatively beyond the immediate perioperative period, as this increases hallucination risk without enhancing analgesia 2
• Do not use mixed agonist-antagonists (butorphanol, pentazocine) in combination with ketamine 3
• Monitor for genitourinary pain in patients with chronic ketamine use; consider cessation if symptoms develop 4
• Purposeless and tonic-clonic movements during ketamine anesthesia do not indicate inadequate anesthesia and do not require additional dosing 4