Induction agent · Analgesic · Sedative · Bronchodilator
Ketamine
Indications
- RSI induction, favored in bronchospasm; reduced doses in shock
- Dissociative sedation for painful procedures, IV or IM
- Sole anesthetic for short procedures that need no muscle relaxation (label)
- Sub-dissociative analgesia and opioid sparing (off-label)
- Severe agitation, IM (off-label)
- Refractory status epilepticus or status asthmaticus by infusion (off-label)
Dosing
Ketamine drip card and mL/h converterStart: Analgesia 0.1–0.3 mg/kg/h (sub-dissociative); sedation 0.5–2 mg/kg/h
| Where | Dose |
|---|---|
| Airway and RSI | Ketamine: 1–2 mg/kg (0.5–1 in shock); bronchodilates; keeps BP |
| Seizures and neuro | Ketamine: 1 mg/kg IV or 4–5 mg/kg IM for severe agitation (EMS) |
| Other common pushes | Ketamine (analgesia): 0.1–0.3 mg/kg IV over 10 min |
On the quick cards
- Ketamine (Ketalar)EMS Field Drugs: Airway, RSI and sedation: dissociative induction, agitation and pain
- Airway and RSIPush and Emergency Meds: Induction, paralysis and post-intubation boluses
Mechanism of action
Ketamine is a non-competitive NMDA receptor antagonist. It enters open channels and binds the phencyclidine site in the pore, blocking Ca²⁺ and Na⁺ entry, so block builds with neuronal activity. Blocking NMDA receptors on inhibitory interneurons and in thalamocortical and limbic circuits dissociates the cortex from sensory input, and dorsal horn block prevents wind-up and central sensitization. Weaker actions at opioid receptors, HCN1 channels and monoamine transporters add to the effect.
Pharmacology
- CNS: dissociative anesthesia (eyes open, nystagmus, catalepsy) with analgesia and amnesia; analgesia alone at low doses; raises cerebral blood flow; emergence reactions in about 12% (label)
- Cardiovascular: raises heart rate, cardiac output and BP (10–50%, label) through central sympathetic outflow and blocked catecholamine reuptake; direct negative inotropy shows when catecholamines are depleted
- Respiratory: drive largely preserved; bronchodilates through catecholamine release, direct smooth muscle relaxation and vagal block; airway reflexes mostly kept but not protective; more secretions
- Other: raises intraocular pressure and muscle tone; nausea; repeated use can injure the bile ducts and bladder
Pharmacokinetics
| Onset | About 30 s IV; 3–4 min IM (label) |
|---|---|
| Duration | 5–10 min IV, 12–25 min IM (label); full recovery takes longer |
| Half-life | Distribution 10–15 min; elimination about 2.5 h (label) |
| Distribution | Vd about 3 L/kg; very lipid-soluble, so fast brain uptake, then redistribution |
| Protein binding | Low, about 10–50% (sources vary) |
| Metabolism | CYP2B6 and CYP3A4 to norketamine (about one-third as potent), then hydroxylation and conjugation |
| Clearance | High, about 12–20 mL/kg/min, near liver blood flow |
| Elimination | Urine, almost all as metabolites |
| Bioavailability | High IM; about 45–50% intranasal; about 20% oral (first pass) |
Chemistry
- 2-(2-chlorophenyl)-2-(methylamino)cyclohexanone, an arylcyclohexylamine related to phencyclidine
- One chiral carbon; Ketalar is racemic. S-ketamine (esketamine) has 3–4 times the NMDA affinity and potency of R-ketamine; in the US it is sold only as a nasal spray (Spravato) for depression
- pKa 7.5: just over half ionized at pH 7.4, yet lipid-soluble enough for fast brain entry
- Water-soluble hydrochloride at 10, 50 and 100 mg/mL, pH 3.5–5.5, with benzethonium chloride; dilute the 100 mg/mL strength before IV use (label)
Adverse effects and cautions
In the one-pagers
- Airway and RSIRSI drugs: Ketamine: 1–2 mg/kg: About 30 s: Raises HR, BP; bronchodilates; emergence
- Behavioral Emergencies, Agitation and AbuseSedation by cause (NASEMSO doses, BETA choice): Immediate danger: Dissociative: Ketamine 4 mg/kg IM (3-5 min), 2 mg/kg IV; airway kit open
- Asthma and COPD ExacerbationsVentilating obstructed lungs: Ketamine is a useful induction drug in asthma (bronchodilates)
- Pulmonary EmbolismSupporting the failing RV: Intubation can trigger arrest: induction drops SVR, positive pressure cuts venous return, apnea raises CO₂ and PVR. If unavoidable: norepinephrine running, expert operator, preoxygenate, reduced-dose etomidate or ketamine, VT 6 mL/kg, plateau <30, low PEEP, ECMO team aware.
- BurnsWound care, pain and daily nursing checks: Burn pain is background, breakthrough and procedural, and dressing changes hurt most. Give opioids IV during resuscitation, since subcutaneous and IM absorption is unreliable, and expect doses to climb with tolerance. Add scheduled acetaminophen, ketamine for procedures, gabapentinoids for neuropathic pain and itch, and distraction such as virtual reality
- Common EMS MedicationsPain, sedation, nausea and bleeding: Ketamine, dissociative (NMDA): Pain; severe agitation: Pain 0.25 mg/kg (max 25 mg); agitation 4 mg/kg IM: Dangerous BP rise; laryngospasm, emergence
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Sources
- FDA label: Ketalar (2026)
- PubChem: ketamine
- Gao 2016 (review)
- Casey 2025 (RSI trial)
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow your local protocols and medical direction.