NMDA-receptor antagonist, dissociative anaestheticCONTROLLED SUBSTANCETHREE DISTINCT DOSE LEVELSRECOMMENDED IN SHOCK

Ketamine

Ketalar · Ketanest · Ketamin Abcur

The only anaesthetic that both sedates and stabilises the circulation — the indirect sympathetic stimulation makes ketamine the first choice for induction in the bleeding, septic, or otherwise preload-dependent patient, and the bronchodilation makes it valuable in life-threatening asthma. Respiratory drive and laryngeal reflexes are largely preserved, which is an explanation but never a guarantee. The key practical distinction is between the three dose levels: analgesia, procedural sedation, and induction are different drugs in the same ampoule.

BOXED WARNING

Analgesic dose and induction dose differ tenfold — a mix-up causes unintended dissociation, apnoea, and an unprotected airway. Always give ketamine where ventilation equipment is immediately to hand.

Dosing in adults

By indicationuppdaterad 2026-08-22

Indication	Regimen	Comment
Analgesia, sub-dissociative dose	0,1–0,3 mg/kg iv slowly over 5–10 minutes	rapid injection causes dysphoria — dilute and give by pump
Procedural sedation	1 mg/kg iv, alternatively 4 mg/kg im	the im route when iv access is not available, in children, and in agitated patients
Induction at RSI	1–2 mg/kg iv, 1 mg/kg in severe shock	in the catecholamine-depleted patient blood pressure may still fall
Severe asthma or status asthmaticus	0,5–1 mg/kg iv, then 0,5–1 mg/kg per hour	bronchodilating; added when inhaled treatment is insufficient
Continuous pain infusion	0,1–0,3 mg/kg per hour	opioid-sparing in severe or opioid-tolerant pain

Renal impairment

No established dose adjustment. The metabolite norketamine is excreted renally and may accumulate with prolonged infusion and severe renal impairment.

Hepatic impairment

Metabolised via CYP3A4 and CYP2B6. Reduce dose and extend intervals in severe hepatic failure.

Children

Procedural sedation 1–1,5 mg/kg iv or 4 mg/kg im. Children experience emergence reactions less often than adults; laryngospasm is uncommon but the most serious risk.

Pitfall

The old contraindication in raised intracranial pressure does not hold: ketamine does not lower cerebral perfusion pressure, and in concurrent shock it is the blood pressure fall after propofol that injures the brain. The remaining caution applies to untreated severe hypertension, recent myocardial infarction, and aortic dissection, where sympathetic stimulation is unwanted.

Pharmacokinetics

ONSET: 30–60 s iv · 3–5 min im
DURATION: 5–15 min iv · 15–30 min im
BIOAVAIL.: 93 % im · 20–25 % oral
Vd: 2–3 l/kg
t½: 2–3 hours
PROTEIN BINDING: 25 %
METABOLISM: CYP3A4 and CYP2B6 to active norketamine
EXCRETION: Renal as metabolites

Adverse effects by frequency

≥ 10 %

Blood pressure and heart rate rise, nystagmus, hypersalivation, nausea

1–10 %

Emergence reactions with vivid dreams and agitation, dysphoria, diplopia, increased muscle tone

< 1 %

Laryngospasm, apnoea with rapid injection, tachyarrhythmia, ketamine-induced cystitis with misuse

Monitoring schedule

Breathing pattern and saturation: continuously during and after the dose
Blood pressure and pulse: before the dose and every 5 minutes during sedation
Secretions in the airway: continuously — suction available, anticholinergic if needed
Emergence course: calm environment, minimal stimulation until the patient is oriented

Interaction burden

14clinically significant

0 contraindicated · 5 major · 9 moderate. Benzodiazepines and opioids enhance sedation and can abolish the preserved respiratory drive. CYP3A4 inhibitors prolong the effect. Midazolam 1–2 mg iv attenuates emergence reactions but is best given when they occur, not routinely to all patients.

Formulation & cost

Injection solution 10 mg/ml: for iv bolus and infusion
Injection solution 50 mg/ml: for intramuscular dose, low volume
Esketamine (Ketanest) 5 and 25 mg/ml: approximately twice the potency — halve the dose