Sedative · Alpha-2 agonist
Dexmedetomidine (Precedex)
Also called Precedex
Indications
- Sedation of intubated, ventilated adults (label: up to 24 h; trials ran for days)
- Procedural sedation of non-intubated adults and children, including awake fiberoptic intubation
- Light ICU sedation: PADIS 2025 favors it over propofol when light sedation or less delirium is the goal
- Agitated delirium that blocks extubation (off-label; PADIS 2018)
- Adjunct for autonomic signs of alcohol withdrawal (off-label)
Dosing
Dexmedetomidine drip card and mL/h converterStart: 0.2–0.7 mcg/kg/h; the loading dose is often skipped
Mechanism of action
Dexmedetomidine is a highly selective α₂-adrenergic agonist (α₂:α₁ ratio 1620:1, against 220:1 for clonidine). At α₂A receptors in the locus coeruleus it activates inhibitory Gi proteins: cAMP falls, potassium channels open and hyperpolarize the neuron, and calcium entry drops, so norepinephrine release falls. Quieting the locus coeruleus engages the brain's natural sleep pathways, giving rousable sedation, and spinal α₂ receptors reduce pain transmission. It has no GABA-A activity.
Pharmacology
- CNS: rousable, cooperative sedation like non-REM sleep; little amnesia; modest opioid-sparing analgesia; not anticonvulsant and not enough alone for deep sedation
- Cardiovascular: biphasic. A load or fast bolus stimulates vascular α₂B receptors, causing brief hypertension with reflex bradycardia; central sympatholysis then lowers BP and heart rate, occasionally to sinus arrest
- Respiratory: little depression; the CO₂ response is preserved, so it can run through extubation
- Other: diuresis (diabetes insipidus is a label warning), less shivering, dry mouth, and fever that resists cooling (label)
Pharmacokinetics
| Onset | About 5–15 min IV with a loading infusion; slower without one |
|---|---|
| Context-sensitive half-time | 4 min after a 10-min infusion; 250 min after an 8-h infusion (Venn 2002) |
| Half-life | Distribution 6 min; terminal about 2 h (label), 2–4 h in ICU patients |
| Distribution | Vd at steady state about 118 L (1.3–2.5 L/kg), larger with low albumin |
| Protein binding | 94% |
| Metabolism | Liver: direct N-glucuronidation and CYP2A6 hydroxylation; metabolites inactive |
| Clearance | About 39 L/h (label); high hepatic extraction, so it falls with low cardiac output and liver disease |
| Elimination | Urine (95%) as metabolites; under 1% unchanged |
| Organ failure | Severe liver impairment halves clearance (half-life about 7 h), so reduce the dose; kidney failure leaves kinetics unchanged (label) |
| Routes | IV; sublingual film (Igalmi) for agitation in schizophrenia or bipolar disorder |
Chemistry
- (S)-4-[1-(2,3-dimethylphenyl)ethyl]-1H-imidazole: an imidazole, the active S-enantiomer of the racemic veterinary drug medetomidine
- A close relative of clonidine (an imidazoline), but about 8 times more α₂-selective and much shorter-acting
- pKa 7.1: about two-thirds un-ionized at pH 7.4 and lipophilic, hence the 6-min distribution half-life
- Water-soluble hydrochloride, preservative-free: a 4 mcg/mL premix in 0.9% sodium chloride, or a 100 mcg/mL concentrate to dilute to 4 mcg/mL
- Do not run it in the same catheter as blood or plasma; it can adsorb to natural rubber (label)
Adverse effects and cautions
In the one-pagers
- Sedation, Pain and Delirium ScalesPADIS Guideline Key Points: Propofol or dexmedetomidine over benzodiazepines (2018). 2025: dexmedetomidine over propofol in ventilated adults if light sedation or less delirium is the priority. Dexmedetomidine is not for deep sedation; consider another agent if bradycardia risk is high.
- Mental Health: Meds and CommunicationAlcohol withdrawal: risk, dosing strategy and resistance: Resistance has no agreed definition; studies use more than 40–50 mg IV diazepam in 1 h or 200 mg in 4 h (ASAM 2020). One 10 mg/kg IV phenobarbital dose added to a lorazepam protocol cut ED patients’ ICU admissions from 25% to 8% (Rosenson 2013, n = 102); ASAM keeps parenteral phenobarbital to closely monitored settings. Propofol suits patie
- After Cardiac SurgerySternal wound, mobility and ERAS Cardiac: Early ambulation and upper-extremity exercise within comfort are safe and speed recovery (ERAS/STS 2024), the basis for Keep Your Move in the Tube. ERAS Cardiac 2019 also recommends goal-directed fluid therapy and tranexamic or aminocaproic acid (Class I), chemical VTE prophylaxis once hemostasis is secure, usually from day 1 (IIa), and opioid-sparing anal
- Airway and RSIConfirmation and the first hour after intubation: Rocuronium lasts about an hour; etomidate wears off in minutes. Start analgesia (usually fentanyl) and then sedation within minutes of confirmation; ED-AWARENESS (Pappal, Ann Emerg Med 2021) linked awareness with paralysis to delayed sedation after long-acting paralytics. Once the paralytic wears off, PADIS 2018 favors light sedation (RASS −2 to +1
- Obstetric EmergenciesDrugs in pregnancy in the ICU: Propofol, opioids, dexmedetomidine: Yes: Neonatal depression near delivery
- Rhythm GallerySinus rhythms and sinus node dysfunction: Exams call under 60/min sinus bradycardia; the 2018 ACC/AHA/HRS guideline and AHA 2025 use under 50, and symptoms decide treatment. Bedside causes: vagal surges (suctioning, vomiting, straining), hypoxia, hypothermia, hypothyroidism, inferior MI, hyperkalemia, raised ICP and drugs (beta-blockers, diltiazem, digoxin, amiodarone, dexmedetomidine, propofol).
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Sources
- FDA label: Precedex (2026)
- Weerink 2017 (review)
- Venn 2002
- PubChem: dexmedetomidine
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow the order, the label and your institution's protocols.