Half-Life of Dexmedetomidine (Precedex)
Dexmedetomidine (Precedex) has a terminal elimination half-life of approximately 3 hours in adults, with a shorter redistribution half-life of less than 10 minutes. 1, 2
Pharmacokinetic Profile
Dexmedetomidine's pharmacokinetic profile includes:
- Onset of action: Less than 5 minutes
- Peak effects: 15 minutes
- Distribution half-life: 6-8.6 minutes
- Terminal elimination half-life: 3-3.7 hours
- Volume of distribution: 132-223 liters
- Clearance: 39.7-57.0 L/h
Factors Affecting Half-Life
Several factors can influence dexmedetomidine's half-life and clearance:
- Age: Clearance decreases with increasing age, potentially prolonging half-life in elderly patients 4
- Cardiac output: Decreased cardiac output reduces clearance 4
- Albumin levels: Low plasma albumin concentration increases volume of distribution, potentially prolonging elimination half-life 4
- Infusion duration: While pharmacokinetics remain generally linear even with prolonged infusions, context-sensitive half-time may increase with longer infusions 3
Special Populations
Pediatric Patients
- Infants have faster clearance of dexmedetomidine compared to adults 5
- This suggests a potentially shorter half-life in the pediatric population
Critical Care Patients
- Pharmacokinetics in critically ill patients receiving prolonged infusions remain generally consistent with those observed in healthy volunteers
- Mean residence time averages 3.86 hours in postoperative ICU patients 2
- The steady-state volume of distribution may be higher in critically ill patients compared to healthy volunteers 2
Clinical Implications
The relatively short half-life of dexmedetomidine has important clinical implications:
- Rapid recovery from sedation after discontinuation of short-term infusions
- Minimal respiratory depression compared to other sedatives 1
- Patients can be aroused to their baseline level of consciousness when stimulated 1
- Overdose primarily manifests as oversedation rather than significant hemodynamic instability 6
- The short redistribution half-life (6-8.6 minutes) allows for rapid resolution of oversedation from brief infusions 6
Metabolite Information
Dexmedetomidine is metabolized to H-3, a practically inactive metabolite with:
- Elimination half-life of approximately 9.1 hours
- AUC ratio of H-3 to dexmedetomidine of approximately 1.47 (range 0.29-4.4) 3
The relatively short half-life of dexmedetomidine makes it suitable for procedural sedation and short-term ICU sedation, with predictable offset of action when discontinued.