Precedex (Dexmedetomidine) Half-Life
The elimination half-life of dexmedetomidine is approximately 2 hours (specifically 1.8-3.1 hours) in patients with normal liver function. 1
Specific Half-Life Values
- The terminal elimination half-life ranges from 83-159 minutes (approximately 1.4-2.7 hours) in patients with normal hepatic function 1
- A simplified half-life of 2 hours is commonly cited in clinical guidelines 2
- Research studies have reported an elimination half-life of 3.7 hours (geometric mean) in critically ill patients receiving prolonged infusions 3
Factors That Prolong Half-Life
- Elderly patients have decreased clearance and prolonged elimination half-life 4
- Hypoalbuminemia increases the volume of distribution at steady state and prolongs the context-sensitive half-time 4
- Severe hepatic dysfunction significantly impairs clearance, requiring lower doses due to prolonged drug elimination 1, 5
- Decreased cardiac output reduces dexmedetomidine clearance, leading to higher plasma concentrations 4
Context-Sensitive Half-Time Considerations
- For prolonged infusions (>24 hours), the context-sensitive half-time becomes more clinically relevant than the terminal elimination half-life 1
- The context-sensitive half-time is particularly important in elderly patients and those with hypoalbuminemia, where drug accumulation may occur during extended use 4
Clinical Implications
- Despite the relatively short half-life, dexmedetomidine demonstrates linear pharmacokinetics up to doses of 2.5 μg/kg/hour, even with prolonged infusions lasting up to 14 days 3
- The drug's inactive metabolite (H-3) has a longer half-life of 9.1 hours, though this metabolite is practically inactive and does not contribute to clinical effects 3
- No withdrawal effects (including rebound tachycardia or hypertension) have been reported upon discontinuation, even after prolonged use beyond 24 hours 6