Dexmedetomidine

DEXMEDETOMIDINE

Mechanism of Action

Dexmedetomidine (Precedex) is a parenteralselective α₂ agonist with sedative properties. It appears to be more selective for the α₂ receptor than clonidine. At higher doses it loses its selectivity and also stimulates α₁-adrenergic receptors.

Clinical Uses

Dexmedetomidine causes dose-dependent sedation anxiolysis and some analgesia and blunts the sym-pathetic response to surgery and other stress. Most importantly, it has an opioid-sparing effect and does not significantly depress respiratory drive; excessive sedation, however, may cause airway obstruction. The drug is used for short-term (<24 h), intrave-nous sedation of mechanically ventilated patients. Discontinuation after more prolonged use can potentially cause a withdrawal phenomenon simi-lar to that of clonidine. It has also been used for intraoperative sedation and as an adjunct to general anesthetics.

Side Effects

The principal side effects are bradycardia, heart block, and hypotension. It may also cause nausea.

Dosage

The recommended initial loading dose is 1 mcg/kg intravenously over 10 min with a maintenanceinfusion rate of 0.2–0.7 mcg/kg/h. Dexmedetomi-dine has a rapid onset and terminal half-life of 2 h. The drug is metabolized in the liver and its metab-olites are eliminated in the urine. Dosage should be reduced in patients with renal insufficiency or hepatic impairment.

Drug Interactions

Caution should be used when dexmedetomidine is administered with vasodilators, cardiac depressants, and drugs that decrease heart rate. Reduced require-ments of hypnotics/anesthetic agents should prevent excessive hypotension.