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Dexmedetomidine Dexmedetomidine is approved by the FDA in December 1999 for sedation of patients in intensive care setting, not longer than 24 hours. Dexmedetomidine is manufactured and market in the United States by Abbott under the trade name of Precedex®. Precedex® come in a glass vial of 2 cc of dexmedetomidine 100 mcg/ml. The vial costs about 50-60 $ and must be dilute for infusion. The manufacturer recommend NSS as a diluent but LRS, D5W, mannitol, thiopental sodium, etomidiate, succinylcholine have been shown compatible.
As we are already known that Dexmedetomidine is a selective a2 adrenergic receptor (selectivity of a2/a1 is 1600 while clonidine a2/a1 selectivity is only 220). The effect of blackade of a2 adrengergic receptor will affect the CNS (brain and spinal cord) and the peripheral autonomic system). The major site of action in the brain is locus ceruleus. The CNS effects includes sedation, hypnosis, anxiolysis and analgesia. While the autonomic effects will result in hypotension and bradycardia.
After IV administration, 94% of drug will bind to plasma proteins, 6 % will present in free form which can enter the CNS through the blood brain barrier. The drug will be metabolized (hydrolized, d-methylination, conjugation) by the liver and then eliminated by the kidneys. The distribution half life (t1/2a) is approximately 6 minutes, elemination half life (t1/2b) about 2 hour, Vss of 118 L and Cl 39 L/h. Recommended dose by the manufacturer is slow loading infusion of 1 mcg/kg (over 10 min) and followed by maintenance infusion of 0.2-0.7 mcg/kg/hr. Dexmedetomidine has been studied extensively for sedation in the
patients who intubated and require mechanical ventilation. Currently,
there is no study in patients who recieve > 24 hr sedation. The
dexmedetomidine infusion is not necessary to discontinue prior to
extubation. -hypotension (28%) and bradycardia (7%), hypertension (16%) -withdrawal has been reported in patients who recieve dexmedetomidine chronically and stop abrubtly. -patients with hepatic or renal impairment may require reduced dose. -coadministration with anesthetics, sedatives/hypnotics, opioids will result in enhanced effects. -pregnancy category class C (no teratogenic effects observed),
it is not known whether dexmedetomdine is excreted in human milk. |
