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DEXMEDETOMIDINE. www.anaesthesia.co.in. email: anaesthesia.co.in@gmail.com. Medetomidine 4(5)-1-2-3-dimethyl phenyl [ethyl] imidazole Prototype of novel superselective alpha2 agonists highly selective, specific, potent alpha 2 - adrenergic agonist (1,620:1 alpha2 to 1) Dexmedetomidine -
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DEXMEDETOMIDINE www.anaesthesia.co.in email: anaesthesia.co.in@gmail.com
Medetomidine • 4(5)-1-2-3-dimethyl phenyl [ethyl] imidazole • Prototype of novel superselective alpha2 agonists • highly selective, specific, potent alpha2- adrenergic agonist (1,620:1 alpha2 to 1) Dexmedetomidine- • D-enantiomer of this racemate • Full agonist at alpha2C and partial at alpha2A and 2B receptors Atipamazole – a specific & selective alpha2 receptor antagonist, rapidly & effectively reverses sedative and cardiovascular effects of i.v. dexmedetomidine
Mechanism of action: - similar to clonidine Pharmacokinetics • Profile- more favourable for perioperative use • Et1/2: 2-3 hrs (clonidine:6-10hrs) • Highly protein bound >90% (clonidine:20-40%) • Extensive hepatic metabolism • Weak inhibitory effects on cytochrome p450 enzyme systems that might manifest as increased plasma conc. of opioids administered during anaesthesia Pharmacodynamics • similar to clonidine
USES 1. Pre-anaesthetic medication • Attenuates hemodynamic responses to tracheal intubation • Decreases plasma catecholamine conc. during anaesthesia • Decreases perioperative requirements for inhaled anaesthetics & opioids 2. Analgesia • High doses (loading 1µg/kg followed by 5-10µg/kg/hr) produces total i.v. anaesthesia without associated depression of ventilation or can be added to lignocaine in dose 0.5µg/kg - potential anaesthetic technique for patients with difficult upper airway
3. Attenuation of emergence syndrome • Hyperdynamic state seen after emergence from general anaesthesia • Improve performance of several cognitive tasks which rely on the prefrontal cortex( PFC) - Thus, value in disorders associated with enhanced startle responses and sensorimotor gating deficits eg. Schizophrenia Attention deficit hyperactivity disorder Post-traumatic stress disorder
4. Shivering • Useful in treatment 5. Post-operative sedation • Infusion (200-700µg/kg/hr) is useful for postoperative critical care patients in ICU, especially when mechanical ventilation via tracheal tube is necessary • In contrast to BZD and other sedatives, dexmedetomidine treated patients are adequately sedated yet, arousable and responsive.