2003B06 List the potential clinical uses of an alpha-2 adrenoceptor agonist
and outline the limitations of clonidine for each.

 

CNS:

Premedication

·      Slow onset (30 mins)

·      Long duration (3-7 hours)

·      Variable duration (CYP2D6 polymorphism)

·      No amnesia

General anaesthesia

·      Partial agonist -> ceiling effect, insufficient as sole agent

·      Prolonged hypotension

·      Delayed emergence

Systemic analgesia

·      Sedation unwanted

·      Rebound agitation and hypertension with prolonged use

o   Requires weaning

Neuraxial analgesia

·      Prolonged blockade -> inability to monitor motor function

 

CVS:

Reflex suppressant

·      Prolonged effect may be unwanted

o   Laryngoscopy

o   Surgery

·      Unable to titrate – bolus cf. infusion

Myocardial ischaemia

·      Hypotension impairs myocardial oxygen supply

Opioid withdrawal

·      Does not prevent psychological craving

Essential hypertension

·      α2 adrenoceptor upregulation – not for prolonged use

 

 

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