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Medical Therapy - Alpha-2 Adrenergic Agonists

In the 2007 ACC/AHA guidelines, this class of drug received a llb recommendation; that is, the usefulness is less well established by evidence/opinion.

A meta-analysis was published that revealed a reduction in the incidence of post operative ischemia and myocardial infarction in patients on alpha-2 agonists (25).Since that publication, a double blind RCT using trans-dermal clonidine also showed a decreased incidence of postoperative MI and death.(18). Presently, there are over 2000 patients who have received alpha-2 drugs in clinical trials. The results of these studies have showed a 40% reduction in perioperative cardiac events although he data for death is less clear.

Clonidine, the oldest and cheapest, appears to have the best results. It has both sedative and analgesic properties, reducing morphine requirements when administered intravenously or centrally(19). In addition, the incidence and severity of post-operative nausea and vomiting is decreased. The main side effects include hypotension and bradycardia but these occur in the same frequency as that seen with beta-blockade. An additional advantage of clonidine is that the transdermal formulation is well suited for post-operative administration. Unfortunately, in Canada, it is only available in an oral formulation.

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