Ischemic pain relief in patients with acute myocardial infarction by intravenous atenolol
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Pain relief in acute myocardial infarction (AMI) by the beta-adrenoceptor antagonist, atenolol, was demonstrated by three separate studies. First, 18 patients were randomized to double-blind intravenous atenolol (5 mg) or saline immediately after admission, followed by oral atenolol (50 mg) or placebo 10 minutes later. In patients receiving atenolol, pain relief coincided with reduction in heart rate (HR), systolic blood pressure (SBP), and HR X SBP product (p less than 0.05); however, pain and these parameters were unchanged by placebo. The degree of pain relief was related to the reduction in cardiac work achieved (r = 0.725; p less than 0.001). A second open study involving 22 patients receiving intravenous atenolol (5 to 15 mg) early after AMI showed ischemic pain relief in 17 patients. They achieved a more significant reduction in HR X SBP product than those whose pain remained unchanged (p = 0.004). Finally, a retrospective study of 163 patients randomized to either atenolol or no beta blockade early after AMI revealed that patients receiving atenolol needed less opiate analgesia after admission (p less than 0.001). The safety of this therapy was illustrated by a decreased incidence of left heart failure and atrial fibrillation and no tendency to second- and third-degree heart block.