Effects of bolus injection of esmolol in healthy, exercising subjects

Esmolol is an investigational ultra-short-acting beta-adrenergic blocker that has potential application in many clinical cardiology settings. The purpose of this study was to investigate the effect of a bolus dose of esmolol on heart rate, blood pressure, and PR interval in healthy, exercising male subjects. We gave a single esmolol bolus over 30 seconds to 13 men who exercised to a predetermined target heart rate. Each subject performed the exercise protocol twice, receiving a different dose between 10 and 300 mg each time. An additional eight subjects received two esmolol boluses 5 minutes apart while performing the same exercise protocol. Esmolol doses of 180 mg or greater caused a 13% to 18% decrease in heart rate, an 11% to 18% decrease in blood pressure, and a 13% to 22% prolongation of the PR interval. The median time to peak esmolol effect was 1 minute for heart rate, 2 minutes for blood pressure, and 4 minutes for PR interval. The median time required to recover 50%, 75%, and 90% of the decrement in heart rate was 8, 10, and 13 minutes, respectively. The rapid onset and disappearance of esmolol effects may make it an appealing drug in acute care settings.