OBJECTIVES: To investigate the effects of the glucagon-like peptide-1 analog exenatide on blood glucose, lactate clearance, and hemodynamic variables in comatose, resuscitated out-of-hospital cardiac arrest patients. DESIGN: Predefined post hoc analyzes from a double-blind, randomized clinical trial. SETTING: The ICU of a tertiary heart center. PATIENTS: Consecutive sample of adult, comatose patients undergoing targeted temperature management after out-of-hospital cardiac arrest from a presumed cardiac cause, irrespective of the initial cardiac rhythm. INTERVENTIONS: Patients were randomized 1:1 to receive 6 hours and 15 minutes of infusion of either 17.4 μg of the glucagon-like peptide-1 analog exenatide (Byetta; Lilly) or placebo within 4 hours from sustained return of spontaneous circulation. The effects of exenatide were examined on the following prespecified covariates within the first 6 hours from study drug initiation: lactate level, blood glucose level, heart rate, mean arterial pressure, and combined dosage of norepinephrine and dopamine. MEASUREMENTS AND MAIN RESULTS: The population consisted of 106 patients receiving either exenatide or placebo. During the first 6 hours from study drug initiation, the levels of blood glucose and lactate decreased 17% (95% CI, 8.9-25%; p = 0.0004) and 21% (95% CI, 6.0-33%; p = 0.02) faster in patients receiving exenatide versus placebo, respectively. Exenatide increased heart rate by approximately 10 beats per minute compared to placebo (p < 0.0001). There was no effect of exenatide on other hemodynamic variables. CONCLUSIONS: In comatose out-of-hospital cardiac arrest patients, infusion with exenatide lowered blood glucose and resulted in increased clearance of lactate as well as increased heart rate. The clinical importance of these physiologic effects remains to be investigated.