Connexin 43 is located in the cardiomyocyte sarcolemma and in the mitochondrial membrane. Sarcolemmal connexin 43 contributes to the spread of myocardial ischemia/reperfusion injury, whereas mitochondrial connexin 43 contributes to cardioprotection. We have now investigated the antiarrhythmic dipeptide ZP1609 (danegaptide), which is an analog of the connexin 43 targeting antiarrhythmic peptide rotigaptide (ZP123), in an established and clinically relevant experimental model of ischemia/reperfusion in pigs. Pigs were subjected to 60 min coronary occlusion and 3 h reperfusion. ZP1609 (n = 10) was given 10 min prior to reperfusion (75 μg/kg b.w. bolus i.v. + 57 μg/kg/min i.v. infusion for 3 h). Immediate full reperfusion (IFR, n = 9) served as control. Ischemic postconditioning (PoCo, n = 9; 1 min LAD reocclusion after 1 min reperfusion; four repetitions) was used as a positive control of cardioprotection. Infarct size (TTC) was determined as the end point of cardioprotection. Systemic hemodynamics and regional myocardial blood flow during ischemia were not different between groups. PoCo and ZP1609 reduced infarct size vs. IFR (IFR, 46 ± 4 % of area at risk; mean ± SEM; PoCo, 31 ± 4 %; ZP1609, 25 ± 5 %; both p < 0.05 vs. IFR; ANOVA). There were only few arrhythmias during reperfusion such that no antiarrhythmic action of ZP1609 was observed. ZP1609 when given before reperfusion reduces infarct size to a similar extent as ischemic postconditioning. Further studies are necessary to define the mechanism/action of ZP1609 on connexin 43 in cardiomyocytes.