Acetaminophen and myocardial infarction in dogs.

The hypothesis that acetaminophen can reduce necrosis during myocardial infarction was tested in male dogs. Two groups were studied: vehicle- (n=10) and acetaminophen-treated (n=10) dogs. All dogs were obtained from the same vendor, and there were no significant differences in their ages (18 +/- 2 mo), weights (24 +/- 1 kg), or housing conditions. Selected physiological data, e.g., coronary blood flow, nonspecific collateral flow, epicardial temperature, heart rate, systemic mean arterial pressure, left ventricular developed pressure, the maximal first derivative of left ventricular developed pressure, blood gases, and pH, were collected at baseline and during regional myocardial ischemia and reperfusion. There were no significant differences in coronary blood flow, nonspecific collateral flow, epicardial temperature, heart rate, systemic mean arterial pressure, or blood gases and pH between the two groups at any of the three time intervals, even though there was a trend toward improved function in the presence of acetaminophen. Infarct size, the main objective of the investigation, was markedly and significantly reduced by acetaminophen. For example, when expressed as a percentage of ventricular wet weight, infarct size was 8 +/- 1 versus 3 +/- 1%(P <0.05) in vehicle- and acetaminophen-treated hearts, respectively. When infarct size was expressed as percentage of the area at risk, it was 35 +/- 3 versus 13 +/- 2% (P <0.05) in vehicle- and acetaminophen-treated groups, respectively. When area at risk was expressed as percentage of total ventricular mass, there were no differences in the two groups. Results reveal that the recently reported cardioprotective properties of acetaminophen in vitro can now be extended to the in vivo arena. They suggest that it is necessary to add acetaminophen to the growing list of pharmaceuticals that possess cardioprotective efficacy in mammals.