Effects of dezocine, morphine and nalbuphine on electropain threshold, temperature pain threshold and cardiac function in rats with myocardial ischemia.

Abstract

Myocardial ischemia (MI) could cause many complications, such as arrhythmia, ischemic cardiomyopathy, which could lead to angina and myocardial infarction. The clinical efficacy of dezocine, morphine and nalbuphine are becoming dominated in China market. This aim of this study was to investigate the effects of dezocine, morphine and nalbuphine on electrical pain threshold, temperature pain threshold and cardiac function in rats with MI. A rat model of MI was established by ligating the coronary artery. Rats in the model group were injected with dezocine, morphine, nalbuphine and 0.9% normal saline. The effects of the three analgesics on MI rats were evaluated by comparing the electrical pain threshold, temperature pain threshold, and cardiac function index. The electrocardiogram revealed that the model of MI was successful. The results of the electrical pain threshold and temperature pain threshold tests revealed that nalbuphine was the most sensitive after medication, followed by dezocine, and the sensitivity of morphine was the lowest. These three drugs reached its peak at two hours after administration. The analgesic effect of dezocine on electrical stimulation was the best, while nalbuphine had the best effect on temperature. The efficacy of dezocine decreased with time, while morphine basically failed at four hours after administration. The peak time of these three kinds of analgesics was selected to detect the cardiac function index in each group. Morphine had the least influence on the cardiac function index of rats, followed by nalbuphine and dezocine. These results show that the analgesic effect of nalbuphine had the earliest and best effect with the longest duration on temperature, and had less influence and higher safety in the cardiac function test of MI rats. Hence, nalbuphine is a relatively good analgesic for MI patients. The present study provides a database for the selection of analgesics in patients with MI.