An 
opioid receptor agonist is a powerful effect 
analgesic medicine which is clinically and widely used, 
morphine is representative, and the 
medicine can effectively relieve pain of patients, particularly for pain of people after an operation and in the 
terminal cancer. However, opioids are easy to cause tolerance and 
hyperalgesia of patients, and the tolerance and the 
hyperalgesia can be easily formed within one week. Once the tolerance and the 
hyperalgesia are formed, dosage is continuously increased to continue to maintain the effect of alleviating pain, namely that organisms need a massivedose of medicines to achieve the effect of alleviating pain as the 
initial dose, but the higher 
dose can cause serious hyperalgesia, tolerance, 
constipation, 
addiction and respiratory depression. Cobra 
neurotoxin polypeptide can restrain the hyperalgesia and the tolerance of the opioids, and can also improve the treatment effects of opioids, and when the cobra 
neurotoxin polypeptide and the opioids are combined together for use, the opioids can alleviate pain at the lower 
dose and does not generate tolerance and hyperalgesia, so that the clinical technical problem that the opiods cannot be used for a long term can be solved.