Analgesic

Analgesic is a drug that can improve pain threshold and relieve pain. It can be divided into two categories according to its intensity of action. One type is a weak analgesic, has mild analgesic efficacy, and has antipyretic and anti-inflammatory properties, and is rarely used in clinical anesthesia. The other type is a strong analgesic with strong analgesic efficacy and no antipyretic and anti-inflammatory properties, which is an important auxiliary drug in anesthesia. Mainly used in the central nervous system, also known as narcotic analgesics, which refers to morphine and morphine drugs, including natural opioid, semi-synthetic and synthetic morphine-like drugs. In addition to analgesia, these drugs are addictive and should be strictly controlled. Its role is to selectively suppress pain sensation, weaken the feeling and response of pain, and increase the pain threshold, but does not affect other sensations (tactile, light and auditory). There is no consensus on the site of action of analgesics. It is generally believed to act mainly on the hypothalamus, the limbic system, and has the effect of inhibiting spinal cord reflexes against central and peripheral paralysis. Domestic studies have found that the site of morphine analgesia may be in the parafascicular nucleus neurons. Since 1973, morphine receptors have been confirmed in the brain, and morphine-like substances can also be produced in the body, and combined with this receptor to produce an analgesic effect. This internal biomass is called endorphin. Since the distribution of receptors is roughly parallel with the distribution of endorphins, the concentration of endorphins in various parts of the brain was determined. It was found that the receptors were distributed in the limbic system and striatum structure, and the distribution of white matter and cerebellum was the least. Long-term use of morphine-like drugs can produce a feedback mechanism that morphine-like drugs occupy the receptor and inhibit endogenous morphine-like compounds. Once the morphine drug is stopped, it is easy to present "endorphin" deficiency, and there are withdrawal syndromes such as dilated pupils, sweating, tachycardia, rising body temperature, nausea, vomiting, diarrhea, dehydration, insomnia, and tremors. Signs, but do not cause death. Barbital, alcohol and other hypnotics do not alleviate withdrawal syndrome. Different narcotic analgesics have cross-resistance and addiction.