Due to the aging of the elderly, all bodily functions are declining, and their ability to dispose of drugs and their responsiveness to drugs are correspondingly reduced. In the process of medication administration, there are phenomena of coexistence of multiple diseases, multiple diseases or multiple diseases, so clinicians should pay special attention to their physiological characteristics when administering medication. The physiological characteristics of the elderly related to drug use are mainly the following: 1. Physiological changes in the digestive organs of the elderly and the impact on drug absorption. The function of the stomach wall of the elderly is reduced, and the secretion of gastric acid is 25%-35% less than that of young people. The reduction of gastric acid can make the weak acidic drugs such as phenobarbital ionization degree increased, reducing the absorption of drugs; 65 years of age or older, the reduction of cardiac output, resulting in a decrease in blood flow in the digestive tract by about 40%, also resulting in a reduction in the absorption of drugs; the elderly gastrointestinal peristalsis slowed down, the drug into the small intestine delayed, drug absorption in the small intestine slowed down, so that some drugs such as acetaminophen peak time It can also reduce the effective absorption of certain drugs metabolized in the stomach, such as levodopa, due to slow gastric emptying, and prolong the retention time of drugs in the gastrointestinal tract, increasing the stimulation of the gastrointestinal tract. 2, the effect of changes in plasma protein amount and fat on drug distribution in the elderly, and the effect of changes in fat on drug distribution. Older people have lower plasma protein, less water and more fat in the body, so the plasma protein binding rate of drugs is low, the distribution volume of water-soluble drugs is smaller while the distribution volume of fat-soluble drugs is larger, the distribution volume of some water-soluble drugs such as salicylates, ethanol, morphine, penicillin, potassium salts, etc. decreases, while the distribution volume of fat-soluble drugs such as valium, lidocaine, barbiturates, etc. increases. This causes the half-life of these fat-soluble drugs to be prolonged, which makes it easy for them to accumulate in the body and become toxic. 3. Physiological changes of liver function in the elderly and the effect on drug metabolism. The liver is the main organ of drug metabolism, and as we age, functional hepatocytes and hepatic blood flow are reduced accordingly, and hepatic microsomal enzyme activity is also relatively lower. These factors can slow down the metabolism of certain drugs, prolong the half-life, increase the blood concentration, drug effects and adverse reactions, such as aminopyrine, phenytoin sodium, barbiturate, sleeper, tetracycline and other drugs, the concentration in the blood and tissues increases, the retention time in the body is prolonged by 20% to 50%. In particular, such as Valium and other drugs in the body retention time of the elderly than young people can be extended 4-5 times. 4, the physiological changes in the function of the kidneys of the elderly and the impact on drug excretion. Most of the drugs and their metabolites are excreted by the kidneys, 65-year-old elderly renal blood flow is about 40%-50% of the young, resulting in a decrease in the glomerular filtration rate, the renal excretion of drugs easy to accumulate in the body caused by adverse reactions or poisoning. For example, the accumulation of aminoglycoside antibiotics in the body, prone to adverse reactions.