Age has a very obvious effect on the effect, metabolism, dose and toxic side effects of many drugs. Firstly, the kidney volume of the elderly shrinks with age, the number of glomeruli and tubules decreases significantly, the renal plasma flow decreases, causing a significant decrease in the glomerular filtration rate, the kidney’s drug clearance ability decreases significantly, and drug accumulation can occur; secondly, the weight of the liver decreases in the elderly, the enzymatic activity of drug catabolism decreases, and the liver is unable to carry out effective oxidation, reduction and hydrolysis of drugs; thirdly, the total body fluid volume of the elderly decreases significantly, the ability of plasma protein to bind drugs decreases, and the free drug in the blood increases. Third, the total body fluid volume of the elderly is obviously reduced, the ability of plasma protein to bind drugs decreases, and the free drug in the blood increases, which makes the drug concentration in the body rise accordingly; fourth, the water and muscle tissue in the body of the elderly gradually decreases, while the proportion of fat increases relatively, which makes some lipophilic drugs easily accumulate in fat; finally, the degeneration of tissue and organ function level of the elderly inevitably reduces the body’s ability to resist diseases Finally, the degradation of tissue and organ function levels inevitably reduces the body’s ability to resist disease and increases the chance of disease, especially when multiple diseases coexist and usually require simultaneous treatment with multiple drugs, which increases the incidence of adverse drug reactions such as drug interactions and possible side effects. The pharmacokinetics of the elderly also has obvious changes, such as the tendency of atrophy of the gastric mucosa, reduced gastric acid secretion, slowed gastrointestinal peristalsis, poor blood supply to the gastrointestinal tract, which can affect the solubility of many drugs, drug absorption is slowed; the elderly liver and kidney blood flow are significantly reduced, liver inactivation function and renal clearance is reduced, drug metabolism is reduced, drug distribution volume is significantly changed, especially the reduction of renal clearance rate In general, the decrease in clearance of most drugs is basically equivalent to the decrease in renal function.