Plasma half-life is often used to monitor the concentration of drugs in blood. Plasma half-life is the time it takes for a drug in blood to drop from its highest concentration to half its concentration. By measuring the plasma half-life, we can understand the process of drug metabolism in blood, which is very important for guiding the clinical use of drugs. If a drug has a long plasma half-life, the interval between doses can be longer, either once a day or once every two or more days. If the plasma half-life is shorter, which means that the drug can be reduced to half of the normal concentration in a short time, the interval of drug administration must be shortened, which can be once every six hours or eight hours, to ensure that the drug in plasma always remains within the effective range, which can play a better therapeutic role.