There are many varieties of cephalosporins, when playing cephalosporin to treat bacterial infections, how long the specific interval before the second infusion, with the application of the type of cephalosporin and the patient’s renal function has a lot to do with the situation. Most of the cephalosporins have a relatively short half-life, most of them are 0.5-2 hours, and some of them will be up to 3 hours, and the half-life of ceftriaxone in the third-generation cephalosporins is relatively long, which can reach 8 hours. Half-life refers to the time it takes for the concentration of a drug in the blood to drop by half, or for the drug to decrease by half in the body. According to the different half-life, the time of the second infusion of cephalosporin is not the same, the majority of cephalosporins need to be infused 2-4 times a day, some are infused at intervals of 12 hours, some are infused at intervals of 6 hours, and some are infused at intervals of 8 hours, but ceftriaxone is infused once in a day, that is, it is infused only once in 24 hours. In addition, if the patient’s renal function is not good, it is easy to cause cephalosporins to accumulate in the body, so it is necessary to extend the interval.