Cephalosporins (cephalosporins) are semisynthetic antibiotics that contain cephtenes in their molecules. Once translated pioneer mycin. They belong to the β -lactam class of antibiotics, and are derivatives of 7-amino cephalosporanic acid (7-ACA) in the β -lactam class of antibiotics, so they have similar bactericidal mechanisms. The mechanism of action is the same as penicillin, but also inhibit the formation of bacterial cell wall to achieve the purpose of sterilization. A breeding period of bactericidal drugs. It has the advantages of wide antibacterial spectrum, strong antibacterial effect, resistance to penicillinase, and less allergic reaction than penicillins. Therefore, it is an important antibiotic with high efficiency, low toxicity and widely used in clinic.
Cephalosporin antibiotics can be divided into one, two, three and four generations according to their invention time and different antibacterial properties. The best-selling varieties are ceftriaxone sodium, cefazolin sodium, cefotaxime, ceftriazine, cefoperazone and cefuroxime (ester), etc.
The development history
Cephalosporin compounds were first extracted in 1948 by Italian scientist Giuseppe Brotzu from the top cephalosporin in the drains of the island of Sardinia. He found that these apex cephalosporins secrete substances that are effective against the bacterium typhi that causes typhoid. Cephalosporin C, which is stable to β -醘 aminase, has been successfully developed at The University of Oxford, but is not effective enough for clinical use. The core of cephalosporins is 7-amino cephalosporic acid (7-ACA) derived from cephalosporin C and has been shown to be similar to the core of penicillin (6-amino penicilanic acid, 6-APA). The modification of the side chain of 7-ACA resulted in a number of very useful antibiotics, the first of which was cephalosporan, which was released by Eli Lilly in 1964.
The chemical structure
Cephalosporins and penicillins belong to the same β -lactam antibiotics, but the difference is that the parent nucleus of cephalosporins is 7-amino cephalosporanic acid (7-ACA), while the parent nucleus of penicillin is 6-amino penicillanic acid. This structural difference makes the cephalosporins resistant to penicillase.
The physical and chemical properties
All kinds of cephalosporin are derivatives of cephalosporin acid, its free acid or substituted acid are organic acid, generally insoluble in water, but its potassium salt, sodium salt is easily soluble in water, so clinical application of cephalosporin injection dosage form is mainly made of sodium salt or potassium salt.
Cephalosporic acid contains an unstable β -lactam ring, which is easily hydrolyzed in the presence of water molecules. Alkali, acid and temperature increase can promote hydrolysis. Therefore, the clinical application of cephalosporin injection dosage form is mostly made of powder injection of solid dosage form.
Cephalosporins for injection are usually made into dry crystallization or powder of sodium salt and potassium salt and sealed in ampoules. This kind of powder ampoule can be stored at room temperature for 2 ~ 3 years, and should be used in time after adding injection solvent to dissolve before use.
Oral use of cephalosporins are some of the chemical stability slightly higher and can tolerate gastric acid varieties, such as cephalexin, cephalosporin and other free acid made of tablets or capsules.
The main features
Cephalosporins can be distributed in various parts of the body, so any infection of tissues and organs can be selected as long as the pathogenic bacteria are sensitive to cephalosporins. It is a fungicide that can kill bacteria in sufficient concentrations, unlike antimicrobial agents such as tetracycline, erythromycin and chloramphenicol, which in conventional doses mainly inhibit bacterial growth. So cephalosporins can be used for more serious infections.
Advantage 1: cephalosporin has a wide antibacterial spectrum, and cephalosporin has a good antibacterial effect on both partial gram-positive bacteria and gram-negative bacteria. (with a gram dyeing liquid on bacteria, bacteria dyed purple blue is positive, dyed crimson drops is negative) that is in the clinical departments such as internal medicine, surgery, obstetrics and gynecology, dermatology, most common pathogenic bacteria, cephalosporin tend to have certain antibacterial activity, so widely used in clinical.
Advantage 2: if bacteria produce some enzymes that destroy some antibacterial drugs, they can be resistant to some antibacterial drugs. For example, bacteria are resistant to penicillin. Cephalosporin is relatively stable to most of the enzymes produced by bacteria, and can replace penicillin to kill bacteria. Cephalosporin oral varieties are relatively more. This is because there are many varieties of oral into the stomach, the gastric acid of human body is difficult to destroy it, the drug effect is more stable.
Advantage 3: compared with penicillin, penicillin allergic reaction rate is higher, especially penicillin can cause anaphylactic shock and fatal. Cephalosporins, which have molecular similarities to penicillin, also produce allergic reactions, but the rate of allergic reactions is lower than that of penicillin, and the incidence of anaphylactic shock is even lower.
Because of the above characteristics, cephalosporin has a high practical value in clinical practice.