First, the basic principles of clinical application of antibacterial drugs
(1) Patients with viral diseases and fever of unknown origin should not use antibiotics. Except for serious illness and suspected bacterial infection, the clinical symptoms are atypical and the pathogenic bacteria are not easy to detect, thus delaying the correct diagnosis and treatment. Upper respiratory tract infection, sore throat and angina pectoris are mostly caused by virus infection and should be treated with antiviral drugs.
(2) Choose drugs in strict accordance with indications. Antibiotics should be selected according to the results of bacterial culture and drug sensitivity test. Each antibiotic has different antibacterial spectrum and indications. Clinical diagnosis, bacteriological diagnosis and drug sensitivity test in vitro can be used as an important reference for drug selection. However, due to limited conditions or critical illness, it can also be selected according to the infection site and experience, which has poor reliability. Generally speaking, Gram-positive cocci are the most common respiratory infections. Gram-negative bacteria are common in urinary tract and biliary tract infections. Staphylococcus aureus is the most common infection in skin wounds. Drug selection should also be based on the general situation of patients, liver and kidney function, infection site, pharmacokinetic characteristics, the possibility of bacterial drug resistance, adverse reactions and price. Antibiotics can cure diseases, but they also have side effects. No antibiotic is absolutely safe without side effects. Newborns, the elderly and people with hepatic and renal insufficiency should avoid or use more toxic antibiotics, which are mainly excreted through liver metabolism and kidney. Such as streptomycin, gentamicin, kanamycin, etc., can damage the eighth cranial nerve and cause deafness. Penicillin can cause anaphylactic shock, rash and drug fever. The application of broad-spectrum antibiotics, such as tetracycline, will lead to a large number of drug-resistant bacteria in the body, thus causing new and more serious infections. Therefore, the use of antibiotics should be targeted and not abused.
(3) Antibacterial dosage. The dosage should be appropriate and the course of treatment should be sufficient. If the dose is too small, it will not only have no therapeutic effect, but also make bacteria resistant. Excessive dosage will not only cause waste, but also bring serious toxic and side effects. Too short a course of treatment is easy to make the disease relapse or turn chronic. (4) Local infections such as skin and mucous membrane: Local application of antibiotics should be avoided as far as possible, because allergic reactions and drug-resistant bacteria are prone to occur. (5) Preventive application and combined application: the indications should be strictly controlled, and the preventive application of antibacterial drugs is limited to a few cases, such as those proved to be effective by clinical practice; Combined medication must also carefully grasp the indications and weigh the advantages and disadvantages.
Second, the combined application of antibacterial drugs
(1) Significance of combined use of antibacterial drugs: The main advantages of combined use of drugs are: ① exerting the synergistic antibacterial effect of drugs and improving the curative effect; ② Delaying or reducing the emergence of drug-resistant bacteria; ③ For cases with mixed infection or unable to make bacteriological diagnosis, combined medication can expand the antibacterial scope; ④ Combined medication can reduce the dosage of a single drug, thus reducing the side effects.
Abuse of combined use of antibacterial drugs may have adverse consequences: for example, increasing the incidence of adverse reactions; It is prone to double infection; Drug-resistant strains increased more; Waste medicine; Give people a false safe infection and delay the correct treatment.
(2) Indications for combined medication: The indications for combined medication include ① severe infection with unknown pathogens; (2) Serious mixed infections, such as peritonitis after intestinal perforation, which can't be controlled by a single antibiotic, are often caused by a variety of aerobic and anaerobic bacteria; ③ Infective endocarditis or septicemia that can not be effectively controlled by single antimicrobial agents; ④ Long-term drug use of bacteria may lead to drug resistance, such as tuberculosis, chronic urinary tract infection and chronic osteomyelitis. ⑤ Reduce the toxicity of drugs, such as amphotericin B combined with flucytosine in the treatment of deep fungi, which can reduce the dosage of amphotericin B and thus reduce the toxic reaction; ⑥ Clinical infection can generally be treated by combining two drugs, and it is often unnecessary to combine three drugs or four drugs.
(3) Possible results of combined use: The combined use of two antibacterial drugs can achieve four effects: irrelevant, additive, synergistic (enhanced) and antagonistic. Antibacterials can be divided into four categories according to their functional properties: one is sterilization in reproductive period, such as penicillin and cephalosporin; The second type is static sterilization, such as aminoglycosides and polymyxin, which can kill bacteria in both static and reproductive stages; Three kinds are quick-acting bacteriostatic agents, such as tetracycline, chloramphenicol and macrolide antibiotics, and four kinds are slow-acting bacteriostatic agents, such as sulfonamides. The combination of the first and second drugs can often achieve synergy (enhancement), such as penicillin combined with streptomycin or gentamicin in the treatment of enterococcal endocarditis; Penicillin destroys the integrity of bacterial cell wall, which is beneficial for aminoglycoside antibiotics to enter the cell and play a role. The combination of the first class and the third class may have antagonistic effect. For example, penicillin is used in combination with chloramphenicol or tetracycline. Because the latter two drugs quickly inhibited the synthesis of protein, the bacteria were in a static state, and the bactericidal penicillin could not give full play to the cell wall synthesis during the breeding period, and its antibacterial activity was weakened. The combination of the second type and the third type can be enhanced or increased. The fourth class of slow-acting bacteriostatic drugs can be used in combination with the first class. For example, when treating epidemic meningitis, penicillin can be combined with sulfadiazine to improve the curative effect.
It should be pointed out that most of the above information comes from in vitro and animal experimental observation under specific conditions, which is different from clinical observation and is for reference only. The effect of combined medication can also vary with different strains and strains, and the dosage and administration sequence will also affect the effect.
Three, the application of antibacterial drugs in liver and kidney function damage
Renal dysfunction
When renal function declines, it is advisable to reduce or extend the dose of drugs mainly excreted by the kidney. Drugs that are toxic to the kidneys, such as amphotericin B, vancomycin and aminoglycosides, should be avoided. Drugs that have no or little damage to renal function can be routinely administered under normal circumstances, but the liver function must be normal.
The dosage of mild, moderate and severe decline of renal function is 2/3 ~ 1/2, 1/2 ~ 1/5 and110 respectively.
(B) the impact of liver dysfunction
Patients with hepatic insufficiency should avoid or use chloramphenicol, lincomycin, erythromycin, rifampicin and tetracycline with caution. The liver of premature infants and newborns has low detoxification function to chloramphenicol, so chloramphenicol is prohibited.