Pharmacology:
Cefalexin is the first generation cephalosporin in pharmacology. Its antibacterial spectrum is similar to that of Cefalotin, but its antibacterial activity is worse than that of Cefalotin. Except Enterococcus and methicillin resistant Staphylococcus, most strains of Streptococcus pneumoniae, hemolytic streptococcus and penicillinase producing or non penicillinase producing Staphylococcus were sensitive to this product. This product has good antibacterial effect on Neisseria, but Haemophilus influenzae has poor sensitivity to this product; this product has certain antibacterial effect on some Escherichia coli, Proteus mirabilis, Salmonella and Shigella. Other Enterobacteriaceae, Acinetobacter, Pseudomonas aeruginosa and Bacteroides fragilis were resistant to the drug. Fusobacterium and veronicus were generally sensitive to this product, while anaerobic gram positive cocci were moderately sensitive to this product.
Pharmacokinetics:
The absorption of the drug was good. The Cmax was 18 mg / L in average one hour after oral administration of 500 mg on an empty stomach. Postprandial administration prolonged the absorption and decreased the peak plasma concentration, but the absorption did not decrease. The absorption of this product can be increased in children with celiac disease and small intestinal diverticulum, and delayed and decreased in children with Crohn's disease and pulmonary cystic fibrosis. Although the gastrointestinal absorption of the elderly did not decrease, the blood concentration of the drug remained longer than that of the young. The blood elimination half-life (T1 / 2 β) of this product is 0.6-1.0 hours. The blood concentration of probenecid can be increased by taking probenecid, and the T1 / 2 β can be extended to 1.8 hours; the T1 / 2 β can be extended to 5-30 hours in renal failure; the T1 / 2 β of newborn is 6.3 hours. The average concentration in sputum was 0.32mg/l after oral administration of 500mg every 6 hours. The concentration in purulent sputum was higher. The drug concentration in the exudate was 50% of that in the blood. The product can enter the fetal blood circulation through the placenta and the amniotic fluid of the puerpera; the milk concentration of the lactating women after oral administration of 500mg is 5mg / L. About 5% of the oral dose was excreted from bile, and the concentration of the drug in bile was 1-4 times of that in blood. The binding rate of serum protein was 10% - 15%. The drug is not metabolized in the body. 80% - 90% of the dosage is excreted in the urine within 24 hours. The peak concentration of the drug in the urine can reach 2200mg / L after oral administration of 500mg. Cefalexin can be removed by hemodialysis and peritoneal dialysis.
Indication:
It is suitable for acute tonsillitis, angina, otitis media, sinusitis, bronchitis, pneumonia and other respiratory tract infections, urinary tract infections, skin and soft tissue infections caused by sensitive bacteria. It is not suitable for severe infection.
Adverse reactions:
1. Nausea, vomiting, diarrhea and abdominal discomfort are more common.
2. Skin rash, drug fever and other allergic reactions, occasionally anaphylactic shock.
3. Nervous system reactions such as dizziness, diplopia, tinnitus and convulsion.
4. Transient renal damage may occasionally occur during the application of this product.
5. Occasionally, patients had elevated serum aminotransferase and positive Coombs test. Hemolytic anemia is rare, neutropenia and pseudomembranous colitis have also been reported.
Matters needing attention:
1. Before using this product, the patient's allergic history to cephalosporins, penicillins and other drugs should be inquired in detail. The patient with allergic shock history to penicillins should not use this product. Other patients should pay attention to the possibility of cross allergic reaction between cephalosporins and penicillins, which is about 5% - 7%. It should be carefully used under close observation. In case of allergic reaction, the drug should be stopped immediately. In case of anaphylactic shock, it is necessary to rescue immediately, including keeping airway unobstructed, oxygen inhalationand glucocorticoid.
2. Patients with a history of gastrointestinal diseases, especially ulcerative colitis, localized colitis or antibiotic associated colitis (cephalosporin rarely produces pseudomembranous colitis) and renal dysfunction should use this product with caution.
3. Interference to diagnosis: direct Coombs test positive reaction and urine sugar false positive reaction (copper sulfate method) may appear when using this product; alkaline phosphatase, serum alanine aminotransferase and aspartate aminotransferase may increase in a few patients.
4. Cephalosporins for injection should be considered when the daily oral dose is more than 4G (anhydrous Cefalexin).
5. Cefalexin is mainly excreted through the kidney. The dosage of Cefalexin should be reduced in patients with renal dysfunction.
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