Amoxicillin is a penicillin antibiotic with good antibacterial activity against Streptococcus pneumoniae, Streptococcus haemolyticus and other streptococci, non-penicillinase producing Staphylococcus, Enterococcus faecalis and other aerobic Gram-positive cocci, Escherichia coli, Methylobacterium oddum, Salmonella spp.
Amoxicillin exerts its bactericidal effect by inhibiting the synthesis of bacterial cell wall, which can cause the bacteria to rapidly become spheroid and dissolve and rupture.
Pharmacokinetics]
It is rapidly absorbed after oral administration, about 75%-90% can be absorbed from the gastrointestinal tract, and the effect of food on drug absorption is not significant. The peak blood concentration (Cmax) is 3.5~5.0mg/L and 5.5~7.5mg/L after 0.25g and 0.5g oral administration respectively, and the time to peak is 1~2 hours. The product is well distributed in most tissues and body fluids. The mean drug concentrations in sputum 2-3 hours and 6 hours after oral administration of 0.5g of this product in patients with acute exacerbation of pneumonia or chronic bronchitis were 0.52mg/L and 0.53mg/L, respectively, while the blood concentration in the same period was 11mg/L and 3.5mg/L. The drug concentration in middle ear fluid was 6.2mg/L 1-2 hours after oral administration of 1g of this product in children with chronic otitis media. The concentration in cerebrospinal fluid of patients with meningitis was 0.1~1.5mg/L 2 hours after taking 1g of this product orally, which is equivalent to 0.9%~21.1% of the blood concentration in the same period. It can pass through the placenta, and the concentration in cord blood is 1/4 to 1/3 of the maternal blood concentration, and it is also contained in trace amount in milk, sweat and tear fluid. The protein binding rate of amoxicillin is 17%-20%. The blood elimination half-recession period (t1/2b) is 1~1.3 hours. After taking the drug, about 24%~33% of the administered amount is metabolized in the liver, and 45%~68% of the administered amount is excreted in the urine with the prototype drug within 6 hours, and some of the drug is excreted via biliary tract. The serum half-life can be extended to 7 hours in patients with severe renal insufficiency. Hemodialysis can clear this product, while peritoneal dialysis has no effect on the clearance of this product.
Indications
Amoxicillin is indicated for the following infections caused by sensitive bacteria (non-β-lactamase-producing strains).
(1) Streptococcus haemolyticus, Streptococcus pneumoniae, Staphylococcus or Haemophilus influenzae caused by otitis media, sinusitis, pharyngitis, tonsillitis and other upper respiratory infections.
(2) Genitourinary tract infections caused by Escherichia coli, Aspergillus chimaera or Enterococcus faecalis.
(3) Streptococcus haemolyticus, Staphylococcus or Escherichia coli-induced skin and soft tissue infections.
(4) Lower respiratory tract infections such as acute bronchitis and pneumonia caused by Streptococcus haemolyticus, Streptococcus pneumoniae, Staphylococcus or Haemophilus influenzae
(5) Acute simple gonorrhea.
(6) This product can also be used to treat typhoid fever, typhoid carriers and leptospirosis; amoxicillin can also be used in combination with clarithromycin and lansoprazole to eradicate Helicobacter pylori from the stomach and duodenum and reduce the recurrence rate of peptic ulcer.
Dosage
Oral: Adults 0.5g once, once every 6-8 hours, not more than 4g per day; children 20-40mg/kg per day, once every 8 hours; infants under 3 months old 30mg/kg per day, once every 12 hours.
Patients with severe renal impairment need to adjust the dose, including 0.25~0.5g every 12 hours for patients with endogenous creatinine clearance of 10~30ml/min; 0.25~0.5g every 24 hours for patients with endogenous creatinine clearance less than 10ml/min.
[Adverse reactions
(1) Gastrointestinal reactions such as nausea, vomiting, diarrhea and pseudomembranous enteritis.
(2) Allergic reactions such as skin rash, drug fever and asthma.
(3) Anemia, thrombocytopenia, eosinophilia, etc.
(4) Serum aminotransferase may be mildly increased.
(5) Secondary infection caused by Candida or drug-resistant bacteria.
(6) Occasionally, central nervous system symptoms such as excitement, anxiety, insomnia, dizziness and abnormal behavior may be seen.
Contraindications
Contraindicated in patients with penicillin allergy and positive penicillin skin test.
Precautions
(1) Penicillin sodium skin test must be done before use, positive reaction is prohibited.
(2) Patients with infectious mononucleosis are prone to skin rash and should avoid using this product.
(3) Patients with a long course of treatment should check liver and kidney function and blood routine.
(4) Amoxicillin may cause false positive urine glucose test using Benedict’s or Fehling’s reagents.
(5) The following conditions should be used with caution.
(① Those with a history of allergic diseases such as asthma and cushings fever.
(2) Dose adjustment may be required in the elderly and in cases of severe renal impairment.
Pregnant women and nursing mothers
Animal reproduction tests have shown that 10 times the human dose of amoxicillin did not impair fertility or fetuses in rats and mice. However, there are not enough controlled studies in humans, and since animal reproduction tests are not fully predictive of human response, pregnant women should use this product only when necessary.
Because small amounts of amoxicillin can be secreted in breast milk, administration to lactating mothers may lead to allergy in the infant.
Drug Interactions]
(1) Propofol competitively reduces the renal tubular secretion of this product, and the simultaneous application of both may cause an increase in amoxicillin blood concentration and prolong the half-life.
(2) Chloramphenicol, macrolides, sulfonamides and tetracyclines interfere with the antibacterial effect of amoxicillin in vitro, but their clinical significance is unknown.
[Drug overdose].
In a prospective study involving 51 pediatric patients, amoxicillin administration at doses up to 250 mg/kg did not cause significant clinical symptoms. Renal insufficiency and oliguria due to amoxicillin overdose have been reported in a few patients, but the renal impairment is reversible after discontinuation of the drug.