Amoxicillin is a semi-synthetic broad-spectrum penicillin antibiotic. Its antimicrobial spectrum and activity are essentially identical to ampicillin, but it exhibits superior acid resistance and delivers stronger, faster bactericidal effects. However, it is contraindicated for meningitis treatment. Its half-life is approximately 61.3 minutes.Amoxicillin is stable under acidic conditions, achieving 90% gastrointestinal absorption. It is absorbed more rapidly and completely than ampicillin. While its efficacy against Shigella is inferior to ampicillin, its effects on other pathogens are comparable.
【Actions of Amoxicillin】
Amoxicillin exhibits potent bactericidal activity and strong cell wall penetration.Following oral administration, the lactam ring in the drug molecule undergoes immediate hydrolysis to form a peptide bond. This rapidly binds to and inactivates bacterial transpeptidase, disrupting the sole pathway for bacterial cell wall synthesis via glycopeptide formation. Consequently, bacterial cells rapidly deform into spherical bodies before rupturing and lysing. Ultimately, the loss of cell wall integrity leads to uncontrolled water influx, causing the cells to swell and rupture.They exhibit potent bacteriostatic and bactericidal effects against most pathogenic Gram-negative and Gram-positive bacteria (including cocci and bacilli). Specifically effective against:as well as aerobic Gram-negative bacteria such as non-β-lactamase-producing strains of Escherichia coli, Proteus mirabilis, Salmonella spp., Haemophilus influenzae, Neisseria gonorrhoeae, and Helicobacter pylori. Hemodialysis removes some of the drug, but peritoneal dialysis does not eliminate this product.
Susceptible organisms:Group A, B, C, F, G, and ungrouped streptococci; Listeria monocytogenes; Corynebacterium diphtheriae; Neisseria meningitidis; Bordetella pertussis; Clostridium perfringens; Propionibacterium; Peptostreptococcus; Streptococcus bovis; Salmonella; Bacillus; Actinomyces; Leptospira; Treponema pallidum.
Unstable Susceptible Bacteria: Penicillin-susceptible or -resistant Streptococcus pneumoniae, Enterococcus faecalis, Escherichia coli, Proteus mirabilis, Shigella spp., Vibrio cholerae, Haemophilus influenzae, Neisseria gonorrhoeae, Clostridium spp.
Resistant bacteria: Staphylococcus, Corynebacterium, Klebsiella pneumoniae, Klebsiella acidopila, Proteus vulgaris, Pseudomonas, Acinetobacter, Campylobacter, Veillonella, Mycoplasma, Rickettsia, Legionella, Bacillus, Bacteroides fragilis.
Toxicology: Not yet determined.
Amoxicillin provides satisfactory efficacy in treating typhoid fever, other Salmonella infections, and typhoid carriers.It also demonstrates good efficacy against urinary tract infections caused by susceptible bacterial strains that do not produce β-lactamase. For patients with lower urinary tract infections and non-enzyme-producing Neisseria gonorrhoeae urethritis or cervicitis, a single oral dose of 3 g achieves satisfactory results.Indications include ear, nose, and throat infections; respiratory tract infections; and skin and soft tissue infections caused by Streptococcus pneumoniae, penicillinase-negative Staphylococcus aureus, hemolytic streptococci, and beta-lactamase-negative Haemophilus influenzae. Amoxicillin is also indicated for leptospirosis.This product is also indicated for urinary tract and genital infections caused by susceptible Escherichia coli, Proteus mirabilis, and Enterococcus faecalis. Combination therapy with clarithromycin and lansoprazole demonstrates good efficacy against Helicobacter pylori infection.
Amoxicillin is indicated for infections caused by susceptible bacteria (non-β-lactamase producing strains), including:
(1) Upper respiratory tract infections such as otitis media, sinusitis, pharyngitis, and tonsillitis caused by Streptococcus pyogenes, Streptococcus pneumoniae, Staphylococcus aureus, or Haemophilus influenzae
(2) Urinary tract infections caused by Escherichia coli, Proteus mirabilis, or Enterococcus faecalis
(3) Skin and soft tissue infections caused by Streptococcus pyogenes, Staphylococcus aureus, or Escherichia coli
(4) Lower respiratory tract infections such as acute bronchitis and pneumonia caused by Streptococcus pyogenes, Streptococcus pneumoniae, Staphylococcus aureus, or Haemophilus influenzae
(5) Acute uncomplicated gonorrhea
(6) May be used to treat typhoid fever, other Salmonella infections, typhoid carriers, and leptospirosis; Amoxicillin may also be used in triple therapy with clarithromycin and lansoprazole to eradicate Helicobacter pylori in the stomach and duodenum, reducing the recurrence rate of peptic ulcers.
【Adverse Reactions】
The incidence of adverse reactions with clinical use of amoxicillin is approximately 5-6%, with discontinuation due to reactions occurring in about 2% of cases. Major adverse reactions include:
1. Allergic reactions may manifest as drug fever, urticaria, rash, and asthma, particularly in patients with infectious mononucleosis. Anaphylactic shock is rare.
2. Gastrointestinal symptoms: Commonly include diarrhea, nausea, and vomiting. Occasional gastrointestinal reactions such as pseudomembranous colitis may occur.
4. Cutaneous and mucosal reactions: Occasional maculopapular eruptions, exudative erythema multiforme, Lyell's syndrome, and exfoliative dermatitis.
5. Hepatic and renal dysfunction: Mild elevations in serum aminotransferases and acute interstitial nephritis have been reported in a small number of patients.
6. Other central nervous system symptoms include agitation, anxiety, insomnia, dizziness, and behavioral abnormalities. Long-term use may lead to superinfections caused by Candida or resistant bacteria.
7. Large intravenous doses may cause convulsions and eosinophilia.
【Contraindications】
National health authorities mandate a penicillin skin test prior to amoxicillin administration. Individuals with positive reactions must not use this drug. Additionally, penicillin sodium, penicillin potassium, and other penicillin-class antibiotics require skin testing before use.If skin testing is inconvenient, take one-third of a tablet first. If no adverse reactions occur within one hour, proceed with normal dosage. Seek immediate medical attention if discomfort arises. 1. Individuals allergic to one penicillin may also be allergic to others, or to penicillamine or cephalosporins. A penicillin skin test is mandatory before use; those with positive reactions must not take it.
2. Contraindicated in patients with infectious mononucleosis, lymphocytic leukemia, cytomegalovirus infection, or lymphoma.
3. Use with caution in patients with a history of allergic conditions such as asthma, eczema, hay fever, or urticaria; or herpes virus infections, especially those with infectious mononucleosis (which may increase the risk of adverse skin reactions).
4. False-positive reactions may occur when measuring urinary glucose using copper sulfate tablets (R) or Fehling's solution. In rare cases, serum transaminase elevation, eosinophilia, and leukopenia may develop after administration.In late pregnancy, administration may reduce plasma-bound estrogen concentrations but does not affect free estrogen or progesterone levels. This product is excreted in breast milk; use by nursing mothers may sensitize infants.
Amoxicillin is available in multiple formulations, including injections, capsules, tablets, and granules. Regardless of the formulation, strict storage conditions are required: protect from light, keep tightly sealed, and store in a cool, dark, dry place. Even under optimal storage, amoxicillin may undergo chemical changes such as decomposition and polymerization during storage, potentially forming new allergenic substances.This degradation accelerates during hot, humid seasons. Additionally, amoxicillin is contraindicated for co-storage with aminoglycosides (e.g., gentamicin, kanamycin), ciprofloxacin, or pefloxacin, and must not be combined in the same container.Amoxicillin capsules must be used strictly as prescribed by a physician. Self-administration as a household medicine is both reckless and dangerous. If allergic reactions like rashes or severe gastrointestinal adverse effects such as diarrhea and vomiting occur during amoxicillin use, discontinue the medication immediately.