Pharmacological action

Amoxicillin is a broad spectrum antibiotic belonging to the group of semisynthetic penicillins. Like other penicillin antibiotics, Amoxicillin inhibits the synthesis of bacterial cell wall.

Amoxicillin exerts bactericidal action and is active against Gram-positive and gram-negative cocci such as Neisseria meningitidis, N. Gonorrhoeae, Gram-negative bacilli (Escherichia coli, Chlamydia, Bordetella pertussis, Haemophilus influenzae, Salmonella and others).

Amoxicillin is active against all microorganisms sensitive to penicillin G such as Corynebacterium, Bacillus anthracis, Streptobacilli, Listeria and others.

Amoxicillin is not effective against microorganisms, producing beta-lactamase. It is an acid-resistant substance and therefore it is effective in oral administration.

Indications

Amoxicillin is used to treat becterial infections caused by sensitive to it microorganisms. It is indicated for the treatment:

  • Infections of the respiratory tract including otitis media, tonsillitis, sinusitis and pharyngitis
  • Infections of the lower respiratory tract such as bronchitis, pneumonia, lung abscesses, pertussis
  • Infections of the urinary tract
  • Chronic and acute pyelonephritis, pyelitis, prostatitis, epididymitis;
  • Cystitis, urethritis, asymptomatic bacteriuria during pregnancy;
  • Gynecological infections
  • Infections of GI (gastrointestinal)  tract including Typhoid fever, especially complicated by septicemia, Shigellosis Biliary infections such as cholangitis, cholecystitis
  • Infections of skin and soft tissues.
    Leptospirosis.
    Acute and latent listeriosis.
    Lyme disease (Lyme disease)

Amoxicillin is used in combination with Proton pump inhibitors to treat gastritis and duodenal ulcers accompanied by Helicobacter pylori.

  • If the parenteral therapy is not required, Amoxicillin can be prescribed in the following conditions:
  • Short-term (24 – 48 hours) prophylactic therapy during surgery
  • Infective endocarditis, such as enterococcal infections
  • Bacterial meningitis
  • Septicemia caused by pathogens susceptible to amoxicillin.

Contraindications:

Amoxicillin is contraindicated for use in the following conditions:
Hypersensitivity to penicillin antibiotics;

Infectious mononucleosis, lymphatic leukemia (increased risk of side effects).
Patients with hypersensitivity to cephalosporins, carbapenems should consider the possibility of cross-allergy.
Amoxicillin should not be prescribed for patients with severe diarrhea or vomiting because of poor absorbtion.

Amoxicillin should not be used for the treatment of viral infections.

Use during pregnancy and lactation:
Use of the drug to pregnant women is possible only when benefits for mother overweights possible risk  to the child.

Amoxicillin passes into breast milk. It is not reccomeded to breasfeed while taking this medication.

Side effects:
Amoxicillin is generally well tolerated and side effect usually occurr in patients with hypersensitivity.

In some cases Amoxicillin may cause the following side effects: hives,  angioedema, erythema, rhinitis, conjunctivitis, joint pain, interstitial nephritis, eosinophilia. In very rare cases Amoxicillin may cause anaphylactic shock, erytherma multiforme, dermatitis

Amoxicillin is a also associated with: headache, fatigue, glossitis, stomatitis, hematological disorders such as thrombocytopenia, agranulocytosis, leukopenia.

Possible gastrointestinal disorders include: diarrhea, nausea, vomiting, stomach pain.
In very rare cases Amoxicillin may cause superinfections (particularly in patients with chronic diseases and reduced resistance of the organism), dysbiosis, candidiasis.

Drug interactions

There is no data on the incompatibility of Amoxicillin and other drugs.
Penicillins such as amoxicillin have an impact only on reproducing organisms, so they should not be combined with bacteriostatic antibiotics, such as tetracycline and chloramphenicol. In the presence of positive sensitivity tests Amoxicillin can be used in combination with other bactericidal antibiotics (cephalosporins, aminoglycosides). The antibacterial activity against Helicobacter pylori is increased in combination with metronidazole.

The simultaneous use of amoxicillin and allopurinol increases the possibility of skin rash. The mechanism of this phenomenon is still not understood.

Probenecid, sulfinpyrazone, acetylsalicylic acid, indomethacin, oxyphenbutazone, phenylbutazone and other drugs suppress the tubular secretion of Amoxicillin. Concomitant use of probenecid leads to a prolonged increase in the concentration of the drug in the blood at the expense of his removal by the kidneys. In contrast, tissue distribution and diffusion of amoxicillin may be reduced under the influence of probenecid.

In rare cases, Amoxicillin reduces  effectiveness of oral contraceptives.

Amoxicillin reduces clearance and increases the toxicity of methotrexate, enhances the absorption of digoxin. Simultaneous treatment with antacids reduces the absorption of amoxicillin.