Amoxicillin Prescribing Information: Method of Use, Action, Side Effects

Amoxicillin is a medication that is commonly used, either alone or in combination with clavulanic acid, to treat a variety of bacterial infections. It is particularly effective in combating infections of the upper and lower respiratory tract, as well as those affecting the middle ear and paranasal sinuses. In addition, amoxicillin is useful in treating infections of the urinary tract, genital system (including gonorrhea), skin and soft tissue infections, intra-cavity infections, abdominal disease, Lyme disease, sepsis, oral infections in dentistry and for the prevention of endocarditis. When used in combination therapy with other drugs, amoxicillin is effective in eradicating Helicobacter pylori in the presence of peptic ulcer disease.

Amoxicillin (Amoxil) Packs

Amoxicillin Action

Amoxicillin is a medication that exhibits bactericidal properties. Its mechanism of action involves inhibiting the synthesis of the bacterial cell wall, which effectively hinders the development and multiplication of bacteria.

It shows antibacterial activity against strains such as:

  • Streptococcus spp., Including S. pneumoniae (also moderately susceptible strains if the infection is related to the respiratory system);
  • Enterococcus spp. (Strains of E. faecium are often resistant), S. aureus and S. epidermidis – only penicillinase negative strains (approx. 90% of strains produce penicillinase);
  • Listeria monocytogenes;
  • coli (the percentage of resistant strains is about 40-60%);
  • Shigella (resistant strains are present, ampicillin shows better activity);
  • pylori (single resistant strains).


The indications for the administration of amoxicillin are:

  • upper respiratory tract infections,
  • lower respiratory tract infections,
  • inflammation of the genitourinary tract,
  • skin and soft tissue infections,
  • gastrointestinal infections.

In addition, amoxicillin can be administered for the treatment of oral cavity infections and as part of dental prophylaxis – after oral surgery.

Drug Mechanism

Amoxicillin is an antibiotic, semi-synthetic penicillin, with a structure similar to ampicillin. Penicillins are classified as β-lactam antibiotics. These antibiotics work by blocking one of the last steps in the biosynthesis of the bacterial cell wall, the so-called transpeptidation, i.e. the process of cross-linking the primary linear structure, thanks to which the bacterial cell wall obtains a permanent structure. This is due to the similar structure of the antibiotic and the natural substances used by bacteria to build the cell wall. Inhibition of the transpeptidase enzyme, which is involved in this process, results in the inhibition of the building of the cell wall and the subsequent breakdown of the bacterial cell. Due to this mechanism of action, β-lactam antibiotics show the strongest activity in the phase of the highest development of bacteria and their most intensive growth. Amoxicillin has a broad spectrum of antibacterial activity (it is active against many different species of bacteria). It is a bactericidal antibiotic, i.e. it kills the bacterial cell.

For an antibiotic to be effective in treating an infection, it is essential that it reaches a concentration at the site of the infection that is sufficient to inhibit the growth or kill the pathogenic microorganism, while still remaining safe for human cells. When both of these conditions are met, the microorganism is considered to be antibiotic sensitive. However, if the antibiotic fails to meet either of these conditions, it is deemed to be ineffective and the microorganism is considered to be antibiotic resistant. Antibiotic resistance can be innate or acquired as a result of genetic mutation in bacteria and selection of resistant strains, or through the transfer of resistance genes between bacterial cells (this is called horizontal transfer). One of the important mechanisms of bacterial resistance to β-lactam antibiotics is the degradation and hence inactivation of the antibiotic through enzymes called β-lactamases. This phenomenon can be prevented by administering substances that inhibit these enzymes together with the antibiotic. These substances are called β-lactamase inhibitors. They include, among others clavulanic acid and sulbactam. These substances permanently attach to the structures of the enzyme that breaks down the antibiotic and inactivate it, thereby allowing the antibiotic to work. Amoxicillin is a penicillin sensitive to beta-lactamases, therefore preparations containing amoxicillin and clavulanic acid are also used in the treatment of infections.

The bactericidal activity of β-lactam antibiotics depends on the length of time for which the concentration of the drug at the site of infection remains sufficiently high.

Taking instructions

After oral administration, amoxicillin is very well and quickly absorbed from the gastrointestinal tract, regardless of the meal and the type of diet. It is resistant to gastric juice. The biological half-life is approximately 1 hour; in renal failure, it is extended to 12–16 hours. Most of the dose is excreted renally within 6 hours, mostly unchanged.


The effect of Amoxicillin lasts for 6-8 hours after administration and 80-95% is absorbed from the gastrointestinal tract, regardless of the meal and the type of diet. It is resistant to gastric juice.

It penetrates well into the urine, bile, synovial, pleural, pericardial, peritoneal fluid, bronchial secretions, amniotic fluid and the middle ear. Approximately 60% of the dose is excreted through the kidneys within 6-8 hours, most of it unchanged.

Contraindications to use

To ensure your safety and well-being, it is important to carefully read the leaflet that accompanies your medication before use. This leaflet contains important information such as indications, contraindications, dosage, and potential side effects. If you have any questions or concerns, it is recommended that you consult with your doctor or pharmacist before using the medication. Improper use of any medication can be a serious threat to your health or even your life.

Amoxicillin is an antibiotic that should not be used in hypersensitivity to the active substance or any component of the preparation. In addition, it is not recommended to administer the drug to patients with suspected infectious mononucleosis.

Careful inquiry should be made concerning previous allergic reactions to penicillin antibiotics. Caution should be exercised in patients with impaired renal function, in people with reduced urine volume, crystalluria may occur. The drug can be used during pregnancy if the benefits of treatment outweigh the risks.

Drug interactions

Amoxicillin may interact with other medications.

It is not recommended to use the preparation in parallel with:

  • probenecid,
  • anticoagulants,
  • allopurinol,
  • warfarin,
  • methotrexate.

In addition, amoxicillin has an antagonistic effect, e.g. with: tetracyclines, macrolides, sulfonamides. However, it works synergistically with aminoglycosides.

Side effects

Taking medications that contain amoxicillin may cause some side effects. Common side effects include skin rash, nausea, diarrhea. Hives, itching and vomiting are uncommon. Mucosal and skin candidiasis, transient thrombocytopenia and haemolytic anemia very rarely develop. Severe allergic reactions are possible.

Some patients may experience allergic reactions after the use of beta-lactam antibiotics. They may appear in the form of skin reactions (such as rash, itching, hives), less often in the form of severe changes (e.g. swelling, blistering or exfoliative dermatitis). Allergic reactions can sometimes spread throughout the body and even lead to life-threatening anaphylactic shock. Serious allergic reactions occur more frequently after intravenous administration than after oral administration. If you experience an allergic reaction after taking an antibiotic, seek medical advice quickly as you may need to stop and switch to another antibiotic and have additional treatment for your allergy. An allergy to one of the penicillins is associated with an increased risk of an allergic reaction to another β-lactam drug. Importantly, hypersensitivity reactions may appear during the first administration of the antibiotic and in the case of subsequent administrations.

Other side effects that may occur after the use of β-lactam antibiotics are gastrointestinal complaints, such as nausea, loss of appetite, vomiting, flatulence, loose stools, diarrhea, and taste disturbances. They are usually mild and often disappear during or after treatment. Generally, these side effects can be reduced by taking amoxicillin with meals. It may also be beneficial to take preparations that restore the normal composition of the intestinal flora.

Important note:

This patient information is published for educational purposes only. The instructions and product properties quoted on this page follow the guidelines outlines by the drug manufacturer, but do not replicate it in all fullness. We strongly advise against using this information as a call to action of any kind, be it purchasing or using the drug without a proper medical consultation carried out first. Trademarks, names of companies and eventual studies are inserted for informational purposes and as a legal reference and respect for the copyright law and ethics.