Products
Amoxicillin is commercially available in the form of tablets, film-coated tablets, dispersible tablets, as powder or granules for the preparation of a suspension, as an infusion and injection preparation, and as a veterinary drug. In addition to the original Clamoxyl, numerous generics are available today. Amoxicillin was launched in 1972 and has been approved in many countries since 1977. It is often given as a fixed combination with clavulanic acid (Augmentin, generics). This combination was released in many countries in 1983.
Structure and properties
Amoxicillin (C16H19N3O5S, Mr = 365.40 g/mol) is present in drugs as amoxicillin trihydrate or as the sodium salt amoxicillin sodium. The oral dosage forms contain amoxicillin trihydrate (amoxicillin – 3H2O), a white crystalline powder that is sparingly soluble in water and dissolves in dilute acids. Parenteral dosage forms contain amoxicillin sodium, a white, very hygroscopic powder that is very soluble in water. Amoxicillin is a semisynthetic aminopenicillin and structurally belongs to the beta-lactam antibiotics. It is stable to gastric acid, is well absorbed, and therefore can be administered orally, as a tablet or suspension.
Effects
Amoxicillin (ATC J01CA04) has bactericidal properties against Gram-positive and some Gram-negative pathogens. The effects are due to inhibition of bacterial cell wall synthesis by inhibition of transpeptidases involved in the synthesis of peptidoglycan. Amoxicillin has a short half-life of approximately 1 to 1.5 hours and is excreted primarily renally. Because it is sensitive to beta-lactamases, it is often combined with clavulanic acid, which binds and inhibits these bacterial enzymes as a “suicide inhibitor” and thus protects the penicillin from inactivation. Clavulanic acid itself has only weak antibacterial effects. It was isolated from the bacterium in 1972.
Indications
Amoxicillin is approved for the treatment of bacterial infectious diseases whose pathogens are sensitive to the antibiotic. It is used for respiratory tract infections, urinary tract infections, skin infections, digestive tract infections, and gynecologic infections, among others. Typical indications in practice include, for example, otitis media, streptococcal angina, acute bronchitis, acute bacterial rhinosinusitis, eradication of Helicobacter pylori, Lyme disease, endocarditis prophylaxis, and cystitis during pregnancy.
Dosage
According to the drug label. Amoxicillin is usually administered 3 times daily, sometimes 2 times daily. The tablets and suspension should be taken at the beginning of a meal because this promotes gastrointestinal tolerance and absorption. Suspensions for children are prepared fresh see Antibiotic Suspensions for Children.
Contraindications
- Hypersensitivity to penicillins and cephalosporins.
- Patients who developed jaundice or liver disorders during previous therapy
Full details of precautions and interactions can be found in the drug label.
Interactions
Amoxicillin is an organic anion and its elimination at the kidney is therefore inhibited by probenecid. It may decrease the efficacy of oral hormonal contraceptives by affecting the intestinal flora. Other interactions are possible with digoxin, allopurinol, and with vitamin K antagonists.
Adverse effects
The most common adverse effects associated with oral administration include diarrhea due to impairment of intestinal flora. This may be counteracted by delayed administration of probiotics. The skin and mucous membranes can become infected by Candida fungi, manifesting as vaginal thrush, oral thrush, and fungal skin infections, for example. Nausea and vomiting are common, especially at high doses, and can be reduced by taking at the beginning of a meal. Other digestive disturbances such as abdominal pain, loss of appetite, gastric pressure, and flatulence occur. Occasionally, a skin rash occurs, which manifests as spots, papules, redness, and as urticaria, and may be accompanied by an annoying itching sensation. Very rarely, a severe skin reaction such as toxic epidermal necrolysis develops.Severe hypersensitivity reactions such as anaphylactic shock are rare. Numerous other less common side effects are observed. Skin rashes under amoxicillin are common and in rare cases dangerous. For this reason, the patient should contact the doctor as a precaution if a skin rash occurs. In the event of a hypersensitivity reaction, treatment must be discontinued. Not all skin rashes are allergy mediated. For detailed information, see the article Rash on Amoxicillin.
