Amoxicillin is a broad-spectrum antibiotic used to treat various bacterial infections, including respiratory tract infections (pneumonia, angina, bronchitis), ear, skin, and urinary tract infections. It has a high safety profile and can be taken by most adults and children. Like other antibiotics, it is not effective against viral infections such as seasonal colds and flu. Amoxicillin is one of the most commonly used antibiotics in the primary care setting. Every year, amoxicillin is prescribed about 30 million times in the US alone. The drug was developed in 1972 and has been sold by GlaxoSmithKline as Amoxil. However, the patent for the drug has already expired, and other manufacturers sell it under various names.

Mechanism of action

Amoxicillin is similar to penicillin in its action against sensitive bacteria at the stage of reproduction. The drug destroys their cell walls by disrupting protein synthesis. Without a protective membrane, the bacteria cannot exist and dissolve without a chance of regeneration. However, Amoxicillin is not effective against bacteria that produce a special enzyme called penicillinase. Therefore, amoxicillin is sometimes combined with other antibiotics that are insensitive to penicillinase, usually with сlavulanic acid.

Pharmaceutical form of Amoxicillin

Amoxicillin for oral administration is available in tablets, capsules, chewable tablets, and oral suspension. Children’s preparations may come in various flavors. Some forms are used for injection, but this is usually only done in the hospital. Veterinary amoxicillin should not be used for humans and vice versa.

Administration and dosages

The drug can be taken before or after a meal. Amoxicillin is not destroyed by stomach acid, so food intake does not affect its absorption. The maximum concentration of the drug is reached 1–2 hours after oral administration.

The standard dose for adults and children over 10 years old is 250–500 mg 3 times daily. In severe infections, it can be increased to 750 mg 3 times daily. For children under 10 years old (<40 kg), the dose should be halved.

• Acute gastrointestinal and gynecological infections for adults: 1.5–2 g 3 times daily.
• Otitis media (middle ear infection) and similar infections in children: a two-time dose of amoxicillin is sufficient.
• Chronic diseases and recurrent infections: 0.75–1 g 3 3 times daily.
• Leptospirosis: 0.5–0.75 g 4 times daily for 6–12 days.
• Listeriosis: 0.5 g 3 times daily for 6–12 days.
• Salmonella carriage: 1.5–2 g 3 times daily for 2–4 weeks.
• In patients with moderate and severe renal impairment dose reduction may be required.

For more detailed dosage instructions, see the original leaflet.

Contraindications of Amoxicillin

Hypersensitivity to β-lactam antibiotics (penicillins, cephamycins, carbapenems, etc.);

Should be taken with caution in patients with: impaired renal function; severe digestive disorders associated with vomiting and diarrhea; allergic diathesis; asthma; hay fever; viral infections; acute lymphoblastic leukemia; infectious mononucleosis.

Use during pregnancy and lactation

Amoxicillin crosses the placental barrier and is excreted in small amounts in breast milk. Considering the use of amoxicillin during pregnancy, the expected benefit of therapy and the potential risk to the fetus should be carefully weighed. Use amoxicillin with caution during breastfeeding.

Side effects of Amoxicillin

Side effects can be of several types depending on how often they occur: frequent (1%–10%), rare (0.01%–1%), and very rare (less than 0.01%).

Frequent side effects of amoxicillin include: drowsiness, headache, dizziness; nausea, diarrhea; tachycardia, rash, etc.

Rare: general weakness, decreased blood pressure, vomiting, indigestion; anxiety, ataxia, behavior change, peripheral neuropathy, sleep disturbance, depression, tremor, confusion; neutropenia, thrombocytopenia, agranulocytosis, interstitial nephritis, increased serum creatinine concentration.

Very rare: hyperesthesia, impaired vision, smell, and tactile sensitivity, hallucinations, acute liver failure, bloody diarrhea, pseudomembranous colitis, black tongue, photosensitivity, swelling of the skin, mucous membranes, anemia, etc.

Drug interactions

• Amoxicillin administration can increase the absorption time of digoxin (a drug used in the treatment of chronic heart failure).
• Simultaneous use of amoxicillin with other bacteriostatic drugs (macrolides, tetracyclines, sulfonamides, and chloramphenicols) is not recommended. This can decrease or eliminate the effects of the drugs. Simultaneous use of amoxicillin and aminoglycosides can increase the pharmaceutical effect.
• Simultaneous use of amoxicillin and disulfiram is not recommended.
• Simultaneous use of amoxicillin and methotrexate can lead to increased toxicity of the latter.
• Ascorbic acid increases the absorption of amoxicillin. Antacids, glucosamine, laxative drugs, and aminoglycosides slow down and reduce absorption.
• Amoxicillin increases the effectiveness of indirect anticoagulants and reduces the effectiveness of estrogen-containing oral contraceptives.
• Diuretics, allopurinol, oxyphenbutazone, phenylbutazone, non-steroidal anti-inflammatory drugs, and other drugs that block tubular secretion increase the concentration of amoxicillin in the blood.
• Allopurinol increases the risk of skin rashes.

The list of contraindications and drug interactions in this article is not complete, for full information please refer to the original leaflet.

Additional remarks

Developed back in 1972, amoxicillin remains the first-choice drug for the treatment of widespread bacterial infections. Those include upper and lower respiratory infections, as well as gastrointestinal infections caused by h.rulori, a common gastric pathogen. Frequent adverse reactions from the gastrointestinal tract are one of the significant drawbacks of amoxicillin. Taking amoxicillin in the form of dissolvable tablets helps to reduce side effects, provides an increase in bioavailability, and improves treatment outcomes.

Amoxicillin is affordable, safe, and well-tolerated by adults and children, although only a medical professional can decide whether its use is reasonable in any given case. The right choice of antibiotics and their dosages are very important for a satisfactory treatment outcome. Review the full list of contraindications and be sure to mention any medical conditions and medications you are taking to your doctor.