Amoxicillin

What It Is

Amoxicillin is one of the most commonly prescribed antibiotics, for both children and adults. It comes as capsules, tablets, chewable tablets, and a liquid suspension.

Like other antibiotics, it is used only for infections caused by bacteria. Health agencies stress that unnecessary antibiotic use contributes to antibiotic resistance, which makes infections harder to treat.

General mechanism

Amoxicillin binds to proteins that bacteria use to build their cell walls, blocking the final steps of cell wall construction. Without a stable cell wall, the bacteria weaken and burst. Some bacteria produce beta-lactamase enzymes that break down amoxicillin; adding clavulanate, which blocks these enzymes, helps amoxicillin work against some of those bacteria. Amoxicillin has no effect on viruses.

Common Terminology

Antibiotic

A medicine that kills bacteria or stops them from growing.

Penicillin

A family of antibiotics that includes amoxicillin.

Beta-lactam

A group of antibiotics, including penicillins and cephalosporins, that share a similar chemical structure.

Antibiotic resistance

When bacteria change so that antibiotics no longer work well against them.

Anaphylaxis

A severe, potentially life-threatening allergic reaction.

C. difficile

A bacterium that can cause severe diarrhea, sometimes after antibiotic use.

General Uses

Amoxicillin is prescribed for bacterial infections, such as:

• Middle ear infections (otitis media).
• Strep throat and some other throat infections.
• Some sinus infections.
• Certain lower respiratory infections, such as some types of pneumonia.
• Some urinary tract and skin infections.
• As part of combination treatment for H. pylori, a stomach bacterium linked to ulcers.

Common Side Effects

Commonly reported side effects include:

• Diarrhea.
• Nausea or vomiting.
• Skin rash.
• Stomach upset.
• Vaginal yeast infections.

Common Warnings and Precautions

Medication labels and health agencies describe several general warnings.

• People with a known allergy to penicillin or other beta-lactam antibiotics can have serious reactions to amoxicillin.
• Signs of a severe allergic reaction include hives, swelling of the face or throat, wheezing, and trouble breathing; these are generally treated as a medical emergency, and in the US people are advised to call 911.
• Severe, watery, or bloody diarrhea, even weeks after treatment, can be a sign of C. difficile infection.
• People with mononucleosis (mono) commonly develop a rash when given amoxicillin.
• Rare but serious skin reactions with blistering or peeling have been reported.

How It Works and How It Is Generally Used

This section describes general mechanism and use only; it does not include dosing information.

• Amoxicillin stops bacteria from building their cell walls properly.
• Without a sound cell wall, the bacteria break apart and die.
• It works against many, but not all, types of bacteria, and some bacteria have become resistant.
• Clavulanate is sometimes added to block an enzyme some bacteria use to destroy amoxicillin.
• The product, amount, schedule, and length of treatment are set by the prescriber and shown on the label.

Questions Often Discussed With a Clinician or Pharmacist

People often raise topics like these about amoxicillin.

• Whether an infection is likely bacterial or viral, and whether an antibiotic is needed.
• Any history of allergy to penicillin or other antibiotics.
• Which side effects are expected and which need prompt attention.
• Interactions with other medicines.
• Why completing the prescribed course is generally emphasized.

Questions to Ask a Healthcare Professional

General questions people often find useful to bring to an appointment:

• Is this infection caused by bacteria, and why is an antibiotic recommended?
• I have had a reaction to an antibiotic before; is amoxicillin safe for me?
• Which side effects are common, and which are serious?
• What should happen if a rash or diarrhea develops?
• Does amoxicillin interact with any of my other medicines?
• How will we know if the infection is improving?

Sources

This guide was written in plain language from the following authoritative references.

1. Amoxicillin — MedlinePlus (U.S. National Library of Medicine)
2. Amoxicillin — NHS (UK National Health Service)
3. Antibiotics — MedlinePlus (U.S. National Library of Medicine)

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