Clinical detail

amoxicillin: clinical use

Name: amoxicillin: clinical use
Creator: iatroX

Amoxicillin is a prescription penicillin antibiotic used to treat infections caused by susceptible bacteria. It is usually taken by mouth as capsules or liquid; injectable formulations are generally used in hospital. It does not treat viral infections.

Amoxicillin 500 mg hard capsules — Current authorised Summary of Product Characteristics About amoxicillin

Reviewed byiatroX editorial team

Last reviewed12 Aug 2026

eMC product sources2 current documents reviewed

Also known asamoxicillin trihydrate, amoxicillin sodium

Professional view

Prescribing and clinical use

Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.

Clinical details

Prescribing considerations

Confirm that a bacterial pathogen is documented or sufficiently likely to be susceptible; amoxicillin alone is unreliable against beta-lactamase-producing organisms.
Take a detailed history of reactions to penicillins, cephalosporins and other beta-lactams before treatment; distinguish intolerance or a nonspecific rash from a confirmed immediate allergy.
Base dose selection on infection site and severity, expected pathogen, age, weight and renal function.
Avoid amoxicillin when infectious mononucleosis is suspected because a morbilliform rash is strongly associated with its use; such a rash is not by itself proof of lifelong penicillin allergy.

Consider antibiotic-associated colitis in diarrhoea arising during treatment or after it has finished.

With high doses or reduced urine output, maintain adequate hydration and urinary output and check catheter patency where relevant.

Be alert to drug-induced enterocolitis syndrome, reported mainly in children: protracted vomiting 1–4 hours after a dose can occur without skin or respiratory allergy signs and may progress to hypotension or shock.

Contraindications and cautions

Hypersensitivity to amoxicillin, another penicillin or a formulation excipient.
Previous severe immediate hypersensitivity, such as anaphylaxis, to another beta-lactam including a cephalosporin, carbapenem or monobactam.

Monitoring

Assess renal function where impairment is possible and adjust the product-specific regimen accordingly; accumulation can increase toxicity, including convulsions.
Use cautiously in hepatic impairment and monitor hepatic function periodically.
During prolonged treatment, periodically assess renal, hepatic and haematopoietic function.
Monitor INR or prothrombin time when an oral anticoagulant is used concurrently, particularly when amoxicillin is added or withdrawn.
Monitor clinical response and review culture and susceptibility results when available.
Remain alert to superinfection, severe cutaneous reactions, antibiotic-associated colitis and crystalluria.

Clinical pharmacology

Amoxicillin is a semisynthetic aminopenicillin that inhibits bacterial penicillin-binding proteins and peptidoglycan synthesis. Efficacy relates principally to the time that free concentrations remain above the organism’s minimum inhibitory concentration. Oral bioavailability is approximately 70%, peak concentration is usually reached at about one hour and food does not materially alter absorption.

Formulation and product differences

The cited 500 mg capsule must be swallowed intact and is unsuitable for someone unable to swallow capsules safely.
Oral liquids are available in different concentrations; doses must be measured using the concentration on the individual label.
The cited 125 mg/5 mL suspension contains sorbitol and, once reconstituted, is stored at 2–8°C and used within 14 days. These details are product-specific and may differ for another liquid.
Injectable amoxicillin has separate dosing and administration requirements and should not be extrapolated from oral instructions.

Amoxicillin 500 mg hard capsules — Current authorised Summary of Product Characteristics Amoxicillin Sugar Free 125 mg/ 5 ml Powder for Oral Suspension — Current authorised Summary of Product Characteristics Who can and cannot take amoxicillin

Dosage and duration

Dose and duration vary substantially with the infection, likely susceptibility, severity, route, age, weight and kidney function. Follow the individual prescription. These examples come from a current UK 500 mg capsule SmPC and are not universal prescribing instructions; children, people with renal impairment and users of other formulations may need different regimens.

Adults and children weighing at least 40 kg with selected susceptible oral infections such as acute bacterial sinusitis, pyelonephritis or a spreading dental abscess

Dose

250–500 mg every 8 hours, or 750 mg–1 g every 12 hours; severe infection may require 750 mg–1 g every 8 hours.

Duration

Determined by the infection and clinical response and generally kept as short as is effective.

Product-specific licensed example. Confirm the indication, severity, likely susceptibility and renal function before prescribing.

Amoxicillin 500 mg hard capsules — Current authorised Summary of Product Characteristics

Adults and children weighing at least 40 kg with community-acquired pneumonia treated using the cited oral capsule product

Dose

500 mg–1 g every 8 hours.

Duration

Individualised according to the infection and response.

This is a product-specific example, not a recommendation for every patient with pneumonia.

Amoxicillin 500 mg hard capsules — Current authorised Summary of Product Characteristics

Adults and children weighing at least 40 kg receiving Helicobacter pylori eradication treatment

Dose

750 mg–1 g twice daily, combined with a proton-pump inhibitor and another appropriate antibiotic.

Duration

7 days in the cited capsule SmPC.

A clinician must select the full combination; amoxicillin is not used alone for eradication.

Amoxicillin 500 mg hard capsules — Current authorised Summary of Product Characteristics

Amoxicillin 500 mg hard capsules — Current authorised Summary of Product Characteristics How and when to take amoxicillin

Interactions

This is not an exhaustive interaction list. Tell the prescriber or pharmacist about prescribed medicines, over-the-counter products, vitamins and supplements.

Probenecid

Reduces renal tubular secretion of amoxicillin and can produce higher, more prolonged concentrations; concurrent use is not recommended in the cited SmPC.

Amoxicillin 500 mg hard capsules — Current authorised Summary of Product Characteristics

Allopurinol

Concurrent treatment may increase the likelihood of an allergic skin reaction.

Amoxicillin 500 mg hard capsules — Current authorised Summary of Product Characteristics

Warfarin, acenocoumarol and other oral anticoagulants

Increased INR has been reported. Monitor coagulation when amoxicillin is started or stopped and adjust anticoagulant treatment if clinically required.

Amoxicillin 500 mg hard capsules — Current authorised Summary of Product Characteristics