Antibiotic (Penicillin) Pregnancy: May be used in pregnancy when potential benefits outweigh the potential risks; animal studies show no reproductive toxicity and limited human data do not indicate increased risk of congenital malformations.

Amoxicillin

Brand names: Amoxil

Used in: Pneumonia COPD Urinary Tract Infection Meningitis & Encephalitis

Amoxicillin is a broad-spectrum aminopenicillin antibiotic for respiratory, ENT, urinary and other infections, and part of Helicobacter pylori regimens.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 250 mg to 500 mg every 8 hours, or 750 mg to 1 g every 12 hours

Route: Oral

Frequency: Every 8 hours (or every 12 hours)

Max: Indication-dependent (e.g. Lyme disease up to 4 to 6 g/day in divided doses)

Adults and children >= 40 kg. Dose varies by indication. Severe infections / acute pyelonephritis / dental abscess with spreading cellulitis: 750 mg to 1 g every 8 hours. Acute cystitis: 3 g twice daily for one day. Acute otitis media: 500 mg every 8 hours, or 750 mg to 1 g every 12 hours. Community acquired pneumonia: 500 mg to 1 g every 8 hours. Typhoid/paratyphoid: 500 mg to 2 g every 8 hours. Prophylaxis of endocarditis: 2 g orally single dose 30 to 60 min before procedure. H. pylori eradication: 750 mg to 1 g twice daily with a PPI and another antibiotic for 7 days. Lyme disease early stage: 500 mg to 1 g every 8 hours (max 4 g/day) for 14 days; late stage: 500 mg to 2 g every 8 hours (max 6 g/day) for 10 to 30 days. Duration should generally be as short as possible.

Paediatric dose

Dose: 40 mg/kg

Route: Oral

Frequency: Per day in divided doses (range 20 to 90 mg/kg/day depending on indication)

Max: Children >= 40 kg should receive the adult dosage

Children weighing < 40 kg. Most indications (acute bacterial sinusitis, acute otitis media, community acquired pneumonia, acute cystitis, acute pyelonephritis, dental abscess with spreading cellulitis): 20 to 90 mg/kg/day in divided doses. Acute streptococcal tonsillitis and pharyngitis: 40 to 90 mg/kg/day in divided doses. Typhoid and paratyphoid fever: 100 mg/kg/day in three divided doses. Twice-daily dosing regimens should only be considered when the dose is in the upper range. Paediatric Suspension is recommended for children under six months of age. Verify against a children's formulary.

Dose adjustments

Renal

In renal impairment the dose should be adjusted according to the degree of impairment (see SPC §4.2 renal impairment table; full table truncated in source).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

US labelling (FDA)

Reference — US labelling, may differ from UK

Adults and Pediatric Patients greater than 40 kg: 500 or 875 mg every 12 hours or 250 or 500 mg every 8 hours, based on the amoxicillin component. ( 2.2 , 2.3 ) Pediatric patients aged 12 weeks (3 months) and older: 25 to 45 mg/kg/day every 12 hours or 20 to 40 mg/kg/day every 8 hours, up to the adult dose. ( 2.3 ) Neonates and infants less than 12 weeks of age: 30 mg/kg/day divided every 12 hours, based on the amoxicillin component. Use of the 125 mg/5 mL oral suspension is recommended. ( 2.3 ) 2.1 Important Administration Instructions Amoxicillin and Clavulanate Potassium may be taken without regard to meals; however, absorption of clavulanate potassium is enhanced when Amoxicillin and …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2024-04-30. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Hypersensitivity to amoxicillin, to any of the penicillins, or to any excipient
History of a severe immediate hypersensitivity reaction (e.g. anaphylaxis) to another beta-lactam agent (e.g. a cephalosporin, carbapenem or monobactam)

Side effects

Diarrhoea
Nausea
Skin rash
Vomiting (uncommon)
Urticaria and pruritus (uncommon)

Interactions

Probenecid: decreases renal tubular secretion of amoxicillin; co-administration not recommended
Oral anticoagulants: may prolong prothrombin time (raised INR); monitor
Allopurinol: increases the risk of rash
Oral contraceptives: efficacy may be reduced

Clinical monograph

How it works

A beta-lactam that inhibits bacterial cell-wall synthesis by binding penicillin-binding proteins.

Prescribing in practice

Avoid in penicillin allergy.
It commonly causes a non-allergic rash if given during glandular fever (infectious mononucleosis).
Like other antibiotics it can predispose to Clostridioides difficile and, rarely, hypersensitivity.

Monitoring

Short courses need no routine monitoring; review the response.

Counselling the patient

Complete the course.
Report a rash, wheeze or facial swelling (possible allergy).
Report severe or prolonged diarrhoea.

Evidence & guidelines

A first-line antibiotic for many community infections (NICE/local antimicrobial guidance).

Reference: NICE NG138 (Pneumonia); PHE Antibiotic Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways