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Antibiotic — Community-Acquired Pneumonia 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

Amoxicillin is a broad-spectrum aminopenicillin widely used for respiratory tract infections such as community-acquired pneumonia and infective COPD exacerbations. This entry covers its respiratory indications.

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: Acute exacerbations of chronic bronchitis (severe): 750 mg to 1 g every 8 hours for 10 days; Community acquired pneumonia: 500 mg to 1 g every 8 hours
Route: Oral
Frequency: Every 8 hours
Max: Indication-dependent
Adults and children >= 40 kg. Respiratory indications: acute exacerbations of chronic bronchitis (for severe infections) 750 mg to 1 g every 8 hours for 10 days; community acquired pneumonia 500 mg to 1 g every 8 hours. Related upper respiratory indications from the same SPC: acute bacterial sinusitis 250 mg to 500 mg every 8 hours or 750 mg to 1 g every 12 hours; acute otitis media 500 mg every 8 hours or 750 mg to 1 g every 12 hours; acute streptococcal tonsillitis and pharyngitis (for severe infections) 750 mg to 1 g every 8 hours for 10 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. Community acquired pneumonia, acute bacterial sinusitis and acute otitis media: 20 to 90 mg/kg/day in divided doses. Acute streptococcal tonsillitis and pharyngitis: 40 to 90 mg/kg/day in 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

Children weighing < 40 kg. Community acquired pneumonia, acute bacterial sinusitis and acute otitis media: 20 to 90 mg/kg/day in divided doses. Acute streptococcal tonsillitis and pharyngitis: 40 to 90 mg/kg/day in 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.

Verify in a children's formulary

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

It inhibits bacterial cell-wall synthesis by binding penicillin-binding proteins, causing lysis of susceptible bacteria. Its spectrum includes common respiratory pathogens such as Streptococcus pneumoniae.

Prescribing in practice

  • It is contraindicated in patients with penicillin allergy and can cause anaphylaxis, so a clear allergy history must be taken before prescribing — the primary safety point.
  • It is ineffective against beta-lactamase-producing organisms and atypical pathogens, so choice should follow local antimicrobial guidance and severity assessment such as CRB-65.
  • Dose frequency should be reduced in significant renal impairment per current prescribing references, and a maculopapular rash is characteristic if given in glandular fever.

Monitoring

Review clinical response within the expected timeframe and watch for hypersensitivity, diarrhoea or signs of antibiotic-associated colitis.

Counselling the patient

  • Complete the full prescribed course even once you feel better.
  • Stop and seek urgent help if you develop a rash, swelling or breathing difficulty.
  • Report severe or persistent diarrhoea.

Evidence & guidelines

NICE and BTS guidance recommend amoxicillin as a first-line option for many community-acquired respiratory infections, reflecting its activity against typical pathogens.

Reference: NICE NG138 (CAP 2019); BTS CAP Guidelines 2009 (updated); PHE antimicrobial 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).

Related

Curated clinical cross-links plus same-class fallbacks.

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