Antibiotic — Community-Acquired Pneumonia Pregnancy: Amoxicillin may be used in pregnancy when the potential benefits outweigh the potential risks. Animal studies do not indicate reproductive toxicity and limited human data do not indicate an increased risk of congenital malformations. Breastfeeding: excreted into breast milk in small quantities with a possible risk of sensitisation; use only after benefit/risk assessment by the physician in charge.

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: Community acquired pneumonia: 500 mg to 1 g every 8 hours (adults and children weighing 40 kg or more)

Route: Oral (powder for oral suspension; absorption is unimpaired by food). Therapy can be started parenterally per the IV formulation's dosing and continued with an oral preparation.

Frequency: Every 8 hours

SPC dosing applies to adults and children weighing 40 kg or more; children weighing 40 kg or more should be prescribed the adult dosage. OTHER RESPIRATORY / ENT INDICATIONS in the same SPC table: acute otitis media, acute streptococcal tonsillitis and pharyngitis, and acute exacerbations of chronic bronchitis - 500 mg every 8 hours, or 750 mg to 1 g every 12 hours; for severe infections 750 mg to 1 g every 8 hours for 10 days. Acute bacterial sinusitis - 250 mg to 500 mg every 8 hours or 750 mg to 1 g every 12 hours; for severe infections 750 mg to 1 g every 8 hours. NOTE FOR VERIFIER: the SPC posology table was flattened to plain text during fetch, so the exact indication-to-dose row groupings above should be confirmed against the SPC before publication. The dose selected should take into account the expected pathogens and their likely susceptibility, the severity and site of infection, and the age, weight and renal function of the patient. Duration should be determined by the type of infection and the response of the patient and should generally be as short as possible. Consideration should be given to the official treatment guidelines for each indication. NON-RESPIRATORY indications are listed separately in the SPC and are out of scope for this page. Elderly: no dose adjustment is considered necessary. Hepatic impairment: dose with caution and monitor hepatic function at regular intervals.

Paediatric dose

Route: Oral suspension (amoxicillin paediatric suspension is recommended for children under six months of age)

Frequency: In divided doses - twice daily dosing regimens should only be considered when the dose is in the upper range

Max: Not stated as an absolute daily maximum for these indications in the source; children weighing 40 kg or more should be prescribed the adult dosage

Children weighing under 40 kg. Acute bacterial sinusitis, acute otitis media, community acquired pneumonia, acute cystitis, acute pyelonephritis and 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. No single per-kg figure is stated, so dosePerKg is left null deliberately. Renal impairment in children under 40 kg: GFR greater than 30 mL/min - no adjustment; GFR 10 to 30 mL/min - 15 mg/kg twice daily; GFR less than 10 mL/min - 15 mg/kg as a single daily dose (parenteral therapy is preferred in the majority of these cases). Consideration should be given to the official treatment guidelines for each indication. Clinician to verify all paediatric doses against a children's formulary before publication.

Dose adjustments

Renal

Adults and children 40 kg or more - GFR greater than 30 mL/min: no adjustment necessary; GFR 10 to 30 mL/min: maximum 500 mg twice daily; GFR less than 10 mL/min: maximum 500 mg/day. Haemodialysis (adults and children over 40 kg): 500 mg every 24 hours, plus one additional 500 mg dose before dialysis and a further 500 mg dose after dialysis to restore circulating drug levels. Peritoneal dialysis: maximum 500 mg/day. Convulsions may occur in patients with impaired renal function or those receiving high doses.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance, to any of the penicillins, or to any of the excipients
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 and nausea (common)
Skin rash (common); urticaria and pruritus (uncommon)
Vomiting (uncommon)
Severe allergic reactions including angioneurotic oedema, anaphylaxis, serum sickness and hypersensitivity vasculitis (very rare); Kounis syndrome (not known)
Antibiotic associated colitis including pseudomembranous and haemorrhagic colitis (very rare); severe skin reactions such as erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, AGEP and DRESS (very rare)

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).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways