Beta-lactam + beta-lactamase inhibitor Pregnancy: eMC §4.6: animal studies do not indicate direct or indirect harmful effects with respect to pregnancy, embryonal/foetal development, parturition or postnatal development, and limited human data do not indicate an increased risk of congenital malformations. However, in a single study in women with preterm premature rupture of the foetal membrane, prophylactic amoxicillin/clavulanic acid was reported to be associated with an increased risk of necrotising enterocolitis in neonates. Use should be avoided during pregnancy unless considered essential by the physician. Breast-feeding: both substances are excreted into breast milk (nothing is known of the effects of clavulanic acid on the breastfed infant); diarrhoea and fungal infection of the mucous membranes are possible in the infant, so breast-feeding might have to be discontinued, and the possibility of sensitisation should be taken into account - use during breast-feeding only after benefit/risk assessment by the physician in charge.

Co-amoxiclav (Amoxicillin/Clavulanate)

Brand names: Augmentin

Used in: Sepsis Pneumonia Urinary Tract Infection Cellulitis & Skin Infection

Co-amoxiclav combines the broad-spectrum penicillin amoxicillin with the beta-lactamase inhibitor clavulanic acid, used for infections caused by beta-lactamase-producing bacteria resistant to amoxicillin alone.

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: 1000 mg/200 mg (amoxicillin/clavulanic acid) every 8 hours - adults and children weighing 40 kg or more

Route: Intravenous only - either slow intravenous injection over 3 to 4 minutes directly into a vein or via a drip tube, or infusion over 30 to 40 minutes. Not suitable for intramuscular administration.

Frequency: Every 8 hours

Max: This presentation provides a total daily dose of 3000 mg amoxicillin and 600 mg clavulanic acid when administered as recommended. If a higher daily amoxicillin dose is considered necessary, an alternative intravenous formulation of co-amoxiclav should be selected to avoid unnecessarily high daily doses of clavulanic acid. Treatment should not be extended beyond 14 days without review (eMC §4.2/§4.4).

eMC §4.2 (Co-Amoxiclav 1000 mg/200 mg Powder for Solution for Injection/Infusion). IMPORTANT: this is the INTRAVENOUS SPC - oral co-amoxiclav doses (e.g. 625 mg tablets, suspensions) are covered by different SPCs that were not fetched in this bundle and must be sourced separately before any oral regimen is published. Doses are expressed throughout in terms of amoxicillin/clavulanic acid content. Dose selection should take account of the expected pathogens and their likely susceptibility, the severity and site of infection, and the patient's age, weight and renal function; consideration should be given to local guidelines on appropriate dosing frequencies. SURGICAL PROPHYLAXIS: for procedures less than 1 hour, 1000 mg/200 mg to 2000 mg/200 mg given at induction of anaesthesia (2000 mg/200 mg requires an alternative intravenous formulation); for procedures greater than 1 hour, 1000 mg/200 mg to 2000 mg/200 mg at induction with up to 3 doses of 1000 mg/200 mg in 24 hours. Clear clinical signs of infection at operation require a normal course of intravenous or oral therapy post-operatively. DURATION: determined by the response of the patient; some infections (e.g. osteomyelitis) require longer periods. ELDERLY: no dose adjustment is considered necessary. HEPATIC IMPAIRMENT: dose with caution and monitor hepatic function at regular intervals. Treatment may be initiated with an intravenous preparation and completed with an appropriate oral presentation as considered appropriate for the individual patient. Children aged less than 3 months must be given amoxicillin/clavulanic acid by infusion only. Verify any under-18 use against a children's formulary. PROVENANCE NOTE: the openFDA record in this bundle is a US ORAL SUSPENSION 600 mg/42.9 mg per 5 mL label (paediatric only, 90 mg/kg/day divided every 12 hours) - it was not used for the adult intravenous dose above.

Paediatric dose

Dose: 25 mg/kg

Route: Intravenous (children aged less than 3 months by infusion only)

Frequency: Every 8 hours for children aged 3 months and over; every 12 hours for children aged less than 3 months or weighing less than 4 kg

Max: Applies to children weighing less than 40 kg. Children weighing 40 kg or more receive the adult dose of 1000 mg/200 mg every 8 hours.

eMC §4.2 states the paediatric dose as 25 mg/5 mg per kg - the 25 mg/kg figure entered here is the AMOXICILLIN component and is accompanied by clavulanic acid 5 mg/kg in this 1000 mg/200 mg presentation; do not apply the number without the ratio. RENAL IMPAIRMENT in children under 40 kg: CrCl 10 to 30 ml/min - 25 mg/5 mg per kg every 12 hours; CrCl below 10 ml/min - 25 mg/5 mg per kg every 24 hours; haemodialysis - 25 mg/5 mg per kg every 24 hours plus a dose of 12.5 mg/2.5 mg per kg at the end of dialysis, as serum concentrations of both amoxicillin and clavulanic acid are decreased. Verify against a children's formulary before use.

Dose adjustments

Renal

eMC §4.2 (adults and children 40 kg or more): dose adjustments are based on the maximum recommended level of amoxicillin. No dose adjustment is required if creatinine clearance is greater than 30 ml/min. CrCl 10 to 30 ml/min - initial dose of 1000 mg/200 mg then 500 mg/100 mg twice daily. CrCl below 10 ml/min - initial dose of 1000 mg/200 mg then 500 mg/100 mg every 24 hours. Haemodialysis - initial dose of 1000 mg/200 mg then 500 mg/100 mg every 24 hours, plus a dose of 500 mg/100 mg at the end of dialysis. Paediatric renal doses are given in the paedDose notes.

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

Contraindications

Hypersensitivity to the active substances, to any of the penicillins, or to any of the excipients (eMC §4.3)
History of a severe immediate hypersensitivity reaction (e.g. anaphylaxis) to another beta-lactam agent such as a cephalosporin, carbapenem or monobactam (eMC §4.3)
History of jaundice or hepatic impairment due to amoxicillin/clavulanic acid (eMC §4.3)

Side effects

Diarrhoea (common); nausea, vomiting and indigestion (uncommon) - diarrhoea, nausea and vomiting are the most commonly reported reactions overall
Mucocutaneous candidosis (common); overgrowth of non-susceptible organisms and antibiotic-associated colitis including pseudomembranous and haemorrhagic colitis (frequency not known)
Skin rash, pruritus and urticaria (uncommon); erythema multiforme (rare); Stevens-Johnson syndrome, toxic epidermal necrolysis, bullous exfoliative dermatitis, acute generalised exanthematous pustulosis (AGEP), DRESS and linear IgA disease (frequency not known)
Rises in AST and/or ALT (uncommon); hepatitis and cholestatic jaundice (frequency not known); dizziness and headache (uncommon); convulsions in patients with impaired renal function or on high doses, and aseptic meningitis (frequency not known)
Reversible leucopenia including neutropenia and thrombocytopenia (rare); reversible agranulocytosis and haemolytic anaemia (frequency not known); thrombophlebitis at the injection site (rare); angioneurotic oedema, anaphylaxis and Kounis syndrome (frequency not known); interstitial nephritis and crystalluria including acute renal injury (frequency not known)

Interactions

Allopurinol - concomitant use during treatment with amoxicillin can increase the likelihood of allergic skin reactions (eMC §4.4; the US label §7.3 states the incidence of rashes is substantially increased)
Oral anticoagulants (US labelling §7.2) - abnormal prolongation of prothrombin time / increased INR reported in patients receiving amoxicillin with oral anticoagulants; monitor and adjust the anticoagulant dose as necessary. eMC §4.8 also lists prolongation of bleeding time and prothrombin time as an undesirable effect.
Probenecid (US labelling §7.1) - decreases renal tubular secretion of amoxicillin, giving increased and prolonged blood levels; co-administration is not recommended
Oral contraceptives (US labelling §7.4) - efficacy may be reduced
The eMC §4.5 interaction section was not captured in this bundle - clinician to review it in the full SPC

Clinical monograph

How it works

Amoxicillin inhibits bacterial cell-wall synthesis by binding penicillin-binding proteins, while clavulanic acid irreversibly inactivates many bacterial beta-lactamases to protect amoxicillin from breakdown.

Prescribing in practice

Co-amoxiclav is contraindicated in anyone with a history of penicillin anaphylaxis and in those with previous co-amoxiclav-associated jaundice or hepatic dysfunction.
Cholestatic jaundice and hepatitis are recognised, may be delayed in onset and are more likely with longer courses and in older men.
Its broad spectrum carries a relatively high risk of antibiotic-associated diarrhoea including Clostridioides difficile, so it should be reserved for appropriate indications.

Monitoring

Monitor liver function if treatment is prolonged or if jaundice or abdominal symptoms develop.

Counselling the patient

Stop and seek advice if you develop a rash, jaundice or severe or bloody diarrhoea.
Take it with food to reduce stomach upset and complete the prescribed course.

Evidence & guidelines

The hepatic and C. difficile risks of co-amoxiclav are well established and reflected in MHRA advice and antimicrobial stewardship guidance.

Reference: NICE NG15 Surgical Site Infections; PHE 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