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Drug Reference

amoxicillin/clavulanate

antibiotic· Brands: Augmentin, Clavulin, AmoxiclavIVPO

Mechanism of action
Amoxicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins. Clavulanate is a beta-lactamase inhibitor that covalently binds to beta-lactamases, preventing them from inactivating amoxicillin. This combination extends amoxicillin's spectrum to include beta-lactamase-producing bacteria.
Pharmacokinetics
Both components are well absorbed after oral administration, with amoxicillin achieving peak plasma concentrations in about 1 to 2 hours. They are widely distributed into tissues and fluids. Both are primarily excreted renally, with clavulanate also undergoing some hepatic metabolism. Plasma half-lives are approximately 1 hour for amoxicillin and 1.2 hours for clavulanate. Both are removed by haemodialysis.
Indications & dosing

Community-acquired pneumonia (adult)

Amoxicillin component; 500 mg with 125 mg clavulanate or 875 mg with 125 mg clavulanate.

  • adult · PO: 500–875 mg every 8-12 hours · Amoxicillin component; 500 mg with 125 mg clavulanate or 875 mg with 125 mg clavulanate.

Acute bacterial sinusitis (adult)

Amoxicillin component; 875 mg with 125 mg clavulanate.

  • adult · PO: 875 mg twice daily · Amoxicillin component; 875 mg with 125 mg clavulanate.

Acute otitis media (paediatric)

Amoxicillin component; for children under 40 kg. Typical suspension strengths: 125/31.25 mg per 5 mL or 250/62.5 mg per 5 mL.

  • pediatric · PO: 10–15 mg/kg/dose three times daily · Amoxicillin component; for children under 40 kg. Typical suspension strengths: 125/31.25 mg per 5 mL or 250/62.5 mg per 5 mL.

Skin and soft tissue infection (adult)

Amoxicillin component; 500 mg with 125 mg clavulanate or 875 mg with 125 mg clavulanate.

  • adult · PO: 500–875 mg every 8-12 hours · Amoxicillin component; 500 mg with 125 mg clavulanate or 875 mg with 125 mg clavulanate.

Animal or human bite (adult)

Amoxicillin component; 500 mg with 125 mg clavulanate or 875 mg with 125 mg clavulanate. Consider 5-7 day course.

  • adult · PO: 500–875 mg every 8-12 hours · Amoxicillin component; 500 mg with 125 mg clavulanate or 875 mg with 125 mg clavulanate. Consider 5-7 day course.

Dental abscess (adult)

Amoxicillin component; 500 mg with 125 mg clavulanate or 875 mg with 125 mg clavulanate. Usually 3-5 day course.

  • adult · PO: 500–875 mg every 8-12 hours · Amoxicillin component; 500 mg with 125 mg clavulanate or 875 mg with 125 mg clavulanate. Usually 3-5 day course.
Contraindications & precautions
  • Hypersensitivity to penicillins · Includes anaphylaxis, angioedema, urticaria; cross-reactivity with cephalosporins.
  • History of amoxicillin/clavulanate-associated cholestatic jaundice or hepatic dysfunction · May recur on rechallenge.
  • Check for allergy to penicillins or cephalosporins before initiating therapy.
  • Adjust dose in patients with renal impairment to prevent accumulation.
  • Use with caution in patients with hepatic impairment; monitor liver function.
  • Avoid in infectious mononucleosis because of the high risk of maculopapular rash.
  • Antibiotic-associated colitis can occur: discontinue if severe diarrhoea develops.
  • Prolonged use may lead to superinfection with non-susceptible organisms, including Candida.
Adverse effects
  • Diarrhoea
  • Nausea and vomiting
  • Skin rash
  • Oral or vaginal candidiasis
  • Anaphylaxis and angioedemaserious
  • Clostridium difficile-associated diarrhoeaserious
  • Cholestatic jaundiceserious
  • Severe cutaneous adverse reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis)serious
  • Blood dyscrasias (e.g., leukopenia, thrombocytopenia, agranulocytosis)serious
Renal & hepatic adjustment
  • eGFR 30+: No adjustment required for eGFR >30 mL/min.
  • eGFR 10–30: Reduce dose: e.g., 500/125 mg PO every 12 hours (or 250/125 mg every 8 hours). Alternatively, give normal dose every 12 hours instead of every 8 hours.
  • eGFR 0–10: Reduce dose significantly: e.g., 500/125 mg PO every 24 hours (or 250/125 mg every 12 hours). For patients on haemodialysis, give a supplemental dose after dialysis.
  • Hepatic impairment (mild): No dose adjustment required, but use with caution. Monitor for signs of hepatotoxicity.
  • Hepatic impairment (moderate): Use with caution. Consider extended interval dosing or reduced doses if needed. Monitor liver function tests.
  • Hepatic impairment (severe): Avoid use; consider alternative antibiotic if possible. If necessary, use with extreme caution and monitor closely. (avoid)
Monitoring, pregnancy & toxicity
  • Renal function · Before treatment and periodically during prolonged therapy
  • Hepatic function · Monitor for hepatotoxicity (jaundice, raised LFTs), especially in prolonged therapy or liver disease
  • Allergic reactions · Observe for rash, pruritus, and signs of anaphylaxis during therapy
  • Signs of superinfection · Monitor for new infections (e.g., candidiasis, Clostridioides difficile) during prolonged therapy
  • Prothrombin time/INR · If patient on anticoagulants, monitor INR regularly
  • Pregnancy: Amoxicillin/clavulanate is generally considered safe in pregnancy. It may be used when indicated, as amoxicillin is well established in pregnancy; clavulanate has limited but reassuring data. It should be prescribed with caution, particularly in the third trimester, and only when the benefits outweigh the risks.
  • Toxicity: Nausea, vomiting and diarrhoea are common; in overdose these may be severe and cause dehydration. · Supportive care, rehydration with oral fluids or IV fluids, and correction of electrolyte imbalances.
  • Toxicity: Neurotoxicity (e.g., seizures) can occur with high doses, especially in patients with renal impairment. · Stop the drug, manage seizures with benzodiazepines, and consider haemodialysis in severe cases.
  • Toxicity: Hypersensitivity reactions, ranging from rash to anaphylaxis. · Discontinue treatment; treat anaphylaxis with adrenaline (epinephrine) according to local protocols.
  • Toxicity: Crystalluria can occur with high doses of amoxicillin in concentrated urine. · Maintain adequate hydration, monitor urine output, and monitor renal function.
Clinical notes
Used for a range of infections including otitis media, sinusitis, lower respiratory tract infections, urinary tract infections, skin and soft tissue infections, and animal bites. Reserve for infections caused by beta-lactamase-producing organisms or when amoxicillin alone is ineffective. Common adverse effects include diarrhoea, nausea, and rash. Monitor for pseudomembranous colitis. Adjust dose in renal impairment. Avoid in penicillin allergy.

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BNF; local formulary