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Beta-lactam / Beta-lactamase inhibitor combination antibiotic Pregnancy: Compatible — widely used in pregnancy; avoid prophylactic use in PPROM (increased risk of neonatal necrotising enterocolitis per ORACLE trial).

Co-amoxiclav 625mg (COPD Exacerbation / CAP)

Brand names: Augmentin (500/125 mg tablets), Co-amoxiclav (generic)

Adult dose

Dose: 625 mg (amoxicillin 500 mg + clavulanate 125 mg) three times daily for 5 days
Route: Oral
Frequency: Three times daily (every 8 hours)
Max: 625 mg TDS (standard); 1 g TDS (severe CAP — specialist use)
COPD exacerbation (second-line or when penicillin-resistant organism suspected): 625 mg TDS × 5 days. CAP (non-severe, NICE NG120): amoxicillin 500 mg TDS preferred first-line; co-amoxiclav for more resistant organisms, aspiration pneumonia, or patients with comorbidities. Take with food to reduce GI side effects.

Paediatric dose

Route: Oral suspension or tablet
Frequency: Three times daily
Max: 40 mg/kg/day (amoxicillin component)
Concentration: 125/31 mg/5 mL or 250/62 mg/5 mL suspension mg/ml
Children: dosed on amoxicillin component — 25 mg/kg/day in 3 divided doses (standard) or 40 mg/kg/day (severe). Suspension: 125/31 for <6 years; 250/62 for >6 years.

Dose adjustments

Renal

eGFR 10–30 mL/min: use 375 mg (250/125) TDS. eGFR <10 mL/min: use 375 mg BD. Avoid high doses in significant renal impairment (clavulanate accumulates).

Hepatic

Use with caution in hepatic impairment — associated with cholestatic jaundice (clavulanate component). Avoid if history of co-amoxiclav-associated hepatic dysfunction.

Clinical pearls

  • GI tolerability: take with food — reduces diarrhoea and nausea significantly. Clavulanate is the main cause of GI side effects
  • Cholestatic jaundice: occurs in ~1/10,000 patients — more common in elderly males; onset up to 6 weeks after stopping. Do not rechallenge if this has occurred
  • Aspiration pneumonia: co-amoxiclav preferred over amoxicillin alone — covers anaerobes (Bacteroides) in addition to typical and atypical organisms
  • NICE NG120 (CAP): amoxicillin 500 mg TDS is first-line for non-severe CAP; co-amoxiclav reserved for moderate-severe or comorbid patients
  • Mononucleosis (EBV): amoxicillin/ampicillin causes a florid maculopapular rash in virtually all patients — check monospot if young patient with tonsillitis before prescribing

Contraindications

  • Penicillin allergy (immediate hypersensitivity / anaphylaxis)
  • History of co-amoxiclav-associated cholestatic jaundice
  • Mononucleosis (ampicillin/amoxicillin — high risk of maculopapular rash)

Side effects

  • GI upset: diarrhoea, nausea (most common — clavulanate component)
  • Antibiotic-associated diarrhoea / C. difficile colitis
  • Cholestatic jaundice (rare — clavulanate component; more common in elderly and men)
  • Rash (maculopapular — higher rate in glandular fever)
  • Hypersensitivity reactions (anaphylaxis — rare)

Interactions

  • Warfarin — INR may increase; monitor closely
  • Methotrexate — amoxicillin reduces MTX clearance; monitor toxicity
  • Oral contraceptives — theoretical reduced efficacy (no strong evidence)

Monitoring

  • Clinical response at 48–72 hours
  • LFTs if prolonged use or jaundice develops
  • C. difficile risk (diarrhoea persisting >48h)

Reference: BNFc; BNF; NICE NG120 Pneumonia; NICE NG115 COPD; NICE CKS Lower Respiratory Tract Infection. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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