Amoxicillin/Clavulanate (Co-amoxiclav) Dosing and Administration
For adults with acute bacterial rhinosinusitis or respiratory tract infections, prescribe amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days as first-line therapy. 1, 2
Standard Adult Dosing
Oral Formulations
Standard dose:
- 875 mg/125 mg twice daily is the preferred regimen for most community-acquired respiratory infections 1, 3
- Alternative: 500 mg/125 mg three times daily 4
- Duration: 5-10 days for acute bacterial rhinosinusitis 1, 2
High-dose regimen (for resistant pathogens):
- 2000 mg/125 mg (extended-release) twice daily for drug-resistant Streptococcus pneumoniae or β-lactamase-producing organisms 5, 6
- Standard high-dose: 4 g amoxicillin with 250 mg clavulanate per day for adults 5
Intravenous Dosing
For hospitalized patients with severe infections:
- 1000 mg/200 mg four times daily is the standard IV dose 7
- Consider increasing to six times daily for severe Enterobacteriaceae infections with MIC of 8 mg/L, as only 65% of patients reach therapeutic targets with standard dosing 8
Administration Guidelines
Critical administration instructions:
- Take at the start of meals to minimize gastrointestinal intolerance and enhance clavulanate absorption 9
- Do not substitute different formulations - the 875/125 mg tablets are not interchangeable with suspension formulations due to different clavulanate ratios 9
- Store properly in cool conditions; heat exposure significantly degrades the medication, particularly in hot climates 10
Pediatric Dosing (3 months and older)
High-dose pediatric regimen:
- 90 mg/kg/day of amoxicillin with 6.4 mg/kg/day of clavulanate divided into two doses 5, 11
- Maximum: not to exceed 2 g every 12 hours 4
- Duration: 10-14 days for children (longer than adults) 11
Contraindications and Precautions
Absolute contraindications:
- History of serious hypersensitivity reactions (anaphylaxis, Stevens-Johnson syndrome) to penicillins or cephalosporins 12
- History of cholestatic jaundice or hepatic dysfunction associated with prior amoxicillin-clavulanate use 12
Relative contraindications and warnings:
- Penicillin allergy: Use alternative agents (respiratory fluoroquinolones or doxycycline for adults) 1, 13
- Hepatic impairment: Dose with caution and monitor hepatic function regularly 9
- Pregnancy Category B: Use only if clearly needed, though generally considered safe 9
- Nursing mothers: Excreted in breast milk; exercise caution 9
Clinical Context and Resistance Considerations
The addition of clavulanate is specifically indicated when β-lactamase-producing organisms are suspected:
- β-lactamase-producing Haemophilus influenzae (approximately 50% of strains) 4
- β-lactamase-producing Moraxella catarrhalis (90-100% of strains) 4
- Penicillin-resistant S. pneumoniae (25-50% of strains show resistance) 4
Important distinction: Plain amoxicillin remains highly active against S. pneumoniae and is the most active oral β-lactam against streptococci 5. The clavulanate component does not enhance activity against S. pneumoniae but preserves amoxicillin activity against β-lactamase producers 5.
Common Pitfalls to Avoid
Do not:
- Prescribe for viral upper respiratory infections - antibiotics provide minimal benefit (number needed to treat = 18) with significant harm (number needed to harm = 8) 1, 13
- Use amoxicillin alone for empiric therapy when β-lactamase producers are likely 11
- Substitute different amoxicillin-clavulanate formulations interchangeably 9
- Continue beyond 7 days without reassessment if no clinical improvement 1, 2
Adverse effects:
- Gastrointestinal effects are more common with clavulanate than amoxicillin alone 1, 12
- Diarrhea occurs less frequently with twice-daily 875/125 mg dosing compared to three-times-daily 500/125 mg dosing 14
- Clostridioides difficile infection risk is higher with amoxicillin-clavulanate than amoxicillin alone 12
Treatment Failure Management
If no improvement by 7 days or worsening at any time: