What is the recommended dosage frequency of Co-Amoxiclav (amoxicillin/clavulanic acid) for an adult patient with a typical bacterial infection and no significant comorbidities or allergies?

Co-Amoxiclav Dosing Frequency for Adults

For most adult patients with typical bacterial infections, Co-Amoxiclav should be taken either 500/125 mg every 8 hours (three times daily) or 875/125 mg every 12 hours (twice daily), with the twice-daily regimen preferred for respiratory infections and better tolerability. 1

Standard Dosing Regimens

Twice-Daily Dosing (Preferred for Most Infections)

• 875/125 mg every 12 hours is the standard dose for respiratory tract infections including acute bacterial rhinosinusitis, community-acquired pneumonia, and acute exacerbations of chronic bronchitis 2, 1
• This regimen provides clinical success rates of 91.5-93% for respiratory infections 2
• Twice-daily dosing causes significantly less severe diarrhea (1% vs 2%, p<0.05) compared to three-times-daily dosing 2
• The 875/125 mg formulation is also appropriate for skin and soft tissue infections 2

Three-Times-Daily Dosing

• 500/125 mg every 8 hours is indicated for mild-to-moderate infections when three-times-daily dosing is clinically preferred 1
• This regimen is specifically recommended for acute bacterial rhinosinusitis (10 days), chronic rhinosinusitis (10 days), and Group A streptococcal carrier eradication 2
• For animal or human bites, 500/125 mg twice daily is recommended 2

Clinical Decision Algorithm

Choose 875/125 mg twice daily when:

• Treating respiratory tract infections (sinusitis, pneumonia, bronchitis) 2, 1
• Patient compliance may be an issue (simpler regimen) 2
• Minimizing gastrointestinal side effects is a priority 2

Choose 500/125 mg three times daily when:

• Treating mild-to-moderate infections requiring 10-day therapy 2
• Treating acute bacterial rhinosinusitis with standard dosing 3, 2
• The 875 mg formulation is contraindicated or unavailable 1

Critical Dosing Considerations

Formulation Substitution Warning

Never substitute two 250/125 mg tablets for one 500/125 mg tablet - this results in excessive clavulanate dosing (250 mg vs 125 mg) and increases adverse effects 2, 1

Treatment Duration

• Respiratory infections typically require 7-10 days of therapy to prevent treatment failure and resistance development 2
• Acute bacterial rhinosinusitis: 5-7 days for uncomplicated cases 2
• Streptococcal infections: minimum 10 days to prevent acute rheumatic fever 2
• Five-day courses are only appropriate with high-dose regimens (2000/125 mg twice daily), not standard doses 2, 4

Administration Timing

Take Co-Amoxiclav at the start of meals to enhance clavulanate absorption and minimize gastrointestinal intolerance 1

Renal Impairment Adjustments

• GFR 10-30 mL/min: 500/125 mg or 250/125 mg every 12 hours 1
• GFR <10 mL/min: 500/125 mg or 250/125 mg every 24 hours 1
• Hemodialysis: 500/125 mg or 250/125 mg every 24 hours, with additional dose during and after dialysis 1
• Do not use 875/125 mg formulation if GFR <30 mL/min 1

Common Pitfalls to Avoid

• Incomplete treatment courses lead to resistance development and treatment failure 2
• Using standard doses for only 5 days (inadequate for most infections) 2
• Prescribing three-times-daily when twice-daily would suffice (increases side effects and reduces compliance) 2
• Failing to adjust for renal impairment (increases toxicity risk) 1