What is the typical dosing regimen for Amoxicillin (Amoxycillin)?

Amoxicillin Dosing Recommendations

For most common bacterial infections in adults, amoxicillin should be dosed at 500 mg three times daily or 875 mg twice daily, with higher doses of 4 g/day (given as 2 g twice daily) reserved for resistant organisms or severe infections. 1

Standard Adult Dosing

• Mild to moderate infections: 250-500 mg three times daily or 500 mg twice daily 1
• Moderate to severe infections: 500 mg three times daily or 875 mg twice daily 1
• High-dose therapy for resistant pathogens: 4 g/day divided as 2 g twice daily (particularly for respiratory infections with suspected penicillin-resistant Streptococcus pneumoniae) 1

The American Academy of Otolaryngology defines high-dose amoxicillin as 4 g/day for adults, which can be achieved through FDA-approved formulations combined with clavulanate. 1

Pediatric Dosing

• Standard dose: 40-45 mg/kg/day divided into doses every 8-12 hours 1
• Mild to moderate skin infections (≥3 months and <40 kg): 25 mg/kg/day every 12 hours OR 20 mg/kg/day every 8 hours 1
• High-dose therapy: 90 mg/kg/day divided twice daily for resistant organisms (maximum 4 g/day) 1

For children ≥3 months and ≥40 kg, adult dosing of 500 mg every 12 hours or 250 mg every 8 hours applies. 1

Dosing Frequency Considerations

Once or twice daily dosing is as effective as three times daily dosing for acute otitis media, with comparable clinical cure rates (RR 1.03,95% CI 0.99-1.07), recurrence rates, and adverse events. 2 This finding supports simplified dosing regimens to improve compliance, though traditional three-times-daily dosing remains standard for most indications. 1

Indication-Specific Dosing

Acute Bacterial Rhinosinusitis

• Adults: 500 mg twice daily (standard) or 2 g twice daily (high-dose for resistant organisms) 1
• Children: 45 mg/kg/day (standard) or 90 mg/kg/day (high-dose) divided twice daily 1

Erysipeloid

• Adults: 500 mg three times daily for 7-10 days 1

Acne Vulgaris (Adjunctive)

• Adults: 250 mg twice daily up to 500 mg three times daily 1

Human Bite Wounds

When combined with clavulanate: 875/125 mg twice daily orally 1

Duration of Therapy

• Most infections: 7-10 days 1
• Community-acquired pneumonia in children: 5 days is as effective as 10 days for uncomplicated cases (RR 1.01,95% CI 0.98-1.05) 3
• Urinary tract infections: Single 3 g dose may be effective in select cases, though this is not standard practice 4

Important Clinical Considerations

Resistance Patterns

Serum levels of amoxicillin increase linearly with dose, and gastrointestinal absorption is not a limiting factor, making high-dose therapy feasible without significantly increased adverse effects. 1 High-dose amoxicillin (4 g/day) is specifically designed to overcome penicillin-resistant S. pneumoniae by achieving adequate time above the minimum inhibitory concentration (MIC). 1

Combination with Clavulanate

When β-lactamase-producing organisms (Haemophilus influenzae, Moraxella catarrhalis) are suspected, clavulanate should be added. 1 The FDA-approved high-dose formulation provides 4 g amoxicillin with 250 mg clavulanate daily for adults, and 90 mg/kg amoxicillin with 6.4 mg/kg clavulanate (14:1 ratio) for children. 1

Renal Dosing

Dose adjustment is required in renal impairment, though specific adjustments were not detailed in the guidelines reviewed. 1

Common Pitfalls

• Avoid monotherapy when β-lactamase-producing organisms are likely 1
• Do not use for viral infections such as the common cold 5
• Diarrhea is common (40-43% of patients) and usually resolves after discontinuation, but pseudomembranous colitis can occur up to 2 months after treatment 1, 5, 6
• Standard-dose amoxicillin/clavulanate may be insufficient for severe Enterobacteriaceae infections; consider increasing to 6 times daily dosing 7

Pregnancy and Lactation

Amoxicillin is Pregnancy Category B and is distributed into breast milk but considered compatible with breastfeeding with minimal risk to the infant. 1