Overview
Amoxicillin is a broad-spectrum, bactericidal, beta-lactam antibiotic in the aminopenicillin class. It is commonly used to treat various bacterial infections by inhibiting bacterial cell wall synthesis. It has good oral bioavailability and is often combined with clavulanic acid to overcome beta-lactamase resistance.
Mechanism of Action
Amoxicillin binds to penicillin-binding proteins (PBPs) on the bacterial cell wall, inhibiting the final transpeptidation step of peptidoglycan synthesis. This leads to cell lysis and death due to osmotic instability. It is bactericidal against susceptible organisms.
Indications
- Acute otitis media
- Streptococcal pharyngitis/tonsillitis
- Acute bacterial sinusitis
- Community-acquired pneumonia
- Acute exacerbations of chronic bronchitis
- Skin and skin structure infections
- Urinary tract infections
- Helicobacter pylori eradication (in combination therapy)
- Lyme disease
- Prophylaxis of bacterial endocarditis
Dosage
Adults: 250-500 mg every 8 hours or 500-875 mg every 12 hours depending on infection severity. Children: 20-90 mg/kg/day divided every 8-12 hours. Duration typically 5-14 days depending on infection. Renal impairment requires dosage adjustment.
Contraindications
- History of serious hypersensitivity reactions (e.g., anaphylaxis) to amoxicillin or other beta-lactam antibiotics
- History of amoxicillin-associated cholestatic jaundice/hepatic dysfunction
Side Effects
- Diarrhea
- Nausea
- Vomiting
- Rash
- Urticaria
- Pruritus
- Headache
- Abdominal pain
- Vaginal candidiasis
- Elevated liver enzymes
- Black hairy tongue
- Tooth discoloration in children (reversible)
Interactions
- Probenecid decreases renal tubular secretion of amoxicillin
- Allopurinol may increase incidence of skin rash
- Oral contraceptives may have reduced efficacy
- Warfarin may have enhanced anticoagulant effect
- Methotrexate toxicity may be increased