Amoxicillin-Clavulanate

• Bacterial Sinusitis
• Ear Infections (Otitis Media)
• Skin and Soft Tissue Infections
• Lower Respiratory Tract Infections

Amoxicillin-clavulanate (commonly known by the brand name Augmentin) is a combination antibiotic used to treat a wide variety of bacterial infections. This medication pairs the broad-spectrum penicillin antibiotic amoxicillin with clavulanic acid, a beta-lactamase inhibitor that extends the drug's effectiveness against resistant bacteria.

Mechanism of Action

Amoxicillin works by interfering with bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs) and inhibits transpeptidation, the final step in peptidoglycan synthesis. This weakens the bacterial cell wall, leading to cell lysis and death. However, many bacteria produce beta-lactamase enzymes that can inactivate amoxicillin. Clavulanic acid addresses this by irreversibly binding to beta-lactamases, protecting amoxicillin from enzymatic degradation. This combination restores amoxicillin's effectiveness against beta-lactamase-producing strains of Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and many Enterobacteriaceae.

Available Formulations

Amoxicillin-clavulanate is available in multiple formulations to accommodate different patient populations. Tablets come in 250/125 mg, 500/125 mg, and 875/125 mg strengths (amoxicillin/clavulanate). Extended-release tablets (1000/62.5 mg) are available for once-daily dosing in certain infections. Chewable tablets and oral suspensions are available for pediatric patients or those who have difficulty swallowing tablets. The suspension is available in various strengths and requires refrigeration after reconstitution.

Medical Uses

Amoxicillin-clavulanate is indicated for treating infections caused by susceptible bacteria, including lower respiratory tract infections (pneumonia, bronchitis), acute bacterial sinusitis, acute otitis media, skin and soft tissue infections (including animal and human bites), urinary tract infections, and certain intra-abdominal infections when combined with other agents. It is particularly valuable when beta-lactamase-producing organisms are suspected or documented.

Dosing Guidelines

Dosing depends on the indication, infection severity, and patient factors. For most adult infections, 500 mg every 8 hours or 875 mg every 12 hours is standard. For severe infections, 875 mg every 12 hours or extended-release formulations may be used. Pediatric dosing is based on the amoxicillin component (typically 25-45 mg/kg/day divided every 8-12 hours). Taking the medication at the start of a meal can improve absorption and reduce gastrointestinal side effects. Duration varies by indication, typically 5-14 days.

Important Safety Information

Amoxicillin-clavulanate should not be used in patients with a history of penicillin allergy or previous cholestatic jaundice/hepatic dysfunction associated with amoxicillin-clavulanate. Cross-reactivity between penicillins and cephalosporins exists but is less common than historically believed. The medication can cause Clostridioides difficile-associated diarrhea. Hepatotoxicity occurs more frequently with amoxicillin-clavulanate than with amoxicillin alone and is more common in elderly patients, males, and with prolonged treatment.

Drug Interactions

Amoxicillin-clavulanate may reduce the efficacy of oral contraceptives. Probenecid decreases renal tubular secretion of amoxicillin, increasing plasma levels and prolonging half-life. Concurrent use with allopurinol increases the risk of skin rash. Warfarin anticoagulation may be enhanced; INR monitoring is recommended. Methotrexate excretion may be reduced, increasing toxicity risk.

Special Populations

Amoxicillin-clavulanate is pregnancy category B and can be used when clearly needed. It is excreted in breast milk in small amounts and is generally considered compatible with breastfeeding. Dose adjustment is required in patients with renal impairment (CrCl less than 30 mL/min). Elderly patients should be monitored for hepatotoxicity. The medication is widely used in pediatric patients for common infections like otitis media and sinusitis.