Overview
Benzathine benzylpenicillin is a long-acting penicillin antibiotic used primarily for the treatment and prevention of certain bacterial infections, particularly group A streptococcal infections and syphilis. It provides sustained antibacterial activity through slow absorption from intramuscular injection sites.
Mechanism of Action
Benzathine benzylpenicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death. The benzathine component provides prolonged release from intramuscular injection sites, maintaining therapeutic levels for extended periods.
Indications
- Treatment of group A streptococcal upper respiratory tract infections
- Secondary prevention of rheumatic fever
- Treatment of syphilis (all stages)
- Prophylaxis against recurrent rheumatic fever
- Treatment of yaws, bejel, and pinta
Dosage
Administered by deep intramuscular injection only. Adult dosage: For streptococcal infections: 1.2 million units single dose. For syphilis: 2.4 million units single dose (early syphilis) or weekly doses for 3 weeks (late syphilis). Pediatric dosage: Based on weight and indication. Never administer intravenously.
Contraindications
- Hypersensitivity to penicillins or other beta-lactam antibiotics
- History of severe allergic reactions to penicillin
- Intravenous administration
- Use in patients with history of penicillin-associated hemolytic anemia
Side Effects
- Injection site reactions (pain, tenderness, induration)
- Hypersensitivity reactions (rash, urticaria, anaphylaxis)
- Gastrointestinal disturbances
- Headache, dizziness
- Fever
- Hemolytic anemia
- Thrombocytopenia
- Neurotoxicity with high doses
Interactions
- Probenecid decreases renal tubular secretion of penicillin
- Tetracyclines may antagonize bactericidal effects
- Oral contraceptives: reduced efficacy reported
- Methotrexate: increased toxicity risk
- Warfarin: potential increased anticoagulant effect