Bacitracin injection - Drug Monograph

Introduction

Bacitracin injection is a polypeptide antibiotic derived from Bacillus subtilis that has been used clinically since the 1940s. While topical bacitracin formulations are widely available, the parenteral form represents a specialized antimicrobial agent reserved for specific serious infections. This injectable formulation contains bacitracin as the zinc salt to enhance stability. Due to its significant nephrotoxicity potential, systemic bacitracin use has dramatically declined with the advent of safer antibiotics but remains an option in specific clinical scenarios where alternatives are limited.

Mechanism of Action

Bacitracin exerts its bactericidal effect by interfering with bacterial cell wall synthesis. Specifically, it inhibits the dephosphorylation of the phospholipid carrier (undecaprenyl pyrophosphate) that transports peptidoglycan precursors across the cytoplasmic membrane. This disruption prevents the regeneration of the carrier molecule, effectively halting peptidoglycan synthesis and subsequent cell wall formation. Bacitracin is primarily effective against Gram-positive organisms, including many antibiotic-resistant strains, with minimal activity against Gram-negative bacteria due to their outer membrane barrier.

Indications

Bacitracin injection is indicated for the treatment of:

• Severe staphylococcal infections, including pneumonia and empyema, when caused by susceptible strains and when other antibiotics are ineffective or contraindicated
• Serious infections caused by susceptible streptococcal species
• As part of combination therapy for infantile pneumonia caused by susceptible staphylococci

Due to its toxicity profile, bacitracin injection should be reserved for situations where safer alternatives cannot be used and the benefits outweigh the risks.

Dosage and Administration

• Administer by deep intramuscular injection only
• Rotate injection sites to minimize tissue irritation
• Do not administer intravenously due to severe local irritation and thrombophlebitis
• Renal function must be monitored closely, and dosage adjustments made accordingly
• Duration of therapy typically should not exceed 12 days due to nephrotoxicity risk

Pharmacokinetics

Contraindications

• History of hypersensitivity to bacitracin or any component of the formulation
• Patients with significant renal impairment (creatinine clearance <30 mL/min)
• Concomitant use with other nephrotoxic agents unless absolutely necessary
• Intravenous administration (absolute contraindication)

Warnings and Precautions

• Use with extreme caution in patients with pre-existing renal impairment
• Monitor for signs of neurotoxicity (tingling, numbness, muscle weakness)
• Superinfection with resistant organisms may occur
• Cross-hypersensitivity with other polypeptide antibiotics may occur
• Use during pregnancy only if clearly needed (Category C)
• Exercise caution in elderly patients due to increased nephrotoxicity risk

Drug Interactions

• Aminoglycosides: Increased risk of nephrotoxicity (avoid combination)
• Polymyxins: Enhanced nephrotoxic potential (avoid combination)
• Vancomycin: Potential additive nephrotoxicity (use with extreme caution)
• Diuretics: May enhance nephrotoxicity (monitor closely)
• Other nephrotoxic agents (cisplatin, amphotericin B, NSAIDs): Increased renal damage risk

Adverse Effects

• Injection site pain, induration, and sterile abscess formation
• Mild elevation in serum creatinine
• Proteinuria

• Acute tubular necrosis and acute renal failure
• Neurotoxicity (paresthesias, numbness, muscle weakness)
• Anaphylactoid reactions
• Blood dyscrasias (neutropenia, thrombocytopenia)
• Severe skin reactions

Monitoring Parameters

• Serum creatinine daily (more frequently if renal function declines)
• Urinalysis for proteinuria and casts
• Fluid intake and output measurements
• BUN and electrolytes (especially potassium)
• Complete blood count with differential

• Neurological assessment for paresthesias or weakness
• Signs of superinfection
• Injection sites for local reactions

Patient Education

• Report immediately any changes in urinary output, swelling, or unusual tingling/numbness
• Maintain adequate hydration unless contraindicated
• Understand that this medication requires close medical supervision
• Be aware of potential kidney damage and the importance of monitoring
• Report any signs of allergic reaction (rash, itching, difficulty breathing)
• Complete the full course of therapy as prescribed
• Do not use any other medications without consulting your healthcare provider

References

1. Gilbert DN, Chambers HF, Eliopoulos GM, et al. The Sanford Guide to Antimicrobial Therapy. 52nd ed.; 2022. 2. Bacitracin injection prescribing information. FDA-approved labeling. 3. Brunton LL, Hilal-Dandan R, Knollmann BC. Goodman & Gilman's: The Pharmacological Basis of Therapeutics. 13th ed. McGraw-Hill; 2017. 4. Lexicomp Online. Bacitracin (Systemic) monograph. Wolters Kluwer Clinical Drug Information; 2023. 5. Mandell GL, Bennett JE, Dolin R. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Elsevier; 2019. 6. McEvoy GK, ed. AHFS Drug Information. American Society of Health-System Pharmacists; 2023. 7. ClinicalTrials.gov. Historical data on bacitracin safety and efficacy. U.S. National Library of Medicine.