Soft tissue infection prophylaxis with gentamicin encapsulated in multivesicular liposomes: Results from a prospective, randomized trial

Objectives: Systemically administered antibiotic agents are not evenly distributed in the body, which frequently results in subtherapeutic regional drug concentrations, particularly in areas of poor vascularization, including wound sites. We have developed a lipid-based drug delivery system to provide prolonged levels of gentamicin in local tissues after local administration. Multivesicular liposomes are microspheres composed of lipid bilayer membranes surrounding multiple aqueous compartments that can contain drug. The preparation may be effective for the prevention and treatment of a variety of infections, including infections associated with indwelling vascular catheters. Design: Prospective, randomized trial. Setting: Animal laboratory. Subjects: Mice, 6 to 12 wks of age, weighing 20 to 30 g. Interventions: We administered 0.5 mg of gentamicin encapsulated in multivesicular liposomes to dorsal subcutaneous tissue in mice. Animals were inoculated with 10⁵ to 10⁷ colony-forming units (cfu) of Staphylococcus aureus 2, 4, 6, and 8 days later. The cfu/g of tissue values were determined 2 days after inoculation. Measurements and Main Results: With a 10⁷ cfu challenge, animals that received 2- and 4-day pretreatment with multivesicular liposome/gentamicin had a 4 log₁₀ reduction in cfu/g of tissue compared with controls. When 10⁵ cfu of Staphylococcus aureus were inoculated after 2- and 4-day pretreatment with multivesicular liposome/gentamicin, a 6 log₁₀ reduction in bacteria colony-forming units was observed. Conclusion: Local injection of multivesicular liposome/gentamicin provides sustained drug concentrations in regional tissues that protect against a massive bacterial challenge for at least four subsequent days.