Tobramycin liposomes. Single subconjunctival therapy of pseudomonal keratitis

The authors compared 24 doses of hourly topical fortified tobramycin (Group A) therapy with a single subconjunctival administration of multivesicular megaliposome-encapsulated tobramycin (Group B) and free subconjunctival tobramycin (Group C) in treating a rabbit model of keratitis caused by Pseudomonas aeruginosa. One cornea each of 50 rabbits was infected with P. aeruginosa for 24 hr. The animals then were divided randomly into five groups of ten each. Groups A, B, and C were treated as described. Group D received liposomes without tobramycin and Group E, hourly balanced salt solution. Significantly fewer Pseudomonas colonies were present in the corneas of all three drug-treated groups (A, B, and C) compared with the two control groups (D and E) at 24 hr (P less than 0.005). Significantly fewer Pseudomonas colonies were present in Groups A and B compared with Group C (P less than 0.02). No significant difference was noted between Groups A and B (P = 0.30). Tobramycin encapsulated in megaliposomes may be useful in treatment of pseudomonal keratitis.