Tobramycin iontophoresis into corneas infected with drug-resistant Pseudomonas aeruginosa

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Abstract
Iontophoretic application of tobramycin was used to deliver drug to the cornea of rabbit eyes infected with a tobramycin-resistant strain of Pseudomonas aeruginosa (MIC = 31.25 .mu.g/ml). Corneas infected with P. aeruginosa 27853/pMG6 were treated 22 hours after infection with tobramycin delivered by either iontophroresis, mock iontophoresis (eye cup without current), or application of fortified topical drops. Corneal iontophoresis of tobramycin at 25 mg/ml caused more than a three log reduction in bacteria; yielding a significantly lower number of bacteria compared to untreated controls and all other treatments (P <EQ 0.0001). Corneal iontophoresis of tobramycin at 10 mg/ml showed a one log reduction in the number of bacteria per cornea, yielding a significantly lower number of bacteria compared to untreated controls (p .ltoreq. 0.0001), corneas treated with nine topical applications of 1.36% tobramycin drops (P .ltoreq. 0.0001), and corneas treated with mock iontophoresis (P .ltoreq. 0.02). These results suggest that iontophoresis is a powerful ocular delivery system for tobramycin and may be suitable for use with other chemotherapeutic agents.