The role of gentamicin iontophoresis in the treatment of burned ears.

Ear cartilage heals slowly, and limited vascularity in cartilage precludes use of systemic antibiotics. Iontophoresis electrically induces drugs in solution to migrate into target tissues. Fifteen patients were randomized to receive gentamicin iontophoresis (n = 7) plus dressing changes every 6 hours and cleaning or routine care alone (n = 8) for treatment of ear burns. There were no differences between the groups in incidence of chondritis (43% vs 50%) or cartilage loss (11% vs 16%). However, gentamicin-resistant organisms developed in 29% of the patients who received iontophoresis, but in none of the patients in the control group (p less than 0.05). To identify the etiology of the resistant organisms, 10 New Zealand white rabbits receive 7 cm2 contact burns to each ear. Gentamicin iontophoresis was performed on one ear, and the other ear served as the control. Serum gentamicin levels were always subtherapeutic. Additionally, gentamicin tissue levels in both the treated and control ears were subtherapeutic. Gentamicin iontophoresis appears to offer no additional salutary effects beyond those that are provided by routine care and may encourage the development of antibiotic resistance.