The effect of some ointment bases on the systemic absorption of tobramycin from various wound surfaces of burned patients

Three kinds of 0·2 per cent tobramycin ointment were prepared with tobramycin and 3 ointment bases (cream, polyethylene glycol and hydrophilic petrolatum), and applied to the various wound surfaces of 5 burned patients. The systemic absorptions of tobramycin were compared with the values of the tentative AUC (area under the curve of tobramycin blood level, μg.h/ml.g) until 12 hours after the applications, by determining tobramycin level in blood. Similar values of AUC from the cream and polyethylene glycol ointments were obtained, while that of hydrophilic petrolatum ointment was very low. The systemic absorption of tobramycin from the polyethylene glycol ointment was studied when the ointment was applied to the wound surfaces of 7 patients with partial-thickness bum, 9 patients with full-thickness burn and 6 patients with burn ulcer. The mean values of the tentative AUC of patients with partial-thickness burn, full-thickness burn and burn ulcer were found to be 0·06, 0·03 and 0·15, respectively. These results showed that cream and polyethylene glycol bases should be used carefully as a vehicle of tobramycin ointments because of the rapid systemic absorption of tobramycin from human burn wounds, especially burn ulcer.