[On the topical tolerance of aminoglycoside antibiotics--a prospective comparative cytomorphological study]

The local application of drugs is an efficient method for treating diseases of the external eye. However, some active substances can also cause a chronic toxic reaction at the ocular surface. No results from clinical experiments on the local tolerance of kanamycin which would meet the requirements of evidence-based medicine are as yet available.

Thus, the cytomorphological processes of the treatment with kanamycin were examined in a prospective randomised placebo-controlled double blind cross-over study. The effect of the topical application (5 times a day for 7 days) of Kanamycin POS® eye ointment on the conjunctival epithelial barrier was studied in comparison with an eye ointment base (placebo) in 25 healthy subjects. To detect cytopathological microchanges of the epithelium, we carried out a standardised impression cytology (primary compatibility parameter). Biomicroscopy, Schirmer II test and non-invasive measurement of the break-up-time (tearscope) were also examined. The subjective compatibility parameters (itching, tearing, foreign body sensation, burning sensation, mucus) were measured on a 0 - 10 visual analogue scale.

The cytological findings of 23 subjects were included in the final evaluation of the study. The impression cytology did not reveal a different effect of kanamycin ophthalmic ointment on the conjunctival ocular surface in comparison with the placebo. Only in one subject was a marked shift found in the nuclear-cytoplasmic ratio after application of verum. No signs of increased apoptosis ("snake-like chromatin") were found at the conjunctival epithelial barrier. The mean goblet cell count was 109 goblet cells per mm (2). No significant reduction of the goblet cell density was found in any treatment group. Among the subjective compatibility parameters, only the mean for itching constantly remained above the placebo group after application of kanamycin. Statistically significant differences were not found by the Wilcoxon test.

In contrast to the clinical experience with the systematic application of kanamycin, the standardised evaluation of this study confirmed the very good topical tolerability of the tested kanamycin eye ointment. In view of the continuing clinically relevant aspect of the availability of a wide spectrum of antibiotics to avoid the development of resistance while at the same time keeping within what is reasonable economically, Kanamycin POS® for topical application supplements the options of ophthalmological antibacterial chemotherapy.