The purpose of this study was to evaluate the influence of gamma-irradiation and dry heat sterilisation on the properties of a bioadhesive
powder mixture containing
ciprofloxacin and its corresponding ocular minitablets. The molecular weight characteristics of drum dried waxy maize
starch (DDWM), employed as major component of the bioadhesive formulation, the decay kinetics of radicals, the rheological properties of the bioadhesive
polymers and the microbial activity of
ciprofloxacin were studied. The influence of the different sterilisation methods on the characteristics of the ocular minitablets was investigated by measuring the crushing strength, the friability, and the in vitro release of
ciprofloxacin from the minitablets. Finally, the clinical value of the selected sterilised minitablets was evaluated in seven healthy volunteers. Both sterilisation methods similarly affected the properties of the bioadhesive formulation by inducing stable radicals and decreasing the molecular weight of DDWM, although no changes in the microbiological activity of
ciprofloxacin were measured. An obvious influence of both sterilisation methods was observed in the in vitro release study. The crushing strength and friability of the minitablets were not significantly influenced by gamma-irradiation. Based on these data, gamma-irradiation was more adequate as sterilisation method for the bioadhesive ocular minitablets than dry heat sterilisation, because it affected the least the physical properties of the minitablets. Therefore, the gamma-sterilised minitablets were selected for an in vivo evaluation in seven volunteers. The concentration of
ciprofloxacin in the tear film remained above its MIC value for the most common ocular pathogens for at least 8 h. Consequently, the gamma-irradiated minitablets containing
ciprofloxacin can be considered as a promising formulation to treat bacterial
keratitis and
conjunctivitis.