Effect of gamma radiation on the physicochemical properties of ciprofloxacin in solid state

Abstract

The aim of this study was to determine the effect of different doses of gamma irradiation on the physicochemical properties of ciprofloxacin (CF) in solid state as a model drug. Powder of CF has been subjected to different irradiation doses: 0, 15, 25, 50 and 100kGy from Cobalt-60 source in a Gammacell-220 at a rate of 1.15 Gray/s. The effect of radiation has been investigated using DSC, IR, spectrophotometric scanning and X-ray. The impact of irradiation on drug dissolution was also investigated. In addition, the irradiated samples were observed using scanning electron microscope (SEM). All irradiated samples showed chemical stability upon irradiation at the used irradiation doses. The DSC thermogram showed no change in the melting point (266°C) indicating that the CF identity existed. These findings were also supported by the existence of the ciprofloxacin principal absorption bands in the IR spectra at frequencies 1,616, 1,498 and 2,845 per cm for C=O stretching band of quinolone, C-N stretching band and N-C stretching band. The decrease in the enthalpy by increasing the dose of irradiation attributed the change in crystalline ciprofloxacin to a more amorphous form. The X-ray diffraction patterns of irradiated powder showed a lesser degree of crystallinity as evidenced by fewer peaks of lower intensity compared with the non-irradiated sample. The characteristics of diffraction peaks relevant to crystalline CF virtually disappeared by increasing the dose of radiation from 15 to 100kGy. This was also clearly demonstrated by SEM photomicrography. The rate of dissolution of CF samples was increased upon irradiation where irradiation at 100kGy dose showed the fastest dissolution rate while non-irradiated drug samples showed the slowest dissolution rate. It was also observed that CF powder changed in color with color intensity depending on the irradiation dose. Color change is suggested to be due to surface changes in powder samples. This was verified by spectrophotometric scanning of dissolved powder from both irradiated and non-irradiated samples where no trace of any peaks was noticed in the visible range indicating that no radiolytical intermediates responsible for color change were formed during the irradiation. Thus it could be concluded that, although there were important changes in CF powder physical properties upon exposure to different doses of irradiation, the drug was chemically stable.