Photoprotection of daunorubicin hydrochloride with sodium sulfite

Protection of 10(-4) M daunorubicin hydrochloride (DNRUB) solutions against photolytic degradation was investigated using sodium sulfite (SS). Photodegradation of the drug under fluorescent light was found to be accelerated at higher pHs, and the photoprotecting ability of SS (1.9 x 10(-3) M) increased progressively with an increase in pH in the range of 3.7 to 8.2. Increase in ionic strength (mu) appeared to decrease the rate of degradation of the drug, in the presence or absence of SS, in acetate buffer (0.1 M) of pH 5.5. Photostability of DNRUB solutions was enhanced with an increase in SS concentration in pH 6.5 citrate buffer (0.1 M, mu = 0.5). The effect of various buffer species on the photostability of DNRUB was carried out using acetate, phosphate and citrate buffers. Divalent phosphate anion appeared to demonstrate the greatest catalyzing effect followed by trivalent citrate, combination of divalent and trivalent citrate (9:11 molar ratio), and monovalent acetate anion. Sodium sulfite was found to significantly diminish the catalyzing effect of all the buffers.