Investigations on the decomposition of carboplatin in infusion solutions II. effect of 1,1-cyclobutanedicarboxylic acid admixture

Eleven infusion solutions containing carboplatin (approximate to10 mg/ml) stored for 5 to 78 months at room temperature were investigated for the content of carboplatin and the profile of decomposition products by means of atomic absorption spectrophotometry (AAS) and high performance liquid chromatography (HPLC). Carboplatin loss was between 3.09% and 7.28%. Carboplatin degradation was exponential and depended only on the time of storage. For seven of the investigated products an admixture of 1,1-cyclobutane-dicarboxylic acid (CBDCA) (0.75%-2%) was shown. This admixture did not suppress the break-down of carboplatin, but changed the quantity of certain degradation products. Besides hydrophilic aqua- or hydro-xyplatinum(II)-species also hydrophobic side products were detectable. Especially in infusion solutions with CBDCA admixture a side product (SP) developed after the 55(th) week of storage. The peak area of this SP amounted to more than 1% of the peak area of carboplatin by the time of expiry.