[Allergenic impurities in medicinal preparations containing aminopenicillin. I. Ampicillin sodium].

High-performance liquid chromatography (HPLC) with gradient elution has been used for the determination of degradation products in pharmaceutical preparations containing sodium ampicillin. In all preparations resulting by lyophilization process, the degradation products amount, almost exclusively constituted of allergenic polymeric substances deriving from condensation reactions, is more than 10%. On the contrary, the sodium ampicillin prepared by precipitation in non aqueous solvents, only contains the 2% of polymeric impurities.