Controlled-release penicillin complexes. High-performance liquid chromatography and assay.

High-performance liquid chromatographic assays for the controlled-release penicillin complexes benzathine-cloxacillin, benzathine-penicillin V, procaine-penicillin G, benethamine -penicillin G and benzathine-penicillin G are described. Reversed-phase ion-paired chromatography using related aqueous acetonitrile mobile phases enables both components of the complex to be determined simultaneously. The utility of the methods is demonstrated by application to various formulations including fortified injections, which contain two complexes, and a suspension which also contains four preservatives.