稀释后久置青霉素在干燥状态下相对稳定，遇湿加速分解。其水溶液不稳定，放置时间越长分解越多，不仅降低了药效，而且产生的致敏物质也增多。故青霉素应随用随配制，稀释后不宜久置，以保证疗效和减少不良反应。 与酸性或碱性药物同用青霉素在接近中性（ pH=6～ 7）溶液中较? Penicillin diluted for a long time in the dry state is relatively stable, wet accelerated decomposition. The instability of its aqueous solution, the longer the time to decompose more, not only reduces the efficacy, but also increased the number of sensitizers. Therefore, penicillin should be used with the preparation, should not be diluted for a long time to ensure efficacy and reduce adverse reactions. With acidic or alkaline drugs with penicillin in the near neutral (pH = 6 ~ 7) solution more?