Sterility testing of antimicrobial-containing injectable solutions prepared in the pharmacy

The need for sterility testing of antimicrobial-containing injectable solutions is discussed and specific testing methods are described. Despite their antimicrobial activity, antimicrobial-containing injectable drug products are not necessarily self-sterilizing and can become contaminated. In addition to practicing aseptic technique, pharmacists must perform end-product sterility testing on intravenous solutions to ensure their sterility. The United States Pharmacopeia provides guidelines for the performance and validation of two sterility test methods: membrane filtration and direct transfer to culture media. Membrane filtration is the method of choice for sterility testing of many antimicrobial-containing injectable solutions. After the test article is filtered, the membrane is rinsed with sterile fluid to remove residual antimicrobial agent, cut into two portions, and immersed in two types of culture medium. Visible turbidity of a sample within the appropriate incubation period indicates the presence of a contaminating microorganism. Closed filtration systems minimize false-positive results. In the direct transfer method, samples of the test article are directly inoculated into vessels of culture media, and antimicrobial activity is eliminated by dilution or by deactivation with chemical or enzymatic agents. Sterility testing as well as aseptic technique is needed to ensure the sterility of antimicrobial-containing injectable solutions.