Lyophilization: An emerging trend in formulation of parenterals

Most often drugs in solution forms are susceptible to degradation and thus have reduced stability and shelf life. Gelsiation also known as Cryodessication or lyophilization is a well-established process that helps in improving the stability of labile pharmaceuticals. It is one of the recent emerging techniques for formulation of powder for injection. Many of the antibiotics, e.g., semi-synthetic penicillins, cephalosporins, doxycycline and chloramphenicol are manufactured by lyophilization process. Other drugs such as hydrocortisone sodium succinate, methylprednisolone sodium succinate and anti-cancer drugs are also formulated as lyophilized products. It involves sublimation of ice from the frozen product at low temperature and pressure resulting in a low water content which in turn helps in decelerating the physical, chemical and biological degradation reactions. Apart from enhancing the stability of the product, lyophilized formulations have several advantages, such as fast reconstitution, easy to handle during storage and shipping etc. However, the lyophilization of parenterals is not problem free. Rejection may be attributed to delay in reconstitution time, melt back or non-uniformity in color of the dried product. Since the process is cost intensive, optimization is important not only for saving the cost and time, but also to prevent rejection of the product. This article discusses design of lyophilization along with understanding the critical parameters that help in optimizing the process.