The manufacturer in the USA that received the Warning Letter uses purified water for the manufacture of an API intended for use in sterile drug products. The validation was criticised as well as the monitoring of the water system. In the course of a previous inspection it was observed that there have been repeatedly OOS results in the points: endotoxin and TOC (total organic carbon). According to the opinion of the FDA the endotoxin removal unit that was installed additionally has not been qualified adequately. Most interesting however is the criticism of the missing monitoring of the used source water. Here, the FDA missed a monitoring of the microbial and chemical qualities of the feed water, and the assurance that the purified water system is capable of consistently producing the required quality of purified water from the feed water.
For more detailed information please see the Warning Letter Original.