In a reflection paper of 5 March 2008, the EMEA takes a stand on the preparation of water for injection (WFI) by means of reverse osmosis (RO).

According to the American pharmacopoeia, the USP, it is permissible to prepare WFI by means of RO. The EMEA does not share this opinion and gives many reasons for this in its new paper. One reason is that many volatile organic impurities in the feed water are too small to be separated by the membranes used. The main problem, however, are biofilms covering the membranes (also on the permeate side), which represent a source for further biological growth in the system as well as for endotoxins.

EMEA holds that, with the membranes used nowadays, it is not possible to validate a procedure ensuring an RO-prepared water of the same quality as WFI manufactured through distillation. Testing for all possible impurities is not feasible either, according to EMEA. So the Agency concludes - and confirms its previous opinion - that it is not yet possible to prepare WFI safely by means of reverse osmosis. Still, this door is not being closed once and for all. The EMEA sees its paper as a call for further discussion and, should technical innovations be developed that could dispel present concerns, rethink its point of view.

The original reflection paper can be found here:
http://www.emea.europa.eu/pdfs/vet/qwp/2827108en.pdf

Author:
Dr Robert Eicher
On behalf of the European Compliance Academy