What is the use-by date of Filtrum®?

According to the instructions, use-by date of Filtrum^® is 2 years. At the end of this time, taking the drug is prohibited. This is explained by several points:

• Hydrolytic lignin (active ingredient of Filtrum^®) refers to stable complex biopolymers. But it gradually starts destructing, i.e. losing its power and safety. But within the manufacturer's guaranteed use-by-date, Filtrum^® saves completely all its properties.
• The released and properly stored preparation is not biologically dangerous. When taking inside, it can not cause infection by any pathogen that has settled on its surface. But after the expiry date, its binding (adsorbing) ability can decrease, which slightly increases possible ineffective binding and releasing precipitated bacteria.