Scanning electron microscope images of insoluble particles of Subutex (left panel) and generic (right panel).

<p>A and F: solution before filtration; B–E and G–J: solution after cotton-filtration. B and G image (and inlay) were analysed after gold/paladium-coating. C–E and H–J: the magnification of the scanning microscope being varied from 250 to 2500 after carbon-coating.