It happens that the cover have not used the bottle or vial does not want to otsenivaetsya, as if glued. These, by the way, happens Vice versa and with a fresh, not yet opened glass or plastic bottle, having a screw cap with retaining its annular shoulder on the spout, which when opened should come off and does not come off, and the hand slips on the cover, even if there are notches. Help out a strip of sandpaper wrapped around the cap to increase friction: with the skin it unscrewed easily.