Lopitrast (Iopamidol), an organic Iodine compound and used as a non-ionic water-soluble radiographic contrast medium. Iopamidol blocks X-rays as they pass through the body, thereby allowing body structures not containing Iodine to be visualized. The degree of opacity produced by lopamidol is directly proportional to the total amount of the iodinated contrast agent in the path of the X-rays. The visualization of body structures is dependent upon the distribution and elimination of lopamidol.