This study was conducted on 53 mature white male rats. A complex of morphological methods of the study was used in this scientific work, as well as biochemical analysis of blood serum. On the 7th day after Nalbuphine administration the lymphoid infiltration and swelling around portal triads, dilated and plethoric portal veins branches, uneven sinusoid capillaries with foci of erythrocyte stasis preliminary in the subcapsular area have been found. On the 14th day of the experiment the lobular structure of the liver was preserved, but cytoarchitectonics was disturbed in some areas. The hepatocytes in these areas were with hydropic dystrophy, their nuclei were uneven in shape and had the signs of swelling and hyperchromatism. These cells were placed chaotically. Mostly these changes were found in the 1-st zone of the classical liver lobule and in the subcapsular areas. Moreover, single monocellular and focal necrosis were found, as well as apoptosis. On the 21st day after Nalbuphine administration well-expressed changes of liver cytoarchitectonics, cells and microcirculation were found. The sinusoidal capillaries and venules were dilated, plethoric, with numerous erythrocytes, Kupffer cells, and leukocytes. Changes in hepatocytes are manifested in the form of dystrophy, apoptosis and monocellular necrosis. Most hepatocytes with changes were found in the subcapsular areas and in the 1st zones of the liver lobule. On the 28th day after Nalbuphine administration the liver cytoarchitectonics undergoes changes. In the marginal and subcapsular areas of all the examined specimens, the classical structure of the liver lobes was disturbed. The liver cells were located chaotically, and the radial direction of the cellular rows was absent. Beam structure with radial location of the liver cells is restored a little closer to the central veins. The classical structure of the liver lobes was completely preserved only deep in the parenchyma. The liver cells in the areas with disturbed cytoarchitectonics were round in shape with the signs of hydropic degeneration. More pronounced changes in the vessels were found in the rat`s liver after 35 days of Nalbuphine injection as well as in the stroma and parenchyma of the liver as compared to the previous terms of the study. Cytoarchitectonics of the liver was disturbed both in the subcapsular and marginal areas and in the first area of classical liver lobes, around the portal triads where numerous foci with the lack of cellular row structure were located. The majority of the liver cells in those foci were with degenerated and apoptotic changes. Pronounced lymphohistiocytic infiltration, hyperplasia, and hypertrophy of fibroblasts and collagen fibers were found in the foci of the liver cell necrosis. Pathological changes in the liver structure found during the previous terms increase in rats administered to 42 days of Nalbuphine injections. Cytoarchitectonics of the liver was disturbed in all the areas – absent clear beam structure, liver cells are often located chaotically or form separate fragments of the beams without clear radial direction. Pronounced lymphohistiocytic infiltration, hyperplasia, and hypertrophy of fibroblasts and collagen fibers were found in the foci of the liver cell necrosis. Monocellular and focal necrosis prevail. A great number of apoptotic changed cells was seen in all the field of vision. Key words: nalbuphine, opioid, liver, drug-abuse, rat. Branch-Medicine.
