Acute phase histopathological study of spinally administered midazolam in cats

Midazolam may be a useful analgesic when administered intrathecally. Howeve r, neurotoxicity must be excluded. The purpose of this study was to investi gate whether spinally administered midazolam induces acute-phase histopatho logical or inflammatory reactions of the spinal cord. A lumbar laminectomy was performed on 40 cats, and their spinal cords were exposed Midazolam 10 mg (2 mL, n = 20 cats) or saline 2 mt (20 cats) was administered directly t o the spinal cord. At 1, 2, 4, or 6 h after the administration, cats were k illed, and the lumbar spinal cord was removed and fixed in 10% formalin. Hi stology was examined using light microscopy with hematoxylin and eosin stai ning. Both groups showed slight to moderate changes in the spinal cord, but no severe damage was observed. Inflammatory reactions were seen in only on e cat in the saline group with slight neutrophil infiltration. These change s were not different between the midazolam group and the saline group. In c onclusion, up to 6 h after direct exposure to midazolam, no acute histologi cal damage or inflammatory reaction of the spinal cord was seen in cats. Im plications: Spinally administered midazolam, even in large doses, does not cause acute neurotoxicity or inflammation of the spinal cord.