Tirilazad mesylate--effects of the 21-aminosteroid on the lymphoid system of laboratory animals: a comparison with the glucocorticoid methylprednisolone.

Four-week toxicity studies with the 21-aminosteroid tirilazad mesylate were conducted in Sprague-Dawley rats, beagle dogs, and cynomolgus monkeys to support development of the drug for use in various clinical syndromes of injury to the central nervous system of humans. As the immune system is involved in many of the obvious side effects of glucocorticoids used currently for this indication, particular attention was directed to the lymphoid system; results were contrasted with similar data from studies with methylprednisolone, a classical glucocorticoid. Administration of tirilazad mesylate to rats, dogs and monkeys for 4 weeks had no effects at the highest doses tested on parameters assessed, including absolute peripheral blood lymphocyte counts, thymus or adrenal weights, circulating levels of cortisol, or lymphocyte proliferation response to phytohemagglutinin-P. Germinal centers in lymphoid tissues from dogs given high doses of tirilazad contained small numbers of macrophages with vacuolated cytoplasm but no other changes; lymphoid tissues in rats and monkeys given tirilazad were morphologically normal. Administration of methylprednisolone for a similar duration in rats and dogs at high dose levels was associated with increased death rates due to bacterial infections, markedly decreased peripheral blood lymphocyte counts and weights of thymus and adrenal glands, and prominent lymphoid atrophy as well as decreased circulating levels of cortisol. Female dogs infused for 10 days with a high dose of methylprednisolone had depression of the in vitro proliferation response of peripheral blood lymphocytes to phytohemagglutinin-P.

Effect of repeated administration of tirilazad mesylate on healthy and endotoxemic calves: a pilot study.

Tirilazad mesylate (TM:U74006F), a nonglucocorticoid 21-aminosteroid (lazaroid), is beneficial in the treatment of experimentally-induced ischemic injury following brain and spinal cord trauma, subarachnoid hemorrhage, hypovolemic shock and endotoxemia. This study investigated the effects of TM following repeated administration in sixteen healthy and endotoxemic calves. Group A calves received TM 3 mg/kg IV; group B calves received Escherichia coli endotoxin in increasing doses (0.1 to 20 micrograms/kg IV); group C calves received TM and endotoxin and group D calves received sterile saline (10 mL). Endotoxin, TM and saline were given every eight hours for five days. Mild, transient tachypnea was observed following TM administration. The drug suppressed clinical signs of endotoxemia until larger doses of endotoxin were given. At necropsy no substantial lesions were observed in groups A and D. Groups B and C had lesions consistent with endotoxemia but only group C calves had evidence of abomasal and ruminal ulceration. Although TM may be of benefit in the treatment of endotoxemia, further studies are needed to determine the optimal dosage and potential side effects in the endotoxic bovine neonate.