Cardiovascular and Neuromuscular Effects of Org NC 45, Pancuronium, Metocurine, and d‐Tubocurarine in Dogs

We compared the cardiovascular and neuromuscular effects of Org NC 45 with those of pancuronium, metocurine, and d-tubocurarine in six dogs anesthetized with halothane. The ED90 (dose of drug which produced a 90% depression of twitch tension) of Org NC 45, pancuronium, metocurine, and d-tubocurarine was 14 ± 3, 22 ± 3, 63 ± 19, and 130 ± 19 μg/kg, respectively. All subsequent neuromuscular and cardiovascular effects were determined from a dose equal to 3 times the ED90 of muscle relaxant. Org NC 45, pancuronium, metocurine, and d-tubocurarine produced a neuromuscular blockade with a duration (time from relaxant administration until recovery of 50% of the original twitch tension) of 42 ± 2, 108 ± 10, 109 ± 21, and 100 ± 19 minutes, respectively. Org NC 45 caused no significant cardiovascular changes. Pancuronium increased heart rate, mean arterial blood pressure, cardiac output, and pulmonary wedge pressure, and it decreased systemic vascular resistance (p < 0.05). Although metocurine also increased heart rate and cardiac output (p < 0.05), mean arterial blood pressure and pulmonary wedge pressure did not change. d-Tubocurarine decreased all cardiovascular parameters except heart rate which increased significantly (p < 0.05). We conclude that Org NC 45 produces a neuromuscular blockade of shorter duration with fewer cardiovascular changes than that of pancuronium, metocurine, or d-tubocurarine.