Pharmacokinetics and pharmacodynamics of the muscle relaxant drug Org NC-45 and each of its hydroxy metabolites in dogs.

The pharmacodynamics and pharmacokinetics of Org NC-45 and each of its metabolites were studied in anaesthetized dogs. Only Org NC-45 and C3-deacetylated NC-45 produced neuromuscular blockade at the doses studied. The plasma half-lives varied from 3 to 15 min, and are about one third of that of the structurally-related compound pancuronium. Renal excretion was of the order 5-20% and the biliary excretion 7-20% 6 h after administration of each of the 4 compounds. The apparent volume of distribution after a 1 1/2 h infustion was of the same order as the extracellular fluid volume. It seems that no significant entero-hepatic recirculation occurs. Thus, long term continuous infusions of Org NC-45 may be safe.