In vitro comparison between the neuromuscular and ganglion blocking potency ratios of atracurium and tubocurarine.

Results from in vitro experiments, using the hypogastric nerve--vas deferens preparation, and the phrenic nerve--hemidiaphragm preparation of the guineapig, have been used to determine the separation between the neuromuscular and ganglionic blocking effects of atracurium and tubocurarine. Regression lines were used to calculate the concentrations of each drug (99% confidence limits) which would produce a 50% blockade (EC50) of ganglionic and neuromuscular transmission. The equipotent molar ratio, using EC50 values, for ganglionic/neuromuscular blockade was 48 for atracurium and 9.4 for tubocurarine.