Effects of trimethaphan and sodium nitroprusside on hydrolysis of succinylcholine in vitro.

The use of hypotensive agents in combination with succinylcholine may be necessary. Since trimethaphan has been reported to prolong the action of succinylcholine, the authors studied the abilities of trimethaphan and sodium nitroprusside to inhibit hydrolysis of succinylcholine by pseudocholinesterase in vitro. Trimethaphan was found to be a potent noncompetitive inhibitor of pseudocholinesterase (KI = 0.24 micronM). It could be calculated that a typical dose of trimethaphan would approximately double the duration of paralysis produced by the usual dose of succinylcholine. Nitroprusside had no inhibitory effect in vitro. It is concluded that nitroprusside is preferable when a hypotensive agent must be used in conjunction with succinylcholine.