Neuromuscular effects of beta-adrenergic blockers and their interaction with skeletal muscle relaxants.

Abstract

Intra-arterial pronethalol and propranolol produced a short-lasting neuromuscular blockade in the soleus nerve-muscle preparation of the cat. Intravenous pronethalol and propranolol prevented repetitive potentials of the soleus nerve as well as twitch potentiation and fasciculations of the soleus muscle induced by intravenous succinylcholine, but potentiated neuromuscular blockade. MJ 1999 did not protect fully against succinylcholine stimulation. Curare, 200–350 μg./kg., intravenously produced partial-to-complete neuromuscular blockade which was potentiated by intravenous pronethalol or propranolol. No significant potentiation was induced with corresponding doses of MJ 1999. We conclude that the neuromascular effects of beta-adrenergic blockers are independent of their interaction with catecholamines. The prevention of succinylcholine-induced potentials is ascribed to a presynaptic effect of beta blockers which depends on the “local anesthetic‘’ activity of the drugs.