The Neuromuscular Blocking Action Of Adreno- receptor Blockers, Pharmacological and clinical study.
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The results of the invitro experimental work revealed that esmolol ( 40,80 and 160 pig / ml) and phentolamine ( 100,200 and 400 pig / ml) caused reduction in toad's skeletal muscle contraction induced by acetylcholine, but both drugs failed to affect potassium chloride induced skeletal muscle contraction even in high concentration. However propranolol caused inhibition of both acetylcholine and potassium chloride induced skeletal muscle contraction in relatively lower concentrations ( 2,4,8,16,32, pig / ml ) . The invivo experimental work revealed that phentolamine, esmolol and propranolol reduced rat's gastrocnemius contractions but with relatively lower doses with propranolol. Also the three drugs potentiated the neuromuscular (N-M) blockade induced by d-tubocurarine ( DTC ) especially propranolol in low doses. In the clinical work neither esmolol nor labetalol affected the neuromuscular blocking action of pipecuronuim, with no significant differences in the recovery index ( T, 25% to T, 75%). In conclusion adrenoreceptor blockers ( especially B2 blokade ) can induce N-M blockade in animals, but not in man.