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. |
