True statement regarding depolarizing neuro muscular blocking drugs
Correct Answer: All of the above
Description: (All of the above) (204-Lee's 12th) (340-43-KDT 6th)Features of non-depolarizing neuromuscular blocking drugs1 Do not cause muscular fasciculation2 Mostly mono- or bis-quatemary salts with interonium distance of 0.7-1.7 nm and high electrostatic characteristics i.e. very hydrophilic3 Relatively slow onset (1-58 min)4 Reversed by neostigmine and other anticholinesterases5 Effects reduced by adrenaline and acetylcholine: Also by suxamethonium (but not in myasthenics)6 The relaxed muscle is still responsive to other (mechanical and electrical) stimuli7 In partial paralysis, neuromuscular monitoring shows 'fade': post-tetanic facilitation followed by exhaustion, and depression of muscle twitch8 Potentiated by volatile agents, Mg++ and hypokalaemia.9 Slow dissociation constant at receptors10 Greater cooling (below about 33degC) potentiates them11 Mild cooling antagonizes their effects12 Repeated titanic bursts cause their effect to wear off13 Acidosis increases duration and degree of non-depolarizing blocks.Features of depolarizing (Phase I) neuromuscular blocking drugs1 Causes muscular fasciculation (but not in myasthenic humans and in some other species). Extraocular muscles exhibit a tonic response2 The depolarized muscle fibres are unresponsive to other stimuli. The Na+ channels are blocked open.3 Repolarization is interfered with the resting membrane potential is held up until phase II block develops. When it returns to - 70 mV.4 Not reversed by neostigmine and other anticholinesterases.5 In partial paralysis the neuromuscular monitoring shows depression of muscle twitch, no 'fade' but a well- sustained response, and no post-tetanic fascilitation.6 Potentiated by isoflurane, Enflurane, Ach, respiratory alkalosis, hypothermia and Mg++7 Antagonized by ether, halothane, acidosis, and non-depolarizing relaxants8 Fast dissociation constant at receptors. There is little or no bond between drug and receptors.9 Repeated or continuous use leads to 'phase II blocks"
Category:
Pharmacology
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