INTERACTIONS BETWEEN SUXAMETHONIUM AND NONDEPOLARIZING NEUROMUSCULAR BLOCKING-DRUGS

Citation
Mfm. Braga et al., INTERACTIONS BETWEEN SUXAMETHONIUM AND NONDEPOLARIZING NEUROMUSCULAR BLOCKING-DRUGS, British Journal of Anaesthesia, 72(2), 1994, pp. 198-204
Citations number
35
Categorie Soggetti
Anesthesiology
ISSN journal
00070912
Volume
72
Issue
2
Year of publication
1994
Pages
198 - 204
Database
ISI
SICI code
0007-0912(1994)72:2<198:IBSANN>2.0.ZU;2-F
Abstract
In anaesthetized cats, we have confirmed that previously injected suxa methonium potentiates non-depolarizing neuromuscular blocking drugs wh ereas, when injected during the block, suxamethonium antagonizes the p aralysis. We have attempted to explain these interactions by studying the effects of suxamethonium on extracellularly recorded nerve ending waveforms that correspond to the ionic currents in the mouse triangula ris sterni isolated nerve-muscle preparation. The preparations were pa ralysed with mu-conotoxin (obtained from the cone snail), which is bel ieved to act by selectively blocking sodium channels in muscle, and wh ich therefore should not interfere with currents at the nerve endings. Suxamethonium, in concentrations of 0.5-300 mu mol litre(-1), produce d a concentration-dependent increase in the amplitude of the waveform corresponding to the inward calcium current evoked by a nerve impulse. This effect did not occur in the presence of tubocurarine, suggesting that suxamethonium, which is a nicotinic agonist, may have been actin g on a nicotinic receptor on the nerve endings that is coupled to the voltage-operated calcium channels. The inward calcium current is belie ved to be responsible for neurotransmitter (acetylcholine) release. It is concluded, therefore, that its enhancement by suxamethonium contri butes to the ability of this drug to reverse non-depolarizing block. S uxamethonium also exerted complex effects on the waveform correspondin g to the outward flowing calcium-activating potassium current at the n erve endings, but no effect was observed in this isolated nerve-muscle preparation that could obviously explain the ability of suxamethonium to potentiate subsequently injected non-depolarizing blocking drugs.