Toxicodynamic analysis of cardiac effects induced by four cholinesterase inhibitors in rats

Koujirou Yamamoto, Miho Shimizu, Hisakazu Ohtani, Masahiro Hayashi, Yasufumi Sawada, Tatsuji Iga

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


The cardiac effect of edrophonium (2-20 μmol kg-1), pyridostigmine (0.5-5 μmol kg-1), neostigmine (0.05-0.5 μmol kg-1) and ambenonium (0.02-0.3 μmol kg-1) was investigated after intravenous administration to rats. For pyridostigmine and neostigmine, the heart rate decreased in a dose-dependent manner, and then gradually recovered to the basal level at about 10 min. Rapid decrease of heart rate was observed after edrophonium and ambenonium administration, and rapid recovery to the basal level within 1 min. For ambenonium, a dose-dependent tachycardiac response was observed. The time-course of heart rate change was analysed by the effect-compartment model. Significant correlation was observed between bradycardiac EC50 values obtained by effect-compartment model analysis and inhibitory constant (K(i)) to acetylcholinesterase in-vitro, suggesting that the bradycardiac response was induced by inhibition of this enzyme and following elevation of acetylcholine concentration in the synaptic cleft. On the other hand, the tachycardiac EC50 values of edrophonium and ambenonium based on the effect-compartment model analysis were similar to dissociation constants (K(d)) of these drugs to muscarinic receptors in-vitro, suggesting that the tachycardiac activity of these drugs may be associated with antagonistic activity to postsynaptic muscarinic receptors. We conclude that, clinically, edrophonium and ambenonium are safer drugs than pyridostigmine and neostigmine, at least as regards muscarinic side-effects, including bradycardia.

Original languageEnglish
Pages (from-to)935-939
Number of pages5
JournalJournal of Pharmacy and Pharmacology
Issue number9
Publication statusPublished - 1996 Sept
Externally publishedYes

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science


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