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CIMETIDINE AND RANITIDINE: A STUDY OF COMPETITIVE AND ION‐CHANNEL BLOCKADE IN THE TOAD ISOLATED RECTUS ABDOMINIS MUSCLE
Author(s) -
Gwee M. C. E.,
Cheah L. S.,
Shoon M. L.
Publication year - 1986
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1986.tb00946.x
Subject(s) - cimetidine , ranitidine , carbachol , endocrinology , chemistry , medicine , toad , blockade , antagonist , receptor
SUMMARY 1. Responses of the toad isolated rectus abdominis muscle to cumulative doses of carbachol were recorded in the absence or presence of varying concentrations of cimetidine or ranitidine. The corresponding cumulative log concentration‐response curves for carbachol were then plotted for each antagonist studied. 2. Cimetidine (1 mmol/1) produced a straight and parallel 1.8‐fold shift of the carbachol curve to the right of the corresponding control curve with no significant change in the maximal response. 3. Cimetidine, at doses of 2.5 mmol/1 and 5 mmol/1, and ranitidine, at doses of 0.1 mmol/1, 0.25 mmol/1 and 0.5 mmol/1, produced a concentration‐dependent and non‐parallel shift of the carbachol curve to the right of the corresponding control curve accompanied by a marked decline of maximal responses. 4. The results provide further evidence that ion‐channel block may be involved in the neuromuscular blockade produced by cimetidine or ranitidine, the latter being more potent in this respect. Competitive antagonism may also be partly responsible for cimetidine‐induced neuromuscular blockade, especially at lower drug concentrations.