title: On the simultaneous action of two competitive antagonists.
abstract: 1 A hypothesis is outlined predicting the conditions in which the addition of a second competitive antagonist will increase rather than reduce the response to an agonist.2 Experiments were performed with the guinea-pig ileum as the test tissue, hexyltrimethyl ammonium as the agonist, benzilyltropine methiodide as the ;slow' antagonist and pentyltriethyl ammonium as the ;fast' antagonist.3 The results are consistent with the hypothesis, if the affinity constant for hexyltrimethyl ammonium is between 2.7 and 3.7 x 10(4)M(-1), if the dissociation time constant for the slow antagonist is greater than 10 min and if that for the fast antagonist is less than 10 seconds.
mesh_terms: D000818:Animals; D004058:Diffusion; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D004347:Drug Interactions; D004357:Drug Synergism; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D009119:Muscle Contraction; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D011955:Receptors, Drug; D014326:Tropanes / Q000494:pharmacology
chemical_list: D000644:Quaternary Ammonium Compounds; D011955:Receptors, Drug; D014326:Tropanes