title: Use of the logistic function for the calculation of dose-ratios and potency ratios.
abstract: 1 Dose-ratios and potency ratios, obtained with the guinea-pig isolated ileum by calculating matching concentrations from a least-squares fit using a logistic relationship between response and dose, differ from those obtained with the more usual assumption that response is a linear function of log dose over a limited range. 2 The differences are not due to the mathematical treatment of the results but arise from changes in sensitivity associated with the production of very high or very low responses. 3 With this preparation there is no advantage in avoiding the linear transformation and fitting the results to the complete dose-response curve though this might not apply to results obtained from other tissues with less variable sensitivity.
mesh_terms: D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008433:Mathematics; D004364:Pharmaceutical Preparations / Q000008:administration & dosage*; D010648:Phenylacetates / Q000494:pharmacology; D014326:Tropanes / Q000494:pharmacology
chemical_list: D004364:Pharmaceutical Preparations; D010648:Phenylacetates; D014326:Tropanes; D002217:Carbachol