title: Thresholds for the physiologic effects of adrenergic agents: a methodologic appraisal.
abstract: For hemodynamic responses to adrenergic agents, classical pharmacodynamic theory describes differences between agents in receptor specificity, potency and pharmacologic profile from derived parameters such as the ED50 or half-maximal concentration. However, pharmacodynamic parameters are derived exclusively from in vitro studies. We describe a method of analysis which permits derivation of the 'threshold' or minimum plasma drug concentration associated with discernible effects. The threshold is derived by graphic analysis of in vivo dose response data. We provide examples of both animal and human data which demonstrate agreement of experimental results with predicted responses. This approach permits more direct comparison of studies from different investigators, from different patient or diagnostic categories or at different developmental ages.
authors.affiliation: Department of Pediatrics, Harbor-UCLA Medical Center, UCLA School of Medicine, Torrance.
authors.forename: J F
authors.initials: JF
authors.lastname: Padbury
authors.forename: D M
authors.initials: DM
authors.lastname: Habib
authors.forename: A M
authors.initials: AM
authors.lastname: Martinez
mesh_terms: D000322:Adrenergic Agonists / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D002648:Child; D004305:Dose-Response Relationship, Drug; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D007223:Infant; D012756:Sheep
chemical_list: D000322:Adrenergic Agonists