title: An interindividual variability in the sensitivity of atrioventricular node to diltiazem in patients with paroxysmal supraventricular tachycardia.
abstract: To study the sensitivity of atrioventricular (AV) node to diltiazem in seven patients with paroxysmal supraventricular tachycardia (PSVT), we analyzed the plasma concentration-response relationship of this Ca-antagonist using AH interval as an index for assessing its Ca channel blocking effect on the AV node after an IV infusion (0.4 mg/kg). The postdose AH intervals were prolonged compared with the baseline, and their percentage changes correlated significantly (P less than 0.01) with log-diltiazem concentrations in all patients. However, drug concentrations associated with a 20% prolongation of AH interval differed considerably among the patients (range; 65 to 260 ng/ml), indicating a large interindividual variability in the sensitivity of AV node to diltiazem. These results suggest that the interindividual difference in the responsiveness of AV node to diltiazem-induced Ca channel blocking effect may be one of the possible explanations for the therapeutic failure of this Ca-antagonist for terminating PSVT or preventing its recurrences in certain patients.
authors.affiliation: Department of Medicine, Second National Hospital of Tokyo, Division of Clinical Pharmacology, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Fukuhara
authors.forename: H
authors.initials: H
authors.lastname: Echizen
authors.forename: M
authors.initials: M
authors.lastname: Naito
authors.forename: S
authors.initials: S
authors.lastname: Ishikawa
authors.forename: M
authors.initials: M
authors.lastname: Toyama
authors.forename: H
authors.initials: H
authors.lastname: Nagoshi
authors.forename: M
authors.initials: M
authors.lastname: Honda
authors.forename: T
authors.initials: T
authors.lastname: Ishizaki
mesh_terms: D000328:Adult; D000368:Aged; D001283:Atrioventricular Node / Q000187:drug effects*; D004110:Diltiazem / Q000627:therapeutic use*; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D013614:Tachycardia, Paroxysmal / Q000188:drug therapy* / Q000503:physiopathology
chemical_list: D004110:Diltiazem