title: [Effects of clinically available drugs on the repolarization process of the heart assessed by the in vivo canine models].
abstract: The proarrhythmic effects of class III antiarrhythmic agents and non-cardiovascular drugs, which have been shown to prolong QT interval, were assessed using two types of in vivo canine models. First, electrophysiological effects of dofetilide, nifekalant, amiodarone, cisapride, astemizole, sulpiride, haloperidol, and sparfloxacin were assessed using halothane-anesthetized dogs. Each drug prolonged the monophasic action potential (MAP) duration and effective refractory period (ERP) at clinically recommended daily doses. The extent of increase was greater in the refractoriness than in the repolarization only for amiodarone, indicating abbreviation of the terminal repolarization period. The reverse was true for the other drugs. Next, torsadogenic action of sematilide, nifekalant, amiodarone, cisapride, terfenadine, sulpiride, and sparfloxacin was assessed using chronic complete atrioventricular block dogs with Holter ECG monitoring in the conscious state. Oral administration of 1-10 times higher doses than the clinically relevant doses of the drugs induced polymorphic ventricular tachycardia torsades de pointes (TdP), except for amiodarone. These results indicate that the prolongation and backward shift of the terminal repolarization period may be closely related to the drug-induced TdP and suggest that these in vivo models can be used to screen proarrhythmic potential of new drugs.
authors.affiliation: Department of Pharmacology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Nakakoma-gun, Japan. atsushis@yamanashi.ac.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sugiyama
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects*; D014150:Antipsychotic Agents / Q000009:adverse effects; D000995:Antitubercular Agents / Q000009:adverse effects; D027682:Cation Transport Proteins; D020117:Cisapride / Q000009:adverse effects; D004195:Disease Models, Animal; D004285:Dogs; D051638:Ether-A-Go-Go Potassium Channels; D024841:Fluoroquinolones / Q000009:adverse effects; D005765:Gastrointestinal Agents / Q000009:adverse effects; D006220:Haloperidol / Q000009:adverse effects; D006634:Histamine H1 Antagonists / Q000009:adverse effects; D008133:Long QT Syndrome / Q000139:chemically induced*; D015221:Potassium Channels / Q000187:drug effects; D024642:Potassium Channels, Voltage-Gated; D013469:Sulpiride / Q000009:adverse effects; D016593:Terfenadine / Q000009:adverse effects; D016171:Torsades de Pointes / Q000139:chemically induced
chemical_list: D000889:Anti-Arrhythmia Agents; D014150:Antipsychotic Agents; D000995:Antitubercular Agents; D027682:Cation Transport Proteins; D051638:Ether-A-Go-Go Potassium Channels; D024841:Fluoroquinolones; D005765:Gastrointestinal Agents; D006634:Histamine H1 Antagonists; C092509:KCNH6 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D016593:Terfenadine; D013469:Sulpiride; D006220:Haloperidol; C061363:sparfloxacin; D020117:Cisapride