title: Effects of hypokalaemia on arrhythmogenic risk of quinidine in rats.
abstract: Plasma potassium concentration plays an important role in the induction of arrhythmia and is closely related to the arrhythmogenicity of various drugs. We quantitatively analyzed the influence of plasma potassium concentration on QT intervals before drug administration and on drug-induced QT prolongation, to estimate the risk of drug-induced arrhythmia under hypokalaemic conditions. The hypokalaemic models were produced by intraperitoneal administration of furosemide and hydrochlorothiazide in male Sprague-Dawley rats. The relationship between the changes in QT intervals and time profiles of plasma quinidine (QND) concentration were analyzed during constant intravenous infusion of QND (10 or 30 mg/kg/h) and post infusion in normal and hypokalaemic rats. The plasma QND concentration reached the therapeutic range (3-7 microg/ml) at the high infusion rate (30 mg/kg/h). No pharmacokinetic differences between normal and hypokalaemic rats were observed. QND induced QT prolongation in parallel with the plasma concentration without hysteresis. Although the potency of QND for QT prolongation was not affected by hypokalaemia, the QT intervals before drug administration were significantly prolonged in hypokalaemic rats (65.90 +/- 1.40 vs 56.60 +/- 0.748 msec, mean +/- SEM, p < 0.0001). Thus, the prolongation of QT intervals before drug administration may act as a risk factor of arrhythmia under hypokalaemic conditions.
authors.affiliation: Department of Pharmacy, The University of Tokyo Hospital, Faculty of Medicine, The University of Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hirota
authors.forename: H
authors.initials: H
authors.lastname: Ohtani
authors.forename: E
authors.initials: E
authors.lastname: Hanada
authors.forename: H
authors.initials: H
authors.lastname: Kotaki
authors.forename: Y
authors.initials: Y
authors.lastname: Sawada
authors.forename: T
authors.initials: T
authors.lastname: Iga
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects* / Q000493:pharmacokinetics; D001145:Arrhythmias, Cardiac / Q000139:chemically induced* / Q000378:metabolism / Q000503:physiopathology; D004562:Electrocardiography; D006321:Heart / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D007008:Hypokalemia / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology; D007262:Infusions, Intravenous; D008297:Male; D009206:Myocardium / Q000378:metabolism; D011188:Potassium / Q000097:blood; D011802:Quinidine / Q000009:adverse effects* / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012307:Risk Factors; D012964:Sodium / Q000097:blood
chemical_list: D000889:Anti-Arrhythmia Agents; D012964:Sodium; D011802:Quinidine; D011188:Potassium