title: Clinical and electrophysiologic effects of calcium channel blockers in patients receiving ibutilide.
abstract: BACKGROUND
  Ibutilide is indicated for the acute termination of atrial fibrillation and atrial flutter. Recent work concludes that ibutilide activates a late inward sodium current that is blocked by nifedipine. Because calcium channel blockers are commonly used in patients with atrial fibrillation, it is important to exclude an antagonistic effect on ibutilide in the clinical setting.
  
  
  METHODS
  We performed a retrospective electrocardiographic (ECG) review of patients enrolled in 3 clinical trials of ibutilide (2 atrial fibrillation conversion protocols and 1 ventricular tachycardia suppression protocol) to determine clinical efficacy and ECG effects of ibutilide in patients receiving and not receiving calcium channel blockers. Calcium channel blockers were administered as clinically indicated. A meta-analysis of the effects of calcium channel blockers on the conversion efficacy of atrial fibrillation and atrial flutter by ibutilide was also performed for studies in the literature.
  
  
  RESULTS
  One hundred thirty patients were included in the ECG analysis (106 from atrial fibrillation protocols and 24 from the ventricular tachycardia protocol). Sixty-eight of the 130 patients were taking calcium channel blockers at the time of ibutilide administration. There were no differences in the QT or QTc intervals, conversion rate for atrial fibrillation or atrial flutter, or suppression of ventricular tachycardia between patients taking and not taking calcium channel blockers. In the meta-analysis of 4 studies, there was no difference in the conversion rates between patients taking (52%, n = 221) and not taking (45%, n = 402) calcium channel blockers (P =.09).
  
  
  CONCLUSIONS
  In the clinical setting, the concomitant use of calcium channel blockers does not alter the ECG effects or efficacy of ibutilide for the treatment of atrial or ventricular arrhythmias.
authors.affiliation: Virginia Commonwealth University/Medical College of Virginia, Richmond, Va 23298, USA. mwoodmd@pol.net
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wood
authors.forename: David M
authors.initials: DM
authors.lastname: Gilligan
authors.forename: Chris
authors.initials: C
authors.lastname: Brown-Mahoney
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Nematzadeh
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Stambler
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ellenbogen
mesh_terms: D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000037:antagonists & inhibitors / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000188:drug therapy* / Q000503:physiopathology; D001282:Atrial Flutter / Q000188:drug therapy* / Q000503:physiopathology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004347:Drug Interactions; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D019338:Polypharmacy; D012189:Retrospective Studies; D013449:Sulfonamides / Q000037:antagonists & inhibitors / Q000627:therapeutic use*; D017180:Tachycardia, Ventricular / Q000188:drug therapy* / Q000503:physiopathology
chemical_list: D000889:Anti-Arrhythmia Agents; D002121:Calcium Channel Blockers; D013449:Sulfonamides; C067192:ibutilide