An evaluation of the impact of oral magnesium lactate on the corrected QT interval of patients receiving sotalol or dofetilide to prevent atrial or ventricular tachyarrhythmia recurrence.
BACKGROUND
Intravenous magnesium reduces the QTc interval of patients receiving ibutilide. Whether oral magnesium can reduce the QTc interval associated with oral sotalol and dofetilide is not known. This study was undertaken to evaluate the impact of oral magnesium on the QTc interval and whether an inherent intracellular magnesium deficiency exists among patients with arrhythmias.


METHODS
Participants receiving sotalol or dofetilide for atrial or ventricular arrhythmias were randomized to receive magnesium l-lactate (504 mg elemental magnesium daily, Niche Pharmaceuticals, Roanoke, TX) or placebo for 48 hours. A 12-lead electrocardiogram (ECG) was obtained at baseline, 3 hours, and 51 hours after dosing to correspond to the Tmax after oral ingestion. The QTc interval was measured from the ECGs and compared between groups. Intracellular magnesium concentrations were determined by energy-dispersive x-ray analysis at baseline and 51 hours after dosing (Intracellular Diagnostics, Inc., Foster City, CA).


RESULTS
The QTc interval reductions from baseline were greater in the magnesium group than placebo at 3 and 51 hours (P = 0.015 and P < 0.001, respectively). Sixty-three percent of patients (regardless of experimental group) had baseline intracellular magnesium concentrations below the normal reference range of 33.9-41.9 mEq/IU, with an average level of 32.6 +/- 2.2 mEq/IU.


CONCLUSIONS
Oral magnesium l-lactate raises intracellular magnesium concentrations and lowers the QTc interval of patients receiving sotalol or dofetilide.
McBride
Brian F
BF
School of Pharmacy, University of Connecticut, Storrs, USA.
Min
Bokyung
B
Kluger
Jeffrey
J
Guertin
Danette
D
Henyan
Nickole N
NN
Coleman
Craig I
CI
Silver
Burton B
BB
White
C Michael
CM
D000284:Administration, Oral; D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage*; D001145:Arrhythmias, Cardiac / Q000503:physiopathology / Q000517:prevention & control*; D016009:Chi-Square Distribution; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D004562:Electrocardiography; D005260:Female; D006801:Humans; D019344:Lactic Acid / Q000008:administration & dosage*; D017616:Magnesium Compounds / Q000008:administration & dosage*; D008297:Male; D010627:Phenethylamines / Q000008:administration & dosage*; D012008:Recurrence; D013015:Sotalol / Q000008:administration & dosage*; D018709:Statistics, Nonparametric; D013449:Sulfonamides / Q000008:administration & dosage*; D016896:Treatment Outcome
D000889:Anti-Arrhythmia Agents; D017616:Magnesium Compounds; D010627:Phenethylamines; D013449:Sulfonamides; D019344:Lactic Acid; D013015:Sotalol; C063533:dofetilide