Influence of baseline QTc on sotalol-induced prolongation of ventricular repolarization in men and women

The extent of sotalol-induced QTc prolongation on the electrocardiogram, is variable among subjects and influenced by sex. However, the influence of baseline QTc on the extent of drug-induced QTc prolongation remains unclear. This was studied around peak plasma concentration in a large cohort of 376 healthy male and 614 healthy female subjects who received 80 mg of sotalol orally. Baseline QTc was 379 ± 16 ms in men and 393 ± 15 ms in women (P < .0001). The change in QTc from baseline was highly variable among both sexes and was greater in women than in men (26.5 ± 13.2 vs.13.0 ± 10.8 ms; P < .0001). The slope of the regression line between QTc on sotalol and baseline QTc did not significantly differ from unity in men and in women, indicating that the extent of QTc prolongation with sotalol was not influenced by baseline QTc. Assessing QTc after administration of an I_Kr blocker may be more important than measuring a baseline QTc.