Reproducibility of QTc interval changes after meal intake

- The study investigated the reproducibility of QTc changes after meal intake.
- The results show that the intra-subject reproducibility of QTc changes after meal is poorer than the intra-subject reproducibility of heart rate changes after meal.
- The results further show that the inter-subject reproducibility of QTc changes after meal is poorer than the inter-subject reproducibility of QTc changes due to a single 400 mg dose of moxifloxacin.
- The study has implications for the proposal of using QTc changes after meal as an assay sensitivity test in thorough QT/QTc studies.

BackgroundDetection of QTc decreases after meal intake was proposed as a possible proof of assay sensitivity in studies of drug-induced QTc changes. However, day-to-day reproducibility of QTc decreases after meal intake has not been established.MethodsHolter recordings were available from 4 different baseline drug-free days of a thorough QT study in 157 females and 164 males. During each of the baselines, subjects were fasting in the morning and were served standardized lunch. Heart rates and QTc intervals were measured during repeated time-points throughout each study day. Two investigations were performed. In the first investigation, 3 heart rate and QTc measurements 1, 2, and 3 h after lunch were averaged in each subject and corrected for the morning fasting baseline. Reproducibility of heart rate and QTc changes after the meal on different days X and Y was assessed by normalized repeatability coefficients 2*|MX − MY|/|MX + MY|, where MX and MY are measurements in the same subject on days X and Y, respectively. These were compared for heart rate and QTc changes after meal for different pairs of baseline days. In the second investigation, 36 females and 41 males were considered who received moxifloxacin during the source thorough QT study. The QTc increases after moxifloxacin were expressed by averaging 3 time-point values and corrected for placebo QTc values measured 25 days apart. In the same subjects, QTc readings after lunch were also corrected for fasting baseline readings 25 days apart. QTc responses to moxifloxacin and to meal intake were compared.ResultsRepeatability of QTc decreases after meal was significantly (p < 0.0000001) poorer than that of heart rate increases after meal. Of the subjects receiving moxifloxacin during the study, 6% did not show QTc prolongation on moxifloxacin while 39% have not shown QTc shortening after lunch (p < 0.00001).ConclusionThe reproducibility of QTc changes after meal is limited. The power of proving QTc assay sensitivity by the detection of QTc changes after meal is poorer than the power of the standard moxifloxacin-based assay sensitivity.