Abstract
Background: Excessively high doses of loperamide (of up to 792 mg/day) have recently been associated with reports of cardiac events. However, no data currently demonstrate a direct effect of high doses of loperamide on the occurrence of cardiovascular abnormalities. Objectives: This study aimed to assess the effects of loperamide on QT/corrected QT (QTc) intervals, electrocardiogram (ECG) morphology, and overall safety and tolerability at therapeutic and supratherapeutic exposures in healthy adults. Methods: This randomized, double-blind, 4-way-crossover study enrolled 65 healthy adults to receive loperamide 8 mg (therapeutic dose), loperamide 48 mg (supratherapeutic dose), moxifloxacin 400 mg (positive control), and placebo. Least square (LS) mean difference in change from baseline in Fridericia-corrected QT (ΔQTcF) intervals between loperamide (8 mg and 48 mg) and placebo with the 2-sided 90% CI was calculated for each time point. A noninferiority criterion of mean difference in ΔQTcF of 10 ms evaluated whether loperamide was noninferior to placebo. Treatment safety was assessed throughout the study. Results: Most participants were female (66.2%) and white (95.4%). The age was 36.4 years (SD 9.77). The highest upper limit of the 2-sided 90% CI for LS mean difference in ΔQTcF between loperamide and placebo was 3.39 ms for the therapeutic dose and 9.28 ms for the supratherapeutic dose of loperamide, which were below the 10 ms threshold, thereby demonstrating noninferiority of loperamide to placebo. There were no statistically significant morphologic ECG changes after loperamide administration. There were no deaths, serious adverse events, or severe treatment-emergent adverse events. Conclusion: Single-dose loperamide at therapeutic (8 mg) and supratherapeutic (48 mg) doses do not show evidence of QTc prolongation of clinical concern in healthy participants. No new safety findings were identified.