Abstract
AIMS: Paroxetine is a selective serotonin reuptake inhibitor (SSRI), approved for treatment of major depressive disorder and anxiety disorders. Some SSRIs are known to prolong the QT interval; however, clinical evidence to establish a lack of association between paroxetine and corrected QT interval (QTc) prolongation is limited. Therefore, this study aimed to characterize the relationship between paroxetine concentration and QT/QTc interval following therapeutic doses in healthy individuals. METHODS: This open-label, single-arm, dose-escalating concentration-QT study (NCT06065735) was performed in healthy adults (18-65 years) without a history of cardiac disease or pre-diagnosed mood disorder. Eligible individuals (n = 38) received paroxetine 20 to 60 mg QD for 1 week per dose level. Paroxetine plasma concentrations and electrocardiogram recordings were monitored over a 12 h period on Days 1 (baseline), 7 (20 mg), 14 (40 mg) and 21 (60 mg). RESULTS: Mean change from baseline in QTcF (ΔQTcF) fluctuated between -7.1 and +4.7 ms. However, diurnal variation was also observed without treatment. A linear regression model showed no clinically significant effect of paroxetine concentrations on ΔQTcF, with a weak slope of 0.0108 ms/ng/mL (90% CI: 0.01, 0.03) and maximum ΔQTcF of +0.42 ms (90% CI: -2.68, 3.52) at 60 mg QD, corresponding to a Cmax of 221.4 (95%CI: 179.6-272.8) ng/mL. Similarly, paroxetine did not affect the mean change in PR or QRS interval, or heart rate relative to baseline. CONCLUSIONS: Paroxetine does not prolong QTc interval in healthy individuals to any clinically meaningful extent at therapeutically relevant doses. This study supports the favourable cardiac safety profile of paroxetine.