An Open-Label Investigation of the Pharmacokinetic Profiles of Lisdexamfetamine Dimesylate and Venlafaxine Extended-Release, Administered Alone and in Combination, in Healthy Adults

BACKGROUND Lisdexamfetamine dimesylate (LDX), a prodrug consisting of d-amphetamine and l-lysine, is being studied in clinical trials of major depressive disorder. Additional drug-drug interaction studies were warranted. OBJECTIVE This study aimed to describe the pharmacokinetics and safety of LDX and venlafaxine extended-release (VXR), alone or combined. STUDY DESIGN The study was an open-label, two-arm, single-sequence crossover investigation with randomization to treatment sequence. SETTING AND PARTICIPANTS The study was conducted at two clinical study centres and included healthy adult males and females (18-45 years of age). INTERVENTION The study included two single-sequence crossover designs: LDX alone followed by LDX + VXR (Treatment Arm A); and VXR alone followed by VXR + LDX (Treatment Arm B). Drug treatment was initiated on day 1 with once-daily LDX or VXR alone with 15 days' titration to final dose (LDX 30, 50 and 70 mg for 5 days each; VXR 75, 150 and 225 mg for 5 days each). On days 16-30, VXR, titrated to a final dose of 225 mg, or LDX, titrated to a final dose of 70 mg, was coadministered for participants in Treatment Arm A or B, respectively. On days 31-38, VXR doses were tapered. MAIN OUTCOME MEASURES On days 1-2, 15-16 and 30-31, safety evaluations and blood samples were obtained pre-dose through 24 h post-dose for analysis of LDX, d-amphetamine, venlafaxine (VEN), and O-desmethylvenlafaxine (ODV). Combination treatment was considered bioequivalent to single treatment if 90 % confidence intervals (CIs) for geometric mean ratios (GMRs) of analytes fell within the interval 0.80-1.25 based on maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) from time zero to time of last measurable concentration (AUCτ). Safety assessments included treatment-emergent adverse events (TEAEs), pulse rate and blood pressure (BP), clinical laboratory assessments, and 12-lead electrocardiograms (ECG). RESULTS Among 80 enrolled subjects, 77 were included in pharmacokinetic and safety analyses. Combination LDX + VXR was bioequivalent to LDX alone, based on exposure to d-amphetamine (GMR [95 % CI], Cmax (ng/mL): 0.97 [0.82, 1.14], AUCτ: 0.95 [0.81, 1.12]). Exposure to VEN with LDX + VXR (vs. VXR alone) was increased (Cmax: 1.10 [0.88, 1.38], AUCτ: 1.13 [0.88, 1.45]) and ODV decreased (Cmax: 0.91 [0.77, 1.06], AUCτ: 0.83 [0.71, 0.96]), whereas composite VEN + ODV was bioequivalent to VXR alone (Cmax: 0.96 [0.84, 1.09], AUCτ: 0.98 [0.85, 1.13]). TEAEs with LDX or LDX + VXR were similar. Maximum mean increases from baseline were: pulse rate, +8.73 to 12.76 beats/min with either treatment alone and +17.67 to 20.85 beats/min with LDX + VXR; systolic BP, +4.32 to 6.56 mmHg with either treatment alone and +12.96 to 13.78 mmHg with LDX + VXR; diastolic BP, +5.39 to 5.74 mmHg with either treatment alone and +12.09 to 12.46 mmHg with LDX + VXR. One participant was withdrawn due to a serious TEAE (presyncope). No unexpected, clinically meaningful trends or changes from baseline in mean laboratory or ECG parameters were observed during the trial. CONCLUSION In healthy adults, combination LDX + VXR (vs. LDX alone) did not alter exposure to d-amphetamine. Although small changes in exposure to VEN (increased) and ODV (decreased) were seen with combination treatment, total VEN + ODV exposure showed no change (vs. VEN alone). LDX + VXR led to increases in BP and pulse rate, supporting existing recommendations for vital sign monitoring when using these medications.