The pharmacokinetics of lisdexamfetamine dimesylate, a long-acting prodrug stimulant, and its active moiety, d-amphetamine, including dose-proportionality and variability, were assessed in 20 healthy adults. Subjects received a single dose, sequentially, of 50, 100, 150, 200, and 250 mg of lisdexamfetamine dimesylate. Plasma lisdexamfetamine dimesylate and d-amphetamine were measured before dosing and 0.25 to 96 hours postdose. Dose-proportionality and intersubject and intrasubject variability of pharmacokinetic parameters were examined. Safety assessments included adverse events. All 20 subjects received 50 and 100 mg while 18, 12, and 9 subjects received 150, 200, and 250 mg of lisdexamfetamine dimesylate, respectively. Ten subjects were discontinued during the study for prespecified stopping rules (2 consecutive hourly readings of blood pressure: systolic >160 mm Hg or diastolic >100 mm Hg). Mean maximum observed plasma concentration (C(max)) and area under the concentration-time curve from time 0 to infinity (AUC(0-∞)) increased linearly and dose-dependently for d-amphetamine. Median time to C(max) ranged from 4 to 6 hours for d-amphetamine and 1.0 to 1.5 hours for lisdexamfetamine dimesylate. Intersubject and intrasubject variability over doses from 50 to 150 mg was low (<20%) for both C(max) and AUC(0-∞). Adverse events included nausea, dizziness, headache, psychomotor hyperactivity, and dysuria. These findings indicate that the pharmacokinetic parameters of d-amphetamine were dose-proportional and predictable over a wide range of lisdexamfetamine dimesylate doses.

BackgroundLisdexamfetamine 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.ObjectiveThis study aimed to describe the pharmacokinetics and safety of LDX and venlafaxine extended-release (VXR), alone or combined.Study DesignThe study was an open-label, two-arm, single-sequence crossover investigation with randomization to treatment sequence.Setting and ParticipantsThe study was conducted at two clinical study centres and included healthy adult males and females (18–45 years of age).InterventionThe 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 MeasuresOn 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).ResultsAmong 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 p...

BackgroundIn clinical practice, α2-adrenoceptor agonists have been adjunctively administered with psychostimulants for the treatment of attention-deficit/hyperactivity disorder (ADHD). Two studies have examined the adjunctive use of guanfacine extended release (GXR, Intuniv®; Shire Development LLC, Wayne, PA, USA) with psychostimulants in children and adolescents with a suboptimal response to psychostimulant treatment. However, the potential for pharmacokinetic drug–drug interactions (DDIs) between GXR and lisdexamfetamine dimesylate (LDX, Vyvanse®; Shire US LLC, Wayne, PA, USA) has not been thoroughly evaluated.ObjectiveThe primary objective of this study was to examine the pharmacokinetics of GXR 4 mg and LDX 50 mg given as single doses alone and in combination.Study DesignThis was an open-label, randomized, three-period crossover, DDI study.SettingThe study was conducted in a single clinical research center.ParticipantsForty-two healthy adults were randomized in this study.InterventionsSubjects were administered single oral doses of GXR 4 mg, LDX 50 mg, or GXR and LDX in combination.Main Outcome MeasuresBlood samples collected predose and up to 72 h postdose assessed guanfacine, LDX, and d-amphetamine levels. Bioequivalence was defined as the 90 % confidence intervals (CIs) of the geometric mean ratios of the area under the plasma concentration–time curve extrapolated to infinity (AUC0–∞) and maximum plasma concentration (Cmax) falling within the bioequivalence reference interval (0.80–1.25). Safety measures included adverse events, vital signs, and electrocardiograms (ECGs).ResultsForty subjects completed the study. Following administration of LDX alone or in combination with GXR, the statistical comparisons of the AUC0–∞ and Cmax of d-amphetamine fell entirely within the reference interval. For guanfacine, the 90 % CI of the geometric mean ratio of AUC∞ for the two treatments was within the bioequivalence criteria, but for Cmax the upper bound of the 90 % CI exceeded the standard range for bioequivalence by 7 %. This relatively small change is unlikely to be clinically meaningful. Treatment-emergent adverse events (TEAEs) were reported by 42.9 % of subjects; the most commonly reported TEAEs included dizziness (5.0, 7.3, and 7.3 %) and headache (7.5, 4.9, and 7.3 %) following administration of GXR, LDX, and GXR and LDX in combination, respectively. Clinically significant ECG abnormalities occurred in one subject following administration of LDX and in one subject following coadministration of GXR and LDX.ConclusionsIn healthy adults, coadministration of GXR and LDX did not result in a clinically meaningful pharmacokinetic DDI compared with either treatment alone. No unique TEAEs were observed with coadministration of GXR and LDX compared with either treatment alone.

Neither therapeutic nor supra-therapeutic doses of guanfacine prolonged QT interval after adjusting for heart rate using individualized correction, QTcNi, through 12 hours postdose. Guanfacine does not appear to interfere with cardiac repolarization of the form associated with pro-arrhythmic drugs.

These results indicate that guanfacine causes a stabilizing effect on cardiac restitution that helps reconcile the clinical evidence for a lack of arrhythmia liability despite apparent increases in typical QT/QTc prolongation measures.