Impact of Paroxetine, a Strong CYP2D6 Inhibitor, on SPN-812 (Viloxazine Extended-Release) Pharmacokinetics in Healthy Adults

Abstract

SPN-812 (viloxazine extended-release) is a novel nonstimulant recently approved as a treatment for attention-deficit/hyperactivity disorder in children and adolescents. Given that SPN-812 is metabolized by CYP2D6 and may be coadministered with CYP2D6 inhibitors, this trial investigated the pharmacokinetics and safety of SPN-812 coadministered with the potent CYP2D6 inhibitor paroxetine. In this single-sequence, 3-treatment period study in healthy volunteers, subjects received a single oral dose of 700 mg SPN-812 alone (period 1), 20 mg daily paroxetine (10 days, period 2), followed by concurrent administration of SPN-812 and paroxetine (period 3). Blood samples were collected for 72 hours post-SPN-812 dosing and analyzed for viloxazine and its primary metabolite, 5-HVLX-gluc. Twenty-two healthy adults were enrolled; all completed the trial. The potential for drug interaction between SPN-812 and paroxetine was assessed using analysis of variance on the log-transformed pharmacokinetic parameters Cmax, AUC0-t, and AUCinf. The least-squares geometric mean ratios for viloxazine were (reported as the ratio of combination/SPN-812 alone) Cmax, 116.04%; 90%CI, 109.49%-122.99%; AUC0-t, 134.65%; 90%CI, 127.65-142.03; and AUCinf, 134.80%; 90%CI, 127.94%-142.03%. CYP2D6 inhibition resulted in a modest change (<35%) on viloxazine AUCs with no change in Cmax. All adverse events were mild in severity.