Single-Dose and Steady-State Pharmacokinetics of Tomoxetine in Normal Subjects

A pharmacokinetic profile of tomoxetine, a selective norepinephrine uptake inhibitor, was developed in human volunteers following single and multiple oral administrations. Following the administration of a single 90‐mg oral dose of tomoxetine to four normal volunteers, the plasma half‐life was 4.3 ± 0.5 hours. Mean plasma clearance was 0.60 ± 0.14 L/Kg/hr, and the mean volume of distribution was 3.7 4pL 0.9 L/kg. Multiple doses of tomoxetine (20 mg bid and 40 mg bid) for seven days were administered to an additional seven subjects. The data appeared to have a bimodal distribution. The mean plasma half‐life determined following the last dose was 4.6 ± 0.5 hours in five subjects. The other two subjects, one at each dose level, demonstrated accumulation of tomoxetine occurring from the first to last dose where tomoxetine disappeared from plasma with a mean half‐life of 19 hours.