A dose-finding study of duloxetine based on serotonin transporter occupancy.
BACKGROUND
Positron emission tomography (PET) has been utilized for determining the dosage of antipsychotic drugs. To evaluate the dosage of antidepressants such as selective serotonin reuptake inhibitors, serotonin transporter occupancy (5-HTT) is also a useful index.


OBJECTIVE
We investigated the degree of 5-HTT occupancy with different doses of the antidepressant duloxetine and the time-course of 5-HTT occupancy using PET.


METHODS
PET scans with [11C]DASB were performed before and after a single administration of duloxetine (5-60 mg), and three consecutive scans were performed after a single dose or repeated doses of 60 mg of duloxetine.


RESULTS
5-HTT occupancies by duloxetine were increased by 35.3 to 86.5% with dose and plasma concentration increments. The ED50 value of 5-HTT occupancy was 7.9 mg for dose and 3.7 ng/ml for plasma concentration. In the time-course of 5-HTT occupancy, mean occupancies were 81.8% at 6 h, 71.9% at 25 h, and 44.9% at 53 h after a single administration, and 84.3% at 6 h, 71.9% at 49 h, and 47.1% at 78 h after repeated administrations.


CONCLUSIONS
Based on 5-HTT occupancy, 40 mg and more of duloxetine was needed to attain 80% occupancy, and 60 mg of duloxetine could maintain a high level of 5-HTT occupancy with a once-a-day administration schedule.
Takano
Akihiro
A
Molecular Imaging Center, National Institute of Radiological Sciences, 9-1, Anagawa 4-Chome, Inage-ku, Chiba, 263-8555, Japan.
Suzuki
Kazutoshi
K
Kosaka
Jun
J
Ota
Miho
M
Nozaki
Shoko
S
Ikoma
Yoko
Y
Tanada
Shuji
S
Suhara
Tetsuya
T
D000328:Adult; D004305:Dose-Response Relationship, Drug; D000068736:Duloxetine Hydrochloride; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D049268:Positron-Emission Tomography; D050486:Serotonin Plasma Membrane Transport Proteins / Q000378:metabolism*; D017367:Selective Serotonin Reuptake Inhibitors / Q000008:administration & dosage* / Q000097:blood; D013876:Thiophenes / Q000008:administration & dosage* / Q000097:blood
D000068736:Duloxetine Hydrochloride; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors; D013876:Thiophenes