Intervention: Paroxetine
Trial phase: Phase 2
ATC code: N06AB05
SMILES: Fc1ccc([C@@H]2CCNC[C@H]2COc2ccc3c(c2)OCO3)cc1
Sex: All
Age groups: Adult | Older Adult
Healthy volunteers: No
Participants at risk: 2
Group description: Paroxetine 20 milligrams (mg)/day once daily (OD) for 2 weeks; titration up to 50 mg/day OD if necessary to achieve sufficient response. The last dose level in the treatment phase was reduced stepwise by one step every week to the final dose level of paroxetine 20 mg/day as part of a taper phase.
Eligibility criteria:
Inclusion Criteria:

Patients who are primarily diagnosed with PTSD (Posttraumatic Stress Disorder: 309.81) using DSM-IV-TR criteria. The CAPS-DX (Clinician-Administered PTSD Scale-DX) and M.I.N.I. (The Mini International Neuropsychiatric Interview, Japanese version 5.0.0. [2003]) will be used for diagnosis
Pathologic condition: Patients who experienced a motor vehicle accident (MVA) with severe or potential severe physical injury more than 3 months ago but less than 12 months ago
Patients aged 20 and <65 at the time of signing the Informed consent
Male and female patients
Inpatient/outpatient status: Both are permitted
Patients who are able to give written informed consent in person (i.e., patients who are capable of giving written informed consent on their own)
Patients whose combined score of the CAPS-SX standard B, C, and D is over 50

Exclusion Criteria:

Patients primarily diagnosed with a DSM-IV-TR Axis I disorder other than PTSD (e.g. major depressive disorder, dysthymic disorder, specific phobia [simple phobia], obsessive-compulsive disorder, panic disorder, etc.) within 6 months of week -4 (start of baseline phase)
Patients presenting with a current major depressive episode that preceded the diagnosis of PTSD
Patients receiving disability payments due to PTSD or other psychiatric diseases
Patients currently engaged in compensation litigation whereby personal gain would be achieved from prolonged symptoms of PTSD or any other psychiatric disorders
Patients who meet the DSM-IV-TR criteria for substance abuse or dependence (alcohol or drugs) within 6 months of Week -4 (start of baseline phase)
Patients with history of a suicide attempt within 6 months before Week -4 (start of baseline phase), or have, in the opinion of the investigator, "C. high risk of suicide" according to the MINI at Week -4
Patients who are pregnant, lactating or of childbearing potential and are likely to become pregnant
Patients receiving electro-convulsive therapy (ECT) prior to Week -4 (start of baseline phase)
Patients receiving another investigational product within 12 weeks before Week -4 (start of baseline phase)
Patients with a history or complication of manic psychosis
Patients with a history or complication of convulsive disorder (epilepsy, etc.)
Patients with a diagnosis or complication of a cognitive disorder (MMSE <=24 points)
Patients with a history and complication of serious cerebral organic disorder. (e.g. cerebrovascular disorder, meningitis, degenerative disease and other neurological disorders and seizures; however, bleeding in the upper arachnoid membrane should not be excluded)
Patients unable or unwilling to undergo the fMRI procedure (e.g., cerebrovascular clipping surgery, pacemaker, any internal metals with magnetism, and claustrophobia)
Patients with glaucoma
Patients with a known tendency for bleeding or those with predisposing conditions
Patients with a history of hypersensitivity to paroxetine
Patients with serious physical symptoms (cardiac, hepatic and renal dysfunction, or hematopoietic dysfunction, etc.). For seriousness, Grade 3 of "Criteria for seriousness of adverse reactions to drugs, etc. (Yakuan No.80)" is used as an index
Patients with a history or complication of cancer or malignant tumour
Patients with chronic hepatitis type B and/or C which is positive of hepatitis B surface antigen (HBsAg) and/or hepatitis C antibody
Others whom the investigator or sub-investigator considers ineligible for or unable to participate in the investigation
Criteria at Week 0 (start of Treatment Phase):

Subjects whose drug compliance rate for Drug 1 (Run-in Phase placebo) is <80% between Week -4 and Week 0;

Subjects whose CAPS-SX total score of the standard B, C, and D at Week 0 varied by 25% or more compared with those at Week -2