Paroxetine (Page 6 of 8)
13 NONCLINICAL TOXICOLOGY
13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility
Two-year carcinogenicity studies were conducted in rodents given paroxetine in the diet at 1, 5, and 25 mg/kg/day (mice) and 1, 5, and 20 mg/kg/day (rats). These doses are up to approximately 1.6 (mouse) and 2.5 (rat) times the MRHD on an mg/m2 basis. There was a significantly greater number of male rats in the high-dose group with reticulum cell sarcomas (1/100, 0/50, 0/50, and 4/50 for control, low-, middle-, and high-dose groups, respectively) and a significantly increased linear trend across dose groups for the occurrence of lymphoreticular tumors in male rats. Female rats were not affected. Although there was a dose-related increase in the number of tumors in mice, there was no drug-related increase in the number of mice with tumors. The relevance of these findings to humans is unknown.
Paroxetine produced no genotoxic effects in a battery of 5 in vitro and 2 in vivo assays that included the following: Bacterial mutation assay, mouse lymphoma mutation assay, unscheduled DNA synthesis assay, and tests for cytogenetic aberrations in vivo in mouse bone marrow and in vitro in human lymphocytes and in a dominant lethal test in rats.
Impairment of Fertility
Some clinical studies have shown that SSRIs (including paroxetine) may affect sperm quality during SSRI treatment, which may affect fertility in some men.
A reduced pregnancy rate was found in reproduction studies in rats at a dose of paroxetine of 15 mg/kg/day, which is approximately twice the MRHD on an mg/m2 basis. Irreversible lesions occurred in the reproductive tract of male rats after dosing in toxicity studies for 2 to 52 weeks. These lesions consisted of vacuolation of epididymal tubular epithelium at 50 mg/kg/day and atrophic changes in the seminiferous tubules of the testes with arrested spermatogenesis at 25 mg/kg/day (approximately 6 and 3 times the MRHD on an mg/m2 basis).
14 CLINICAL STUDIES
14.1 Major Depressive Disorder
The efficacy of paroxetine extended-release tablets as a treatment for major depressive disorder (MDD) was established in two 12-week, multicenter, randomized, double-blind, placebo-controlled, flexible dose studies with paroxetine extended-release tablets (Study 1 and Study 2) in adult patients who met Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV criteria for MDD. Study 1 and 2 included patients 18 to 65 years old who received paroxetine extended-release tablets doses of 25 to 62.5 mg/day (N = 212) or placebo (N = 211) once daily compared to immediate-release paroxetine 20 mg to 50 mg (N = 217). A third 12-week, multicenter, randomized, double-blind, placebo-controlled, flexible dose study with paroxetine extended-release tablets (Study 3) included elderly patients, ranging in age from 60 to 88 years old and used paroxetine extended-release tablets doses of 12.5 to 50 mg/day (N = 104) or placebo (N = 109) once daily compared to immediate- release paroxetine 10 mg to 40 mg (N = 106). In all three studies, paroxetine extended-release tablets were statistically superior to placebo in improving depressive symptoms as measured by the following: the mean change from baseline in the Hamilton Depression Rating Scale (HDRS) total score at Week 12, the mean change from baseline in the Hamilton Depressed Mood item score at Week 12, and the mean change from baseline in the Clinical Global Impression (CGI)–Severity of Illness score.
Long-term efficacy of paroxetine for treatment of MDD in outpatients was established with one randomized withdrawal study with immediate-release paroxetine. Patients who responded to immediate-release paroxetine (HDRS total score < 8) during an initial 8-week open-label treatment phase were then randomized to continue immediate-release paroxetine or placebo, for up to 1 year. Patients treated with immediate-release paroxetine demonstrated a statistically significant lower relapse rate during the withdrawal phase (15%) compared to those on placebo (39%). Effectiveness was similar for male and female patients.
14.2 Panic Disorder
The effectiveness of paroxetine extended-release tablets in the treatment of panic disorder (PD) was evaluated in three 10-week, multicenter, flexible-dose studies (Studies 4, 5, and 6) comparing paroxetine extended-release tablets (12.5 mg to 75 mg daily) to placebo in adult outpatients 19 to 72 years of age who met panic disorder (with or without agoraphobia) criteria according to DSM-IV. These trials were assessed on the basis of their outcomes on 3 variables: (1) the proportions of patients free of full panic attacks at Week 10; (2) change from baseline to Week 10 in the median number of full panic attacks; and (3) change from baseline to Week 10 in the median Clinical Global Impression Severity score. For Studies 4 and 5, paroxetine extended-release tablets were superior to placebo on 2 of these 3 variables. Study 6 failed to consistently demonstrate a statistically significant difference between paroxetine extended-release tablets and placebo on any of these variables.
For all 3 studies, the mean dose of paroxetine extended-release tablets for completers at Week 10 was approximately 50 mg/day. Subgroup analyses did not indicate that there were any differences in treatment outcomes as a function of age or gender.
Long-term maintenance effects of paroxetine in patients with PD were demonstrated in a randomized-withdrawal study using immediate-release paroxetine. Patients who were responders during a 10-week, double-blind trial (followed by a 3-month double-blind maintenance phase) of immediate-release paroxetine were re-randomized to continue immediate-release paroxetine or placebo in a 3-month, double-blind withdrawal phase. Patients randomized to immediate-release paroxetine were statistically significantly less likely to relapse than placebo-treated patients.
14.3 Social Anxiety Disorder
The efficacy of paroxetine extended-release tablets as a treatment for social anxiety disorder (SAD) was established, in part, on the basis of extrapolation from the established effectiveness of immediate-release paroxetine in the treatment of SAD. In addition, the effectiveness of paroxetine extended-release tablets in the treatment of SAD was demonstrated in one 12-week, multicenter, double-blind, flexible-dose, placebo-controlled study of adult outpatients with a primary diagnosis of SAD by DSM-IV criteria (Study 7). In Study 7, the effectiveness of paroxetine extended-release tablets (12.5 mg to 37.5 mg daily) compared to placebo was evaluated on the basis of (1) change from baseline in the Liebowitz Social Anxiety Scale (LSAS) total score at Week 12 and (2) the proportion of responders who scored 1 or 2 (very much improved or much improved) on the CGI Global Improvement score at Week 12.
In Study 7, paroxetine extended-release tablets demonstrated statistically significant superiority over placebo on both the change on LSAS total score at Week 12 and the CGI Improvement responder criterion at Week 12. For patients who completed the trial, 64% of patients treated with paroxetine extended-release tablets compared to 35% of patients treated with placebo were CGI Improvement responders at Week 12.
Subgroup analyses did not indicate that there were any differences in treatment outcomes as a function of gender. Subgroup analyses of studies utilizing the immediate-release formulation of paroxetine generally did not indicate differences in treatment outcomes as a function of age, race, or gender.
14.4 Premenstrual Dysphoric Disorder
The effectiveness of paroxetine extended-release tablets for the treatment of Premenstrual Dysphoric Disorder (PMDD) utilizing a continuous dosing regimen has been established in 2 placebo-controlled trials in female patients ages 18 to 46 (Studies 8 and 9 [N = 672]). Patients in these trials met DSM-IV criteria for PMDD. Of 1,030 patients including Study 10, who were treated with daily doses of paroxetine extended-release tablets 12.5 or 25 mg/day, or placebo continuously throughout the menstrual cycle for a period of 3 menstrual cycles, the mean duration of the PMDD symptoms was approximately 11 ± 7 years. Patients on systemic hormonal contraceptives were excluded from these trials. Therefore, the efficacy of paroxetine extended-release tablets in combination with systemic (including oral) hormonal contraceptives for the continuous daily treatment of PMDD is unknown.
The VAS score is a patient-rated instrument that mirrors the diagnostic criteria of PMDD as identified in the DSM-IV, and includes assessments for mood, physical symptoms, and other symptoms associated with PMDD. In Studies 8 and 9, 12.5 mg/day and 25 mg/day of paroxetine extended-release tablets were statistically significantly more effective than placebo as measured by change from baseline to Month 3 on the luteal phase VAS score.
In an additional study employing luteal phase dosing (Study 11), patients (N = 366) were treated for the 2 weeks prior to the onset of menses with 12.5 or 25 mg/day of paroxetine extended-release tablets or placebo for a period of 3 months. In this trial, 12.5 mg/day and 25 mg/day of paroxetine extended-release tablets, as luteal phase dosing, was statistically significantly more effective than placebo as measured by change from baseline to luteal phase VAS score at Month 3.
There is insufficient information to determine the effect of race or age on outcome in Studies 8, 9, 10, and 11.
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