Renal and Liver Disease:
Increased plasma concentrations of paroxetine occur in subjects with renal and hepatic impairment. The mean plasma concentrations in patients with creatinine clearance below 30 mL/min. were approximately 4 times greater than seen in normal volunteers. Patients with creatinine clearance of 30 to 60 mL/min. and patients with hepatic functional impairment had about a 2-fold increase in plasma concentrations (AUC, C ). max
The initial dosage should therefore be reduced in patients with severe renal or hepatic impairment, and upward titration, if necessary, should be at increased intervals (see ). DOSAGE AND ADMINISTRATION
In a multiple-dose study in the elderly at daily paroxetine doses of 20, 30, and 40 mg, C concentrations were about 70% to 80% greater than the respective C concentrations in nonelderly subjects. Therefore the initial dosage in the elderly should be reduced (see ). min min DOSAGE AND ADMINISTRATION
drug interaction studies reveal that paroxetine inhibits CYP2D6. Clinical drug interaction studies have been performed with substrates of CYP2D6 and show that paroxetine can inhibit the metabolism of drugs metabolized by CYP2D6 including desipramine, risperidone, and atomoxetine (see ). In vitro PRECAUTIONS ─ Drug Interactions
The efficacy of paroxetine tablets as a treatment for major depressive disorder has been established in 6 placebo-controlled studies of patients with major depressive disorder (aged 18 to 73). In these studies, paroxetine tablets were shown to be significantly more effective than placebo in treating major depressive disorder by at least 2 of the following measures: Hamilton Depression Rating Scale (HDRS), the Hamilton depressed mood item, and the Clinical Global Impression (CGI)-Severity of Illness. Paroxetine tablets were significantly better than placebo in improvement of the HDRS sub-factor scores, including the depressed mood item, sleep disturbance factor, and anxiety factor.
A study of outpatients with major depressive disorder who had responded to paroxetine tablets (HDRS total score <8) during an initial 8-week open-treatment phase and were then randomized to continuation on paroxetine tablets or placebo for 1 year demonstrated a significantly lower relapse rate for patients taking paroxetine tablets (15%) compared to those on placebo (39%). Effectiveness was similar for male and female patients.
The effectiveness of paroxetine tablets in the treatment of obsessive compulsive disorder (OCD) was demonstrated in two 12-week multicenter placebo-controlled studies of adult outpatients (Studies 1 and 2). Patients in all studies had moderate to severe OCD (DSM-IIIR) with mean baseline ratings on the Yale Brown Obsessive Compulsive Scale (YBOCS) total score ranging from 23 to 26. Study 1, a dose-range finding study where patients were treated with fixed doses of 20, 40, or 60 mg of paroxetine/day demonstrated that daily doses of paroxetine 40 and 60 mg are effective in the treatment of OCD. Patients receiving doses of 40 and 60 mg paroxetine experienced a mean reduction of approximately 6 and 7 points, respectively, on the YBOCS total score which was significantly greater than the approximate 4-point reduction at 20 mg and a 3-point reduction in the placebo-treated patients. Study 2 was a flexible-dose study comparing paroxetine (20 to 60 mg daily) with clomipramine (25 to 250 mg daily). In this study, patients receiving paroxetine experienced a mean reduction of approximately 7 points on the YBOCS total score, which was significantly greater than the mean reduction of approximately 4 points in placebo-treated patients.
The following table provides the outcome classification by treatment group on Global Improvement items of the Clinical Global Impression (CGI) scale for Study 1.
|Outcome Classification (%) on CGI – Global Improvement Item for Completers in Study 1|
|Outcome Classification||Placebo ( n = 74 )||Paroxetine Tablets USP , 20 mg ( n = 75 )||Paroxetine Tablets USP , 40 mg ( n = 66 )||Paroxetine Tablets USP , 60 mg ( n = 66 )|
|Very Much Improved||7%||7%||20%||20%|
The long-term maintenance effects of paroxetine tablets in OCD were demonstrated in a long-term extension to Study 1. Patients who were responders on paroxetine during the 3-month double-blind phase and a 6-month extension on open-label paroxetine (20 to 60 mg/day) were randomized to either paroxetine or placebo in a 6-month double-blind relapse prevention phase. Patients randomized to paroxetine were significantly less likely to relapse than comparably treated patients who were randomized to placebo.
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