14.1 Major Depressive Disorder

The efficacy of bupropion in the treatment of major depressive disorder was established with the immediate-release formulation of bupropion hydrochloride in two 4-week, placebo-controlled trials in adult inpatients with MDD and in one 6-week, placebo-controlled trial in adult outpatients with MDD. In the first study, the bupropion dose range was 300 mg to 600 mg per day administered in 3 divided doses; 78% of patients were treated with doses of 300 mg to 450 mg per day. The trial demonstrated the efficacy of bupropion as measured by the Hamilton Depression Rating Scale (HAMD) total score, the HAMD depressed mood item (item 1), and the Clinical Global Impressions-Severity Scale (CGI-S). The second study included 2 fixed doses of bupropion (300 mg and 450 mg per day) and placebo. This trial demonstrated the efficacy of bupropion for only the 450 mg dose. The efficacy results were significant for the HAMD total score and the CGI-S severity score, but not for HAMD item 1. In the third study, outpatients were treated with bupropion 300 mg per day. This study demonstrated the efficacy of bupropion as measured by the HAMD total score, the HAMD item 1, the Montgomery-Asberg Depression Rating Scale (MADRS), the CGI-S score, and the CGI-Improvement Scale (CGI-I) score.

A longer-term, placebo-controlled, randomized withdrawal trial demonstrated the efficacy of bupropion HCl sustained-release in the maintenance treatment of MDD. The trial included adult outpatients meeting DSM-IV criteria for MDD, recurrent type, who had responded during an 8-week open-label trial of bupropion 300 mg per day. Responders were randomized to continuation of bupropion 300 mg per day or placebo for up to 44 weeks of observation for relapse. Response during the open-label phase was defined as a CGI-Improvement Scale score of 1 (very much improved) or 2 (much improved) for each of the final 3 weeks. Relapse during the double-blind phase was defined as the investigator’s judgment that drug treatment was needed for worsening depressive symptoms. Patients in the bupropion group experienced significantly lower relapse rates over the subsequent 44 weeks compared to those in the placebo group.

Although there are no independent trials demonstrating the efficacy of bupropion hydrochloride extended-release tablets (XL) in the acute treatment of MDD, studies have demonstrated similar bioavailability between the immediate-, sustained-, and extended-release formulations of bupropion HCl under steady-state conditions (i.e., the exposures [C max and AUC] for bupropion and its metabolites are similar among the 3 formulations).

14.2 Seasonal Affective Disorder

The efficacy of bupropion hydrochloride extended-release tablets (XL) in the prevention of seasonal major depressive episodes associated with SAD was established in 3 randomized, double-blind, placebo-controlled trials in adult outpatients with a history of MDD with an autumn-winter seasonal pattern (as defined by DSM-IV criteria). Bupropion treatment was initiated prior to the onset of symptoms in the autumn (September to November). Treatment was discontinued following a 2-week taper that began during the first week of spring (fourth week of March), resulting in a treatment duration of approximately 4 to 6 months for the majority of patients. Patients were randomized to treatment with bupropion hydrochloride extended-release tablets (XL) or placebo. The initial bupropion dose was 150 mg once daily for 1 week, followed by up-titration to 300 mg once daily. Patients who were deemed by the investigator to be unlikely or unable to tolerate 300 mg once daily were allowed to remain on, or had their dose reduced to, 150 mg once daily. The mean bupropion doses in the 3 trials ranged from 257 mg to 280 mg per day. Approximately 59% of patients continued in the study for 3 to 6 months; 26% continued for <3 months, 15% continued for >6 months.

To enter the trials, patients must have had a low level of depressive symptoms, as demonstrated by a score of <7 on the Hamilton Depression Rating Scale-17 (HAMD17) and a HAMD24 score of <14\. The primary efficacy measure was the Structured Interview Guide for the Hamilton Depression Rating Scale, Seasonal Affective Disorders (SIGH-SAD), which is identical to the HAMD24. The SIGH-SAD consists of the HAMD17 plus 7 items specifically assessing core symptoms of seasonal affective disorder: social withdrawal, weight gain, increased appetite, increased eating, carbohydrate craving, hypersomnia, and fatigability. The primary efficacy endpoint was the onset of a seasonal major depressive episode. The criteria for defining an episode included: 1) the investigator’s judgment that a major depressive episode had occurred or that the patient required intervention for depressive symptoms, or 2) a SIGH-SAD score of >20 on 2 consecutive weeks. The primary analysis was a comparison of depression-free rates between the bupropion and placebo groups.

In these 3 trials, the percentage of patients who were depression-free (did not have an episode of MDD) at the end of treatment was significantly higher in the bupropion group than in the placebo group: 81.4% vs. 69.7%, 87.2% vs. 78.7%, and 84.0% vs. 69.0% for Trials 1, 2 and 3, respectively. For the 3 trials combined, the depression-free rate was 84.3% versus 72.0% in the bupropion and placebo group, respectively.