Orexigen continues to seek approval for its fixed-combination of naltrexone on bupropion, Contrave.

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In contrast, a shorter QT interval was seen for the drug bupropion, even at higher doses.

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"Many of the neurotransmitters bupropion increases are involved in satiety -- you've eaten enough, " adds Kenny.

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The nonstimulant amantadine has been used to great advantage in treating ADD, as has bupropion (Wellbutrin) and the newest nonstimulant, Strattera.

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The two drugs are naltrexone, used to treat alcohol and cocaine addiction, and bupropion (known mainly as Wellbutrin), an antidepressant, which also helps people quit smoking.

CNN: Combo of old drugs offers new hope in obesity fight

Although bupropion isn't generally considered a first line treatment for depression during pregnancy, it might be an option for women who haven't responded to other medications or those who want to use it for smoking cessation as well.

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In one study, the average weight loss for a group taking a higher dose (32 mg) of naltrexone plus bupropion for about a year was 6.1% while for a lower dose (16 mg) it was 5%. (People taking a placebo had an average weight loss of 1.3%.) However, only half the participants who started the trial actually finished it.

CNN: Combo of old drugs offers new hope in obesity fight