Besides the abovementioned pharmacotherapies, various medications have been investigated in the treatment of GD patients. Bupropion has been used to treat various addictive disorders [
42,
43]. Dannon et al. conducted a blind-rater study comparing GD subjects taking naltrexone and bupropion, and reported that the efficacy of bupropion was similar to that of naltrexone [
44]. However, the first and only double-blind placebo-controlled trial examining bupropion showed that it was not superior to placebo in the treatment of GD [
45]. Olanzapine has been evaluated in two double-blind, placebo-controlled trials, but both studies failed to show differences between olanzapine and placebo in the treatment of GD [
46,
47]. In addition, Grant et al. reported the efficacy of as-needed ecopipam on GD patients in single-blind setting. However, more controlled studies are required to support this result [
48]. On the other hand, one study reported that haloperidol actually promoted gambling-related thoughts and behaviors [
49]. Zack and Poulos tested modafinil with GD patients in a double-blind, placebo-controlled setting [
50]. They reported that modafinil decreased motivation to gamble and risky decision making, and improved inhibitory control in high-impulsivity participants; however, it had opposite effects on low-impulsivity participants. Another analysis showed that modafinil might deter pathological gamblers from chasing losses but also encourage them to continue betting rather than quit while they are ahead [
51]. N-acetyl cysteine (NAC) was found to be effective in the treatment of GD patients in one open-label trial with a double-blind discontinuation period [
52]. However, there were some limitations to this study such as small sample size, short duration of treatment, and the fact that only responders were randomized into the double-blind portion of the study. One double-blind, placebo-controlled trial tested NAC in individuals with co-occurring nicotine dependence and GD who were receiving imaginal desensitization therapy for GD and found that NAC presented additional benefits at 3-month follow-up [
53]. Amantadine was shown to decrease GD symptoms among GD individuals with Parkinson’s disease in a double-blind, placebo-controlled trial [
54]. A recent study also reported that GD participants with Parkinson’s disease showed a decrease in risky choices and an increase in non-risky choices during amantadine treatment [
55]. On the other hand, another study found that amantadine use could be associated with GD in Parkinson’s disease patients [
56]. One open-label study tested memantine in GD patients and reported that memantine treatment was associated with diminished gambling and improved cognitive flexibility [
57]. However, this study provided limited evidence because of small sample size, short-term follow-up duration, and open-label setting. In two open-label trials, acamprosate has also been tested for GD patients. However, the result of each trial is conflicting [
58,
59]. The efficacy of most of these medications to treat GD has not yet been definitely confirmed. Some of them have proved to be effective in only specific situations. In addition, a few of them were even found to exacerbate the symptoms of GD. Therefore, clinicians should be careful when prescribing these medications to GD patients.