In bipolar disorder, repurposed drugs are emerging as feasible augmentation options. Several agents, all sustained by a plausible biological rationale, have been evaluated. Evidence from meta-analyses showed that adjunctive allopurinol and tamoxifen were superior to placebo for mania, and add-on modafinil/armodafinil and pramipexole seemed to be effective for bipolar depression, while the efficacy of celecoxib and N-acetylcysteine appeared to be limited to certain outcomes. 
Further, meta-analytic evidence exists also for adjunctive melatonin and ramelteon in mania, and for add-on acetylsalicylic acid, pioglitazone, memantine, and inositol in bipolar depression, but findings were not significant. 
The generally low quality of evidence does not allow making reliable recommendations for the use of repurposed drugs in clinical practice, but some of these drugs have shown promising results and deserve further attention in research.