Background/Objectives: Bipolar disorder affects about 40 million people worldwide, and the greatest burden of the disease is associated with depressive episodes. About 25% of patients experience drug-resistant depression, in which standard treatment turns out to be insufficient, and monotherapy often does not bring full remission. Despite the use of second-generation antipsychotics, the effectiveness of therapy in TRBD remains limited, which necessitates rational polypharmacotherapy and augmentation strategies. The paper discusses the receptor mechanisms of drug combination, current therapeutic regimens and new interventions such as ketamine acting on the glutamate anergic system. The aim was to synthetically compare the efficacy and safety of available augmentation strategies and polypharmacotherapy. Methods: The material consists of published clinical, observational and randomized trials on pharmacotherapy of drug-resistant bipolar depression, including atypical neuroleptics, ketamine, pramipexole, modafinil, lamotrigine, celecoxib and memantine. The authors analyze receptor mechanisms, neurobiological data and clinical trial results, comparing them with current definitions of TRBD according to ISBD and CINP. Biomarker data, such as the Systemic Immune-Inflammation Index, and the results of neuroimaging and metabolomic studies were also used in the work. Results: The analysis showed that atypical neuroleptics showed limited efficacy and high rates of side effects, while ketamine has the fastest and most pronounced antidepressant effect with a low risk of phase change. Pramipexole has shown promise in terms of long-term efficacy, but its use reduces the high risk of induction of mania and impulse control disorders. Celecoxib as an anti-inflammatory therapy significantly increased response and remission rates compared to escitalopram alone, and memantine showed only an early, short-term antidepressant effect. The results highlight that TRBD requires targeted polypharmacotherapy, with the most promising directions being glutamatergic modulation and anti-inflammatory therapies. Conclusions: Drug-resistant bipolar depression requires a departure from classical monotherapy in favor of rational, mechanistically justified polypharmacotherapy, targeting complex monoaminergic, glutamatergic and neuroinflammatory disorders. Available data indicate that ketamine has the greatest clinical potential among the current strategies, characterized by a rapid onset of action and a favorable safety profile compared to atypical neuroleptics or dopamine agonists. Modulation of inflammatory processes with the use of celecoxib also has promising results, which highlights the importance of biomarkers and personalization of therapy. However, further, large, and well-designed studies are needed to unambiguously determine optimal treatment strategies for TRBD and to verify the effectiveness of new pharmacological interventions.
Jucha et al. (Sat,) studied this question.