Relevance of red blood cell Lithium concentration in the management of Lithium-treated bipolar and unipolar disorders: a systematic narrative review.

Background: Despite a variability in response and a narrow therapeutic index, Lithium (Li) remains the gold standard treatment for bipolar disorders (BD), and a treatment of choice for unipolar disorders (UD). Red blood cell Li concentration (RBCLiC) and red blood cell/plasma Li ratio (LiR) have been studied in many areas of mood disorders (such as acute or chronic Li efficacy, adherence, side effects (SE), intoxication management) as well as in several research domains. This systematic review aims to synthesize the existing literature.