Miskowiak KW, Ehrenreich H, Kessing LV, Vinberg M.
J Clin Psychiatry. 2015 Jun;76(6):e835-6. doi: 10.4088/JCP.15lr09809a.
To the Editor: We thank Dr Lozano and colleagues for their comments on our study “Recombinant Human Erythropoietin to Target Cognitive Dysfunction in Bipolar Disorder: A Double-Blind, Randomized, Placebo-Controlled Phase 2 Trial,” which give us the opportunity to address some conceptually important points regarding the effects of erythropoietin (EPO) on cognition. Lozano et al note that it is a potential confound that patients remained on their mood-stabilizing treatment including lithium for the duration of the study for 2 reasons: first, lithium has dose-dependent procognitive effects in patients with amnestic mild cognitive impairment in doses from 150 mg to 600 mg but harmful effects on cognition at doses ≥ 1 g; second, lithium and EPO may activate similar signaling pathways and thus exert synergistic actions on neuroplasticity. Lozano et al point out that the EPO-associated improvement of cognition could have therefore been influenced by patients’ lithium treatment during or prior to the study and request (1) explicit data regarding lithium exposure for each study group and (2) analysis of whether EPO and lithium have independent cognitive effects, or whether the beneficial effects attributed to EPO could be partially due to lithium or an interaction between EPO and lithium … [see full reply in J Clin Psychiatry]