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The N-methyl-d-aspartate (NMDA) receptor antagonist ketamine is the most effective antidepressant drug for patients with treatment-resistant major depressive disorder (MDD) or bipolar disorder (BD) (Krystal et al. 2013). A single subanesthetic dose (0.5 mg/kg) of ketamine produces rapid antidepressant effects in up to two-thirds of patients with MDD and BD, and this effect can last for 7 days or more (Krystal et al. 2013; Zarate et al. 2012). However, the biochemical pathways defining the differences between patients who respond to ketamine and those who do not are currently unknown.
We read with great interest the article entitled “d-serine plasma concentration is a potential biomarker of (R,S)-ketamine antidepressant response in subjects with treatment-resistant depression,” by Moaddel et al. (2014). d-Serine acts as an endogenous, obligatory co-agonist at the NMDA receptor, and in their study, the authors reported that plasma levels of d-serine in the ketamine responder group (3.02 ± …
Hashimoto, K. (2014). Blood d-serine levels as a predictive biomarker for the rapid antidepressant effects of the NMDA receptor antagonist ketamine. Psychopharmacology, 231(20), 4081-4082. https://dx.doi.org/10.1007/s00213-014-3735-7