Restoration of CYP2D6 Inhibition and Full Remission of Obsessive-Compulsive Symptoms: A Case-Oriented Review

Background: Comorbid obsessive-compulsive symptoms in bipolar disorder often prove highly resistant to standard treatments, with serotonergic agents carrying substantial risk of mood destabilisation. Recent interest has focused on glutamatergic modulation as an alternative pathway, inspired by the rapid effects of ketamine, though oral regimens require careful attention to pharmacokinetics for clinical success.Methods: This retrospective case report describes a 23-year-old woman with previously stabilised bipolar disorder who, following treatment discontinuation, presented with severe moral scrupulosity and compulsive reassurance-seeking refractory to mood stabilisation alone. In routine outpatient care, valproate was combined with dextromethorphan (NMDA antagonism) and piracetam (AMPA positive allosteric modulation), with subsequent addition of a mild CYP2D6 inhibitor (Deanxit). Progress was monitored through clinical interviews and standardized questionaires.Results: Dextromethorphan 30–45 mg nocte plus piracetam 600–1200 mg nocte on a background of valproate 500 mg produced only modest reduction in ruminations. Marked and sustained improvement—near-complete resolution of obsessive thoughts and reassurance-seeking, with PHQ-9 falling from 16 to 8 and GAD-7 from 19 to 7—occurred only after introduction of Deanxit 1 tablet nocte, providing CYP2D6 inhibition via melitracen.Discussion: The stepwise response pattern underscores the critical role of sustained dextromethorphan exposure in achieving therapeutic NMDA blockade sufficient to drive downstream AMPA-mediated plasticity. This observation aligns with emerging clinical experience suggesting that pharmacokinetic optimisation is essential for translating ketamine-like mechanisms into reliable oral efficacy, particularly in complex bipolar-OCD presentations where conventional options are limited.