Pharmacological Intensification Strategies in Highly Refractory Obsessive–Compulsive Disorder: Evidence Synthesis and a Tertiary-Care Case Series

Background: Treatment-resistant obsessive–compulsive disorder (TR-OCD) remains a major therapeutic challenge. Although current guidelines recommend optimized serotonin reuptake inhibitor (SRI) therapy, clomipramine switching, exposure and response prevention, and antipsychotic augmentation, a substantial proportion of patients continue to experience severe and disabling symptoms. In such cases, clinicians may consider pharmacological intensification strategies beyond guideline-endorsed algorithms. Methods: This study combines a structured narrative synthesis of pharmacological strategies for TR-OCD with a retrospective observational case series from a tertiary OCD referral clinic. Treatment resistance was defined as failure to achieve at least a 35% reduction in Yale–Brown Obsessive Compulsive Scale (Y-BOCS) score after at least two adequate SRI trials, including clomipramine, and optimized exposure and response prevention when available. Five patients treated with pharmacological intensification strategies were included. The primary outcome was percentage change in Y-BOCS score at 12 weeks. Results: The case series illustrates five strategies used in highly refractory OCD: supratherapeutic SSRI dosing, SSRI plus mirtazapine augmentation, dual SSRI therapy, serotonergic intensification in a clozapine-treated patient, and glutamatergic/GABAergic augmentation with topiramate. Baseline Y-BOCS scores ranged from 28 to 32. At 12 weeks, symptom reduction ranged from 23% to 36%. One patient met criteria for response, three showed near-response, and one demonstrated partial improvement. No cases of serotonin toxicity or clinically significant cardiac complications occurred. Conclusions: These cases suggest that carefully monitored pharmacological intensification may be feasible in selected specialist settings, but efficacy and safety require confirmation in prospective controlled studies. Recommendations: Pharmacological intensification should be reserved for highly refractory patients managed in specialist services, implemented with gradual titration, structured serotonin toxicity and electrocardiographic monitoring, and explicit individualized risk–benefit discussion; dual SSRI therapy should be regarded as the most experimental and highest-risk serotonergic option; and prospective controlled studies incorporating standardized functional outcomes are needed to refine patient-selection criteria and clarify which patients may benefit.