Discontinue Lamotrigine and Continue Sertraline Monotherapy
You should discontinue the lamotrigine because it provided no therapeutic benefit on its own, and sertraline is the evidence-based first-line agent that is actually treating both the OCD and depression. 1
Why Sertraline is the Active Agent
Sertraline is a proven first-line treatment for OCD with demonstrated efficacy in multiple double-blind, placebo-controlled trials, showing significant superiority over placebo in reducing OCD symptoms at doses of 50-200 mg/day 2
SSRIs like sertraline are recommended as first-line agents for OCD due to their superior safety and tolerability profile compared to other options, with advantages for long-term treatment 1
For treatment-resistant depression with comorbid OCD, sertraline addresses both conditions simultaneously, making it the logical therapeutic foundation 3, 4
Why Lamotrigine Should Be Discontinued
Lamotrigine showed zero efficacy as monotherapy in this patient, indicating it is not contributing to the current response 1
Lamotrigine's evidence base for OCD is extremely weak: it is mentioned only as one of several glutamatergic agents with "some evidence of efficacy" in treatment-resistant OCD, far behind N-acetylcysteine and memantine which have stronger evidence 1
The only supporting evidence consists of isolated case reports 5, 6, which represent the lowest quality of evidence and cannot guide treatment decisions when a proven first-line agent (sertraline) is working
Lamotrigine can paradoxically induce OCD symptoms in patients with bipolar disorder, with obsessions and compulsions developing 2-8 months after initiation 7
The Clinical Logic is Clear
The patient's response timeline proves sertraline is the active agent: no improvement with lamotrigine alone, then improvement only after sertraline was added 1
Continuing an ineffective medication exposes the patient to unnecessary risks including potential drug interactions, side effects, and the documented risk of lamotrigine-induced obsessionality 7
Sertraline has demonstrated long-term efficacy and relapse prevention in OCD, with significantly lower rates of dropout due to relapse (9% vs 24% placebo) and acute exacerbation (12% vs 35% placebo) over 28 weeks 8
Evidence-Based Next Steps if Sertraline Alone is Insufficient
If sertraline monotherapy proves inadequate after discontinuing lamotrigine, the evidence-based augmentation strategies for treatment-resistant OCD are: antipsychotics (risperidone or aripiprazole), clomipramine, N-acetylcysteine, or memantine—not lamotrigine 1
The recommended maintenance duration for sertraline is minimum 12-24 months after achieving remission, with longer treatment often necessary due to relapse risk 1
Monitor for continued efficacy at 8-12 weeks after lamotrigine discontinuation to confirm sertraline monotherapy maintains the response 1