Treatment-resistant OCD: There’s more we can do

Pharmacologic augmentation strategies

Selective serotonin reuptake inhibitors. While most OCD research trials have assessed SSRIs in 12-week studies, clinicians may consider extending SSRI treatment for an additional 12 weeks for nonresponders because some patients will continue to make gains. In the past, it was generally believed that higher doses of SSRIs are needed for treating OCD than for treating major depressive disorder. For instance, greater improvement was seen with 250 to 400 mg/d of sertraline compared with 200 mg/d²² and with escitalopram after an increase of dose up to 50 mg/d.²³ However, more recently, this notion of higher doses being necessary for treatment response has been called into question. For example, a study of escitalopram found similar responses to 10 mg/d vs 20 mg/d after 24 weeks.²⁴ A meta-analysis of adult studies of SSRIs for OCD supported higher doses as being more effective, but noted that the drop-out rate from treatment was greater in patients treated with higher doses.²⁵ As a note of caution, long-term, high-dose maintenance therapy increases the risk of adverse reactions.²⁶

Following a failed treatment with a first SSRI, it remains debatable as to what ought to be the second pharmacologic treatment. Although clomipramine is often reserved for treatment after 2 failed trials of an SSRI due to its greater risk of adverse effects, in an open-label study, switching from an SSRI to clomipramine led to greater response than switching from one SSRI to another.²⁷ On the other hand, while meta-analyses have reported greater treatment effect for oral clomipramine than for SSRIs, direct head-to-head comparisons have not supported this notion.²⁸ To get the best of both worlds, some clinicians employ a strategy of combining clomipramine with an SSRI, while monitoring for adverse effects and interactions such as serotonin syndrome.^29-31

Benzodiazepines. Although benzodiazepines are useful for brief treatment of an anxiety disorder (eg, for a person with a fear of heights who needs to take an airplane),³² they have not been shown to be effective for OCD³³ or as augmentation to an SSRI.³⁴

N-acetylcysteine (NAC). Two RCTs of adults with OCD who received adjunctive NAC, 3 g/d in divided doses, found no significant difference in the treatment arms by the conclusion of 16 weeks—either both groups improved, or both groups failed to improve.^35,36 In a 10-week study of patients with moderate to severe OCD symptoms, NAC, 2 g/d, as augmentation to fluvoxamine, 200 mg/d, showed a significant time x interaction in the treatment group.³⁷ No follow-up information is available, however.

In a multicenter RCT of NAC given to children and adolescents with OCD as augmentation to citalopram, symptoms decreased and the quality-of-life score improved, with a large treatment effect size in the NAC group.³⁸ However, in a study aimed at examining NAC in youth with Tourette syndrome, OCD symptoms were measured as a secondary outcome and there was no benefit of NAC over placebo.³⁹

Memantine. Four 8- to 12-week RCTs in adults with OCD favored adjunctive memantine, 20 mg/d, taken with an SSRI, over placebo.^40-43 A small study suggests that patients with OCD may be more likely to respond to memantine than patients with generalized anxiety disorder.⁴⁴ Case reports have noted that memantine has been beneficial for pediatric patients with refractory OCD.⁴⁵

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