Treatment augmentation strategies for OCD: A review of 8 studies

1. Naderi S, Faghih H , Aqamolaei A, et al. Amantadine as adjuvant therapy in the treatment of moderate to severe obsessivecompulsive disorder: a double-blind randomized trial with placebo control. Psychiatry Clin Neurosci. 2019;73(4):169-174. doi:10.1111/ pcn.12803

Numerous studies support the role of glutamate dysregulation in the pathophysiology of OCD. Cortico-striato-thalamo-cortical (CSTC) abnormalities play a major role in the pathophysiology of OCD as suggested by neuroimaging research studies that indicate glutamate is the fundamental neurotransmitter of the CSTC circuit. Dysregulation of glutamatergic signaling within this circuit has been linked to OCD. Patients with OCD have been found to have an increase of glutamate in the CSF. As a result, medications that affect glutamate levels can be used to treat patients with OCD who do not respond to first-line agents. In patients already taking SRIs, augmentation of glutamate-modulating medications can reduce OCD symptoms. As an uncompetitive antagonist of the N-methyl-d-aspartate (NMDA)-type glutamate receptor, amantadine has been proposed as 1 of these medications.

Naderi et al¹⁰ evaluated amantadine as augmentative therapy to fluvoxamine for treating patients with moderate to severe OCD.

Study design

• This 12-week, randomized, double-blind, placebo-controlled trial evaluated the efficacy and safety of amantadine as an augmentative agent to fluvoxamine in 106 patients age 18 to 60 with moderate to severe OCD.
• Participants met DSM-5 criteria for OCD and had a Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score >21. Participants were excluded if they had any substance dependence; an IQ <70; any other Axis I mental disorder; any serious cardiac, renal, or hepatic disease; had received psychotropic medications during the last 6 weeks, were pregnant or breastfeeding, or had rising liver transaminases to 3 times the upper limit of normal or higher.
• Participants received fluvoxamine 100 mg twice daily plus amantadine 100 mg/d, or fluvoxamine 100 mg twice daily plus placebo. All patients received fluvoxamine 100 mg/d for 28 days followed by 200 mg/d for the remainder of the trial.
• The primary outcome measure was difference in Y-BOCS total scores between the amantadine and placebo groups. The secondary outcome was the difference in Y-BOCS obsession and compulsion subscale scores.

Outcomes

• Patients who received amantadine augmentation experienced a significant reduction in Y-BOCS total score (P < .001) and obsession subscale score (P < .01).
• The amantadine group showed good tolerability and safety. There were no clinically significant adverse effects.

• Amantadine is an effective adjuvant to fluvoxamine for reducing OCD symptoms.

Conclusion

• Ondansetron and granisetron can be beneficial as an augmentation strategy for patients with treatment-resistant OCD.

2. Sharafkhah M, Aghakarim Alamdar M, Massoudifar A, et al. Comparing the efficacy of ondansetron and granisetron augmentation in treatment-resistant obsessive-compulsive disorder: a randomized double-blind placebo-controlled study. Int Clin Psychopharmacol. 2019;34(5):222- 233. doi:10.1097/YIC.0000000000000267

Although selective serotonin reuptake inhibitors (SSRIs) are considered a first-line treatment when teamed with CBT and antipsychotic augmentation, symptom resolution is not always achieved, and treatment resistance is a common problem. Sharafkhah et al¹¹ compared the efficacy of ondansetron and granisetron augmentation specifically for patients with treatment-resistant OCD.

Study Design

• In this 18-week, randomized, double-blind, placebo-controlled study, 135 patients with treatment-resistant OCD who were previously treated with a combination of an SSRI and an antipsychotic received augmentation with ondansetron (n = 45, 4 mg/d), granisetron (n = 45, 2 mg/d), or placebo.
• Patients were rated using Y-BOCS every 2 weeks during phase I (intervention period), which lasted 14 weeks. After completing the intervention, patients were followed for 4 more weeks during phase II (discontinuation period).
• The aim of this study was to determine the safety, efficacy, and tolerability of ondansetron vs granisetron as augmentation for patients with treatment-resistant OCD. A secondary aim was to determine the rate of relapse of OCD symptoms after discontinuing ondansetron as compared with granisetron at 4 weeks after intervention.

Outcomes

• At Week 14, the reductions in Y-BOCS scores in the ondansetron, granisetron, and placebo groups were 41.5%, 39.7%, and 15.2%, respectively (P = .001). The reduction in Y-BOCS score in the ondansetron and granisetron groups was significantly greater than placebo at all phase I visits.
• Complete response was higher in the ondansetron group compared with the granisetron group (P = .041).
• Y-BOCS scores increased in both the ondansetron and granisetron groups during the discontinuation phase, but OCD symptoms were not significantly exacerbated.

Conclusion

• Ondansetron and granisetron can be beneficial as an augmentation strategy for patients with treatment-resistant OCD.

3. Modarresi A, Sayyah M, Razooghi S, et al. Memantine augmentation improves symptoms in serotonin reuptake inhibitorrefractory obsessive-compulsive disorder: a randomized controlled trial. Pharmacopsychiatry. 2018;51(6):263-269. doi:10.1055/s-0043-120268

Increased glutamate levels in CSF, glutamatergic overactivity, and polymorphisms of genes coding the NMDA receptor have been shown to contribute to the occurrence of OCD. Memantine is a noncompetitive antagonist of the NMDA receptor. Various control trials have shown augmentation with memantine 5 mg/d to 20 mg/d significantly reduced symptom severity in patients with moderate to severe OCD. Modarresi et al¹² evaluated memantine as a treatment option for patients with severe OCD who did not respond to SRI monotherapy.

Study design

• This 12-week, double-blind, randomized, placebo-controlled trial evaluated the efficacy of memantine augmentation in 32 patients age 18 to 40 who met DSM-5 criteria for OCD, had a Y-BOCS score ≥24, and no psychiatric comorbidity. Participants had not responded to ≥3 adequate trials (minimum 3 months) of SRI therapy, 1 of which was clomipramine.
• Individuals were excluded if they were undergoing CBT; had an additional anxiety disorder, mood disorder, or current drug or alcohol use disorder, or any systemic disorder; had a history of seizures; were pregnant or breastfeeding; or had a history of memantine use.
• Participants already receiving the maximum tolerated dose of an SRI received augmentation with memantine 20 mg/d or placebo.
• The primary outcome measure was change in Y-BOCS score from baseline. The secondary outcome was the number of individuals who achieved treatment response (defined as ≥35% reduction in Y-BOCS score).

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