NAC for Treatment-Resistant OCD and Other Related Disorders
Obsessive Compulsive Disorder (OCD)
What this study involves
The registry does not currently label this study as recruiting. Ask about its status before planning a screening visit.
- Study type
- Interventional
- Phase
- Phase 4
- Age range
- 12 years - 55 years
- Sex eligible
- All sexes
- Healthy volunteers
- Accepted
- Participants
- 90 Actual
These are starting points, not an eligibility decision. The research team must review the full requirements.
About the research
This is a randomized, double-blind, placebo-controlled study investigating N-acetylcysteine (NAC) as an augmentation therapy for individuals with treatment-resistant obsessive-compulsive disorder (TR-OCD), studied within a broader cohort of treatment-resistant Obsessive-Compulsive and Related Disorders (OCRDs).
The study's primary aim is to investigate the neurobiological mechanism by which NAC improves inhibitory control deficits in TR-OCD. This is achieved by using Magnetic Resonance Spectroscopy (MRS) to measure changes in thalamic glutamatergic metabolism. A secondary aim is to assess the clinical efficacy of this augmentation strategy on symptom severity. The central hypothesis is that improvements in inhibitory control are mediated by NAC-induced changes in brain glutamate levels.
Read the full description
Please note: This study was initially designed to investigate the effects of N-acetylcysteine (NAC) across the broader spectrum of treatment-resistant Obsessive-Compulsive and Related Disorders (OCRDs), including cohorts such as Excoriation (Skin-Picking) Disorder. The overarching scientific objective was to use NAC to elucidate the neurobiological mechanisms underlying inhibitory control deficits in this difficult-to-treat population, and thereby inform the development of novel therapeutic strategies.
Upon completion of recruitment for the current analysis phase and prior to any unblinking, we finalized our analytical strategy. To ensure the primary analysis was adequately powered to yield a definitive conclusion, it was focused on the treatment-resistant OCD (TR-OCD) cohort, which comprised the substantial majority of the sample accrued to date.
Consequently, the TR-OCD cohort was designated as the primary population for the main efficacy and mechanistic analyses. Other OCRD subgroups enrolled under the same protocol were designated for planned secondary and exploratory analyses, in line with their respective sample sizes. Analyses of these subgroups, including the SPD cohort, will be conducted once sufficient data have been accrued for robust statistical testing.
This registration has been updated to accurately and transparently reflect this final, pre-specified analytical plan, ensuring the public record aligns with the study's primary, hypothesis-driven conclusions.
Who may be able to participate?
The list below is the sponsor’s full registry wording. It can include conditions, prior treatment, test results and other requirements. A match in search does not mean you qualify.
1.Inclusion Criteria for Patient:
(1) Age between 12 and 55 years. (2) A primary diagnosis of OCD according to DSM-5 criteria. (3) Excoriation (Skin-Picking) Disorder (SPD) according to DSM-5 criteria.
(4) Met criteria for treatment resistance, defined as: (a) A Y-BOCS score ≥ 16. (b) A history of inadequate response (\<25% reduction in Y-BOCS score) to at least two different serotonin reuptake inhibitors (SSRIs) at an adequate dose for at least 12 weeks each.
1.2 Inclusion Criteria for Healthy Controls:
(1) Age and sex-matched to the patient group. (2) No personal history of any psychiatric disorder.
1.3 Exclusion Criteria for All Participants: (1) Presence of any contraindications to 3T MRI scanning (e.g., metallic implants, claustrophobia). (2) Current (within the past 6 months) diagnosis of a substance use disorder. (3) Significant or unstable neurological illness (e.g., epilepsy, multiple sclerosis, brain tumor). (4) History of significant head trauma or neurosurgery.
1.4 Additional Exclusion Criteria for Patients with TR-OCD:
(1) Current or lifetime diagnosis of a primary psychotic disorder (e.g., schizophrenia), bipolar I/II disorder, or intellectual disability. (2) Any contraindication to the use of N-acetylcysteine.
Understand screeningTreatment, groups and participation
The registry may describe treatments and study duration without a complete visit calendar. Ask the study team for the exact schedule, procedures, risks, costs and alternatives. Keep your usual care plan unless your treating clinician tells you otherwise.
- Assignment
- Random assignment
- Masking
- Triple masked
N-acetylcysteine group
NAC (N-Acetylcysteine Tablets, brand name: Flumucil) has a drug specification of 600 mg per tablet. In the first week, participants took 1200mg/d (one tablet three times daily: morning, noon, and evening). Starting from the second week until the end of the 12-week study, they took 3600mg/d (three tablets twice daily: morning and evening).
Drug: N-Acetylcysteine Tablets
Placebo group
Not reported in this registry record.
Drug: Placebo Oral Tablet
Healthy Control Group
Not reported in this registry record.
N-Acetylcysteine Tablets DRUG
In addition to participants' existing medication regimens, NAC will be added.
Placebo Oral Tablet DRUG
Placebo oral tablets are identical in appearance (size, shape, color), packaging, taste, and administration schedule to the N-Acetylcysteine tablets to maintain blinding. The tablets contain inert excipients and no active pharmacological ingredients.
What researchers are measuring
Outcome measures describe what is being studied. They are not proof that a treatment works.
Primary measures
Change from Baseline in Neurometabolite Concentrations in Key Brain Regions
Time frame: Baseline, Post-treatment (Week 12)
Change from baseline to Week 12 in the concentrations of Glutamate (Glu), Glutamate+Glutamine (Glx), and Glutathione (GSH) within two pre-specified regions of interest: the thalamus and the anterior cingulate cortex (ACC). Levels are measured in both resting and functional states using Magnetic Resonance Spectroscopy (MRS).
Change from Baseline in Inhibitory Control Performance
Time frame: Baseline, Post-treatment (Week 12)
Change from baseline to Week 12 in inhibitory control performance, as measured by the error rate on a Go-Nogo task. A decrease in the error rate indicates improvement.
Secondary measures
Yale-Brown Obsessive Compulsive Scale
Time frame: Baseline, Week 4, Week 8, Week 12
Change in the total score of the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) from baseline. Scores range from 0 to 40, with higher scores indicating greater symptom severity.
Yale-Brown Obsessive Compulsive Scale modified for Neurotic Excoriation
Time frame: Baseline, Week 4, Week 8, Week 12
Proportion of participants achieving a predefined percentage reduction in the total score from baseline to post-treatment.
Review the complete result tables and limitations in the official record.
Open official results ↗Research locations (1)
The overall study status and a local site’s status can differ. Confirm that location’s availability before traveling.
1 locations
Guangdong Mental Health Center, Guangdong Provincial People's HospitalGuangDong, Guangdong, ChinaStatus unknown
Study team and timeline
- Lead sponsor
- Guangdong Provincial People's Hospital
- Study start
- Jun 22, 2022 Actual
- Primary completion
- Nov 13, 2024 Actual
- Study completion
- Apr 13, 2026 Actual
- First posted
- May 4, 2025 Actual
- Last updated
- Nov 10, 2026 Actual
Official study contacts
No central contact is listed. Check the locations and the official record.
Official study title
Altered Brain Glutamate Level and Inhibitory Control in Treatment-Resistant Obsessive-Compulsive Disorder After N-acetylcysteine (NAC) Augmentation Therapy
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Source: ClinicalTrials.gov API v2. Information is submitted by sponsors and investigators. NLM does not approve the safety or science of all listed studies. Registry disclaimer.
Retrieved: Nov 12, 2026 · Last registry update: Nov 10, 2026