Silexan in the Treatment Of Posttraumatic Stress Disorder Trial

NCT06412757 | Recruiting Phase 3 DMC

• 2 other identifiers: 29307HT9425-23-1-0885
• Study Type: interventional
• Target: 278
• Locations: 1 country
• Sites: 4

Brief Summary

Posttraumatic stress disorder (PTSD) is a common and debilitating mental illness. Current treatments for PTSD include psychotherapy and antidepressant medications. Many patients are unable to tolerate psychotherapy for PTSD and drop out of it. In addition, its effectiveness is limited. Up to 50 percent of patients who receive psychotherapy do not benefit from it. Antidepressant medications have only small benefits in PTSD. They also have unpleasant side effects that can make patients unwilling to take them. There is an urgent need to develop new treatments for PTSD that work and are well-tolerated. Silexan has the potential to provide an important alternative treatment for PTSD. Silexan is derived from lavender oil. It is taken orally in the form of capsules. It is currently available over-the-counter in 14 countries, including Australia and the United States. Previous research has shown that it is an effective treatment for anxiety disorders, including Generalized Anxiety Disorder. It is also well-tolerated by patients. The only side effects that have been identified so far are mild gastrointestinal symptoms (including burping and breath odour) and these are uncommon. The results of a small pilot study suggest that Silexan may also be effective and well-tolerated in PTSD. The STOP trial is a clinical trial that aims to investigate whether adding Silexan to treatment-as-usual improves PTSD symptoms in adults with PTSD. The trial will recruit 278 participants. Participants will be randomly assigned to take Silexan or a placebo (look-alike dummy pills) daily in addition to their usual medications for 12 weeks. The severity of their PTSD symptoms will be assessed prior to and at the end of this 12-week period. The STOP trial has the potential to obtain definitive evidence regarding whether Silexan helps treat symptoms of PTSD. If Silexan is found to be an effective treatment for PTSD, the pool of patients who could potentially benefit from this treatment includes any adults with PTSD. Silexan is already available over-the-counter at a relatively low cost so there will be few barriers to accessing this treatment.

Conditions

Post Traumatic Stress Disorder

Keywords

posttraumatic stress disorder; adjunctive treatment; Silexan; phytoceutical; pharmacotherapy; randomized controlled trial

Outcome Measures

Primary Outcomes (1)

• Clinician-Administered PTSD Scale for DSM-5 (CAPS-5)

  The Primary Outcome Measure will be the between-group difference in the change from baseline to week 12 in the total symptom severity score on the CAPS-5. The CAPS-5 has good internal consistency, inter-rater reliability, test-retest reliability and convergent validity in measuring PTSD symptom severity, and is regarded as the gold-standard for measuring PTSD symptoms in research settings. The CAPS-5 will be used to query the presence of PTSD symptoms across the two weeks prior to each CAPS-5 assessment. We will also compare between-group differences in remission rates of PTSD, as determined by the CAPS-5.

  At baseline and at week 12 of the study period

Secondary Outcomes (19)

• Hamilton Anxiety Rating Scale (HAM-A)

  At baseline, at week 12 and at week 16 of the study period

• Generalized Anxiety Disorder-7 (GAD-7)

  At baseline, at week 12 and at week 16 of the study period

• Generalized Anxiety Disorder-7 (GAD-7)

  At baseline, week 4, week 8 and week 12 of the study period

• Beck Depression Inventory-II (BDI-II)

  At baseline, at week 12 and at week 16 of the study period

• Patient Health Questionnaire-9 (PHQ-9)

  At baseline, at week 12 and at week 16 of the study period

Other Outcomes (1)

• Mediators of response to Silexan

  Baseline

Study Arms (2)

Silexan 160 mg

EXPERIMENTAL

Participants in the Silexan arm will take Silexan 160 mg daily in the morning for 12 weeks in addition to their usual prescribed psychoactive medications. Participants will be followed up at 2, 4, 6, 8 and 12 weeks of the intervention period, as well as at 4 weeks post-treatment (off-treatment follow-up period).

Drug: Silexan

Placebo

PLACEBO COMPARATOR

Participants in this arm will take two placebo capsules daily in the morning for 12 weeks in addition to their usual medications. Participants will be followed up at 2, 4, 6, 8 and 12 weeks of the intervention period, as well as at 4 weeks post-treatment (off-treatment follow-up period).

Other: Placebo

Interventions

Silexan DRUG

Participants in the Silexan arm will take two over-encapsulated capsules, each containing 80 mg Silexan, daily orally in the morning in addition to their usual medications. No modifications of allocated interventions will be made for any trial participants; if appropriate (i.e following the emergence of adverse events) participants will be withdrawn from the intervention.

Silexan 160 mg

Placebo OTHER

Participants in the placebo arm will take two capsules containing an inert placebo daily orally in the morning in addition to their usual medications. The placebo capsules will contain a sub-therapeutic amount of lavender oil to mimic the odor of the experimental drug (Silexan).

Placebo

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Aged 18 years or over.
• Fluent in English.
• Meet DSM-5 criteria for PTSD, irrespective of occupation (e.g. first responder, police officer, ex-military or civilian), determined using the Mini International Neuropsychiatric Interview 7.0.2.
• Have a score on the PTSD Checklist for DSM-5 (PCL-5) equal to or over 33.

You may not qualify if:

• Are currently serving in the Australian Defence Force
• Lifetime history of a psychotic or bipolar disorder, or dissociative identity disorder.
• Moderate or severe alcohol or other substance use disorder within 3 months of screening.
• Active suicidal or homicidal ideation.
• Borderline Personality Disorder (BPD).
• Acute or unstable medical illness or other significant medical condition, that would make participation in the trial unsafe or inappropriate.
• Pregnancy, lactation or unwillingness to use an acceptable method of contraception (required for both males and females who are of reproductive potential and sexually active with partners of the opposite sex) through the duration of participants' involvement in the study up to and including week 16. Participants will also be advised not to donate eggs or sperm during the study period.
• Commencement of a trauma-focussed psychotherapy (including Prolonged Exposure, Cognitive Processing Therapy and Eye Movement Desensitisation and Reprocessing) within 3 months of screening.
• Commencement or change in dose of psychoactive medications within 4 weeks of screening.
• Participants will be asked not to initiate psychotherapy or change the dose of psychoactive medications during the course of the study except in clinically urgent circumstances; if this becomes necessary, a decision will be made on a case-by-case basis with regard to retaining the participant or terminating their participation.
• Severe acquired brain injury.
• Individual is not eligible for public mental health services due to their visa status in Australia or for any other reason.
• Any other condition that in the opinion of the research team is likely to make completion of the trial requirements infeasible.
• Inability to understand or speak English to the extent necessary to give informed consent and complete the trial (researcher or clinician-determined).

Sponsors & Collaborators

• Ramsay Clinic Albert Road: collaborator
• Deakin University: lead
• University of Melbourne: collaborator

Study Sites (4)

University of Melbourne

Carlton, Victoria, 5053, Australia

RECRUITING

Deakin University

Geelong, Victoria, 3220, Australia

RECRUITING

Austin Health

Heidelberg, Victoria, 3084, Australia

RECRUITING

Ramsay Clinic Albert Road

Melbourne, Victoria, 3004, Australia

RECRUITING

MeSH Terms

Conditions

Stress Disorders, Post-Traumatic

Interventions

lavender oil

Condition Hierarchy (Ancestors)

Stress Disorders, Traumatic; Trauma and Stressor Related Disorders; Mental Disorders

Study Officials

• Michael Berk, PhD

  Deakin University

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Greg Roebuck, MD

CONTACT

+61 3 9035 4749; greg.roebuck@unimelb.edu.au

Georgia Parkin, PhD

CONTACT

+61 3 9035 3417; georgia.parkin@unimelb.edu.au

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: All study team members will be blinded to allocation. Blinding will be maintained by ensuring that the packaging, appearance and color of the Silexan (treatment) and placebo capsules are identical. Placebo capsules will also include a sub-therapeutic amount of lavender oil to match the odour of the Silexan capsules. In addition, blinding will be maintained by identifying participants using anonymous participant identifier numbers; an independent statistician will coordinate randomization and an independent pharmacist will store and provide blinded batches to study team members for dispensing.
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator

Model Details: The trial is a phase 3, 12-week, parallel-arm, randomized, placebo-controlled, double-blind trial. Participants will be randomly allocated to receive either (a) Silexan 160 mg or (b) an identical appearing inert placebo, daily for 12 weeks in addition to their usual prescribed medications.

Study Record Dates

• First Submitted: May 9, 2024
• First Posted: May 14, 2024
• Study Start: August 26, 2024
• Primary Completion (Estimated): May 1, 2027
• Study Completion (Estimated): June 1, 2027
• Last Updated: December 18, 2025

Record last verified: 2025-12

Data Sharing

• IPD Sharing: Will share
• Shared Documents: ICF
• Time Frame: A copy of the blank, ethics-approved consent form will be posted on clinicaltrials.gov, after the trial is closed to recruitment and no later than 60 days after the last study visit, in accordance with United States federal requirements described in Code of Federal Regulations, Title 32, Part 219 (32 CFR 219).

Locations

AU (4)