Working... Menu

Does Enhanced Glutamate Transporter Function Produce Antidepressant Effects in People With Major Depression?

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT02049385
Recruitment Status : Terminated (Severe side effects & lack of target engagement)
First Posted : January 30, 2014
Results First Posted : October 13, 2017
Last Update Posted : October 13, 2017
Information provided by (Responsible Party):
National Institutes of Health Clinical Center (CC) ( National Institute of Mental Health (NIMH) )

Brief Summary:


- At least one third of individuals with major depressive disorder (MDD) remain treatment-refractory after receiving currently available antidepressants underscoring the urgent need for new antidepressant therapies. Of the novel pharmacotherapeutic strategies seeking to rapidly alleviate depressive symptoms, glutamatergic modulators have emerged as promising potential targets. The present study sought to examine the potassium (KATP) channel activator diazoxide as a possible treatment for MDD. Diazoxide increases glutamate uptake from the synaptic cleft by activating the KATP channel to chronically increase expression of the excitatory amino acid transporter (EAAT)-2 system in glial cells. Diazoxide is FDA-approved for the treatment of sulfonylurea-induced hypoglycemia, hypoglycemia due to hyperinsulinemia, and hypertension.


- To assess the ability of diazoxide, potassium channel activator, to improve overall depressive symptomatology in patients with treatment-resistant MDD currently experiencing a major depressive episode. The efficacy of a three-week course of diazoxide will be compared to three weeks of placebo. The MADRS will serve as the main outcome measure


- Adults 18 to 65 years old with MDD who are currently depressed without psychotic features.


  • Study Phase I (Day -28 to 0):

    -- Screen and taper off medications (Days -28 to -14): Prior to consenting to this study, subjects will have undergone a screening consisting of laboratory tests, psychiatric and medical history, and psychiatric and physical examinations under protocol 01-M-0254, "The Evaluation of Patients with Mood and Anxiety Disorders and Healthy Volunteers". After consenting to this study, patients will be tapered off medications. Medications allowed and not allowed are listed in Appendix 1. Patients will be reminded to report all drugs, OTC products, and other agents to the investigators so that they can screen to avoid interactions that might make participation unsafe or might confound the research results. Patients are expected to meet all inclusion and exclusion criteria before medications are tapered (which is usually 1-2 weeks long). Subjects who are not taking medications will enter the drug-free period directly. All participants must have a score of ≥20 on the MADRS at screening and baseline of Study Phase I. Subjects who do not have a score of ≥20 on the MADRS by the end of Study Phase I will be excluded and will receive standard treatment.

  • Drug-free period (Day -14 to day 0):

    -- Subjects will begin a 2-week drug-free period prior to the administration of diazoxide or placebo.

  • Study Phase II (Day 0 to 56):

    • In this study phase, subjects will be blindly randomized to receive either diazoxide 200-400 mg/day (given BID) or a placebo administered daily by mouth for three weeks. All patients except those who have a 50% or greater decrease in MADRS from baseline at the end of the first cross over point will cross over. To avoid carry-over effects between the different test sessions, there will be an interval of 14-21 days, pending response to test session 1. Subjects will then be blindly crossed over to the second experimental condition (either diazoxide or placebo) for another three weeks. All subjects who discontinue the study or who complete study phase II will then receive either clinical treatment or the opportunity to participate in another research protocol. Patients maintaining response to treatment condition 1 after two weeks will receive an additional one week washout before being crossed over to condition 2.The total duration of the study is approximately 11-13 weeks. The duration of Study Phase I including the 14-day drug-free period is approximately 4 weeks. Study phase II is 8-9 weeks long. Thus, the total duration of the study is approximately 11-13 weeks, except for those patients who were unmedicated at time of entry into the study and therefore do not need to undergo the initial tapering off medications. Subjects will be required to be hospitalized during the entire study. Passes will be permitted if the subject is clinically stable and the pass does not interfere with the study or unit procedures.

Condition or disease Intervention/treatment Phase
Depression Drug: Diazoxide Drug: Placebo Phase 1 Phase 2

Detailed Description:


To date, available pharmacological treatments for major depressive disorder (MDD) have proven to be only modestly effective during the acute phase. We have been systematically testing different glutamatergic modulators in patients with mood disorders in order to develop improved therapeutics. A recent report found that the (beta)-lactam antibiotic ceftriaxone increased glutamate uptake by increasing GLT1(EAAT2) function and had antidepressant-like effects in animal models. Using the learned helplessness model of depression we developed outbred lines, defined a new anatomy of helplessness, and determined that synaptic loss due to excess extracellular glutamate appears to be involved in the pathophysiology of helplessness; these animals show a 40% decrease in EAAT2 astrocytic transporter expression. Together, these data suggest that astrocytic glutamate reuptake systems may be central to the pathophysiology and treatment of depression, and that agents that directly increase astrocytic glutamate uptake may represent a novel class of antidepressants.

With this protocol, we propose to test a specific new mechanism that uses diazoxide to chronically increase expression of the glutamate transporter EAAT2, resulting in removal of glutamate from the synaptic cleft. Diazoxide enhances glutamate uptake in glia by activating ATP-sensitive potassium (KATP) channels. We expect that this effect will reduce excessive glutamate transmission and be associated with acute antidepressant effects. The model presented here is a clinically testable one. If successful, it may lead to the development of a group of novel pharmacological treatments for major depressive disorder.

Study Population:

24 individuals with treatment-resistant major depressive disorder.


Male and female patients diagnosed with MDD, ages 18 to 65 years, currently experiencing a major depressive episode, will be recruited for this study. The study will comprise the double-blind crossover administration of either diazoxide (200-400 mg/day given orally) or placebo. The study will assess the efficacy of three weeks of a glutamate transporter enhancer (diazoxide, 200-400 mg/day given orally) compared with placebo in improving overall depressive symptomatology in patients with treatment-resistant MDD. Other aims of the study include: 1) determining whether changes in brain neurochemicals (glutamate) correlate with antidepressant response (as measured by decreases in Montgomery-Asberg Depression Rating Scale (MADRS) total scores) in response to diazoxide in patients with treatment-resistant MDD; and 2) examining other potential biomarkers of response.

Outcome Measures:

Primary: MADRS total score. Secondary outcome measures: proportion of subjects achieving remission (MADRS score less than or equal to 10) and response (more <50% reduction from baseline in MADRS total score); change from baseline in Beck Depression Inventory (BDI), Hamilton Anxiety Rating Scale (HAM-A), Hamilton Depression Rating Scale (HAM-D), Visual Analog Scale (VAS), and the Columbia Suicide Severity Rating Scale (C-SSRS) total scores.

Layout table for study information
Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 10 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary Purpose: Treatment
Official Title: A Pathophysiological Study to Determine if Enhancing Glutamate Transporter Function Produces Antidepressant Effects in Patients With Major Depressive Disorder
Study Start Date : January 3, 2014
Actual Primary Completion Date : July 21, 2016
Actual Study Completion Date : July 21, 2016

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Antidepressants
Drug Information available for: Diazoxide

Arm Intervention/treatment
Experimental: Diazoxide
Subjects received 200-400 mg daily of diazoxide orally for three weeks; the dose was, adjusted depending on side effects and response.
Drug: Diazoxide
A nondiuretic vasodilator thiazide-related agent

Experimental: Placebo
Subjects received a matched placebo for three weeks
Drug: Placebo

Primary Outcome Measures :
  1. MADRS Change at Day 7 [ Time Frame: 7 days ]
    Change in Montgomery Asberg Depression Rating Scale (MADRS) from baseline to 7 days post-treatment. The range of values is from 0 - 60, with a higher score indicating increased depressive symptoms. A score of 7-19 indicates mild depression; 20-34 indicates moderate depression; >34 indicates severe depression.

Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.

Layout table for eligibility information
Ages Eligible for Study:   18 Years to 65 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

    • 18 to 65 years of age.
    • Women of child bearing potential must have a negative serum pregnancy test and confirmed (by the investigator) use of two effective methods of contraception (see below).
    • Each subject must be capable of understanding all required tests and examinations and must sign an informed consent document.
    • Subjects must fulfill DSM-IV criteria for MDD, single episode or recurrent without psychotic features, based on clinical assessment and confirmed by a structured diagnostic interview (SCID-P). Subjects must be experiencing a current major depressive episode of at least four weeks duration.
    • Subjects must have an initial score of at least 20 on the MADRS at screening and at baseline of study Phase I.
    • Subjects must have a current or past history of lack of response to two adequate antidepressant trials (may be from the same chemical class) operationally defined using the modified-Antidepressant Treatment History Form (ATHF).


  • Current psychotic features or a current or past diagnosis of schizophrenia or any other psychotic disorder as defined in the DSM-IV.
  • Subjects with a history of DSM-IV drug or alcohol dependency or abuse (except for caffeine or nicotine dependence) within the preceding three months.
  • Head injury that results in loss of consciousness exceeding five minutes (for the imaging component of the study).
  • Subjects with a DSM IV Axis II diagnosis of borderline or antisocial personality disorder.
  • Pregnant or nursing women or women of child bearing potential not using two medically accepted means of contraception (including oral, injectable, or implant birth control, condoms, a diaphragm with spermicide; intrauterine devices (IUD); tubal ligation; abstinence; or partner with vasectomy).
  • Serious, unstable medical illnesses including hepatic, renal, gastroenterologic, respiratory, cardiovascular (including ischemic heart disease), endocrinologic, neurologic, immunologic, or hematologic disease.
  • Subjects with hyperthyroidism or clinical hypothyroidism.
  • Subjects with one or more seizures without a clear and resolved etiology.
  • Clinically significant abnormal laboratory tests (including blood glucose).
  • Diabetes
  • Fasting plasma glucose concentration >120 mg/dl
  • Upright diastolic blood pressure <60mmHg on three occasions 30 minutes apart (based on scheduled research measurements).
  • Treatment with a reversible MAOI within four weeks of study Phase II.
  • Treatment with fluoxetine within five weeks of study Phase II.
  • Treatment with any other disallowed concomitant medication 14 days before randomization.
  • Treatment with clozapine or ECT within one month of randomization.
  • Lifetime history of deep brain stimulation.
  • Subjects who, in the investigator's judgment, pose a current serious suicidal or homicidal risk.
  • Positive HIV test
  • Contraindications to MRI (metal in body, claustrophobia, etc)

No structured psychotherapy will be permitted during the study.

Definition of treatment-resistance

All subjects are required to have previously failed to respond to two adequate antidepressant trials (may be from the same chemical class). Adequacy of antidepressant trials will be determined via the clinician administered modified ATHF.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT02049385

Layout table for location information
United States, Maryland
National Institutes of Health Clinical Center, 9000 Rockville Pike
Bethesda, Maryland, United States, 20892
Sponsors and Collaborators
National Institute of Mental Health (NIMH)
Layout table for investigator information
Principal Investigator: Carlos A Zarate, M.D. National Institute of Mental Health (NIMH)

Layout table for additonal information
Responsible Party: National Institute of Mental Health (NIMH) Identifier: NCT02049385     History of Changes
Other Study ID Numbers: 140041
14-M-0041 ( Other Identifier: The National Institutes of Health )
First Posted: January 30, 2014    Key Record Dates
Results First Posted: October 13, 2017
Last Update Posted: October 13, 2017
Last Verified: July 2017

Layout table for additional information
Studies a U.S. FDA-regulated Drug Product: Yes
Studies a U.S. FDA-regulated Device Product: No

Keywords provided by National Institutes of Health Clinical Center (CC) ( National Institute of Mental Health (NIMH) ):

Additional relevant MeSH terms:
Layout table for MeSH terms
Depressive Disorder
Behavioral Symptoms
Mood Disorders
Mental Disorders
Antidepressive Agents
Psychotropic Drugs
Antihypertensive Agents
Vasodilator Agents