Does Enhanced Glutamate Transporter Function Produce Antidepressant Effects in People With Major Depression?
Status:
Terminated
Trial end date:
2016-07-21
Target enrollment:
Participant gender:
Summary
Background:
- 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.
Objectives:
- 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
Eligibility:
- Adults 18 to 65 years old with MDD who are currently depressed without psychotic features.
Design:
- 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.