Clinical trial NCT00362804: Tetrabenazine for Partial Responders
Official title: Augmentation of Antipsychotic Partial Responders With Tetrabenazine
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Schizophrenia
Schizoaffective Disorder
Keywords: tetrabenazine
partial response
psychosis
schizophrenia
schizoaffective disorder
partial response to antipsychotics
Lead sponsor: Centre for Addiction and Mental Health
Sponsor class: OTHER
Collaborators: name: Stanley Medical Research Institute
First posted: 2006-08-10
Enrollment: 41
Sex: ALL
Minimum age (years): 18
Maximum age (years): 65
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief summary: Purpose of Study:

A) To improve outcome in large population of antipsychotic patients with schizophrenia or schizoaffective who are only partial responders B) To increase understanding of pharmacology and mechanisms of action underlying antipsychotic effect

Hypothesis/Objectives of the Study:

Tetrabenazine, through its pre-synaptic action, should augment the post-synaptic effects of an antipsychotic.

Background and Rationale for the study:

Preliminary evidence that other amine-depleting agents e.g., reserpine, can induce such an effect

Detailed description: Since the 1950's, antipsychotics have been used as the mainstay treatment to control symptoms of schizophrenia. However, soon after their introduction it became apparent that a substantial number of individuals show a less than optimal response to these drugs - as many as 30% of schizophrenics using conventional antipsychotics derive little benefit. Furthermore, 'atypical' generation antipsychotics such as clozapine which proves to be the most beneficial for partial responders and represents the cornerstone of treatment-resistant schizophrenia, offers a response rate as low as 30% in those showing an inadequate response. Moreover, many individuals decline clozapine as an option, or cannot tolerate it.

For these reasons, augmentation strategies play an important role in the treatment of antipsychotic partial responders. We have systematically reviewed the different augmentation options, and reached the conclusion that most such strategies are theoretically speculative and empirically unsupported.

At the same time though, we recognize that augmentation strategies are common practice in the clinical setting. With so many individuals showing only a partial response to antipsychotic treatment (typical or atypical), it has become a practical reality in efforts to offer further improvement. Often, this come in the form of adding one or even more antipsychotics, although the evidence for such an approach is less than compelling and neuroimaging from our centre has cautioned against this approach.

With a variety of other potential augmentation strategies available, we have chosen to focus on tetrabenazine (TBZ), which is currently licensed here in Canada for the management of hyperkinetic movement disorders.

The choice of TBZ as an augmentation strategy arises from several lines of investigation:

* TBZ, like reserpine, is a pre-synaptic monoamine-depleting agent or inhibitor of vesicular monoamine transporter, and hence will act to dampen abnormal dopamine release in patients already on a primary post-synaptic D2 blocking compound, as is the case (to varying degrees) with all antipsychotics currently available.
* There are anecdotal reports with reserpine, indicating that it can augment response in patients showing only a partial response to antipsychotic (atypical, as well as typical) partial responders.
* TBZ appears to have a low-affinity post-synaptic D2 effect, still well below the 80% threshold where one begins to see motor side effects.
* TBZ has inherent anti-dyskinetic properties, thereby offering an additional secondary benefit.

We are proposing to carry out a controlled double-blind trial, using TBZ off-label in patients with schizophrenia or schizoaffective disorder only partially responsive to antipsychotics. We feel that the choice of this approach is empirically sound and, in fact, offers advantages to the more common approach of adding several antipsychotics. Our decision to maintain out focus on the dopaminergic system arises from the growing body of evidence that dopamine blockade, particularly at the level of the D2 receptor, is central to antipsychotic activity, in combination with the lack of current evidence supporting the distinct advantages of incorporating other systems.

Given the limited success with augmentation strategies in schizophrenic patients to date, any evidence of efficacy and safety with this combination will add considerably to options that might be considered in the clinical setting. This same information could also prove very useful in shaping investigations related to the pharmacology of schizophrenia and development of future compounds.

Eligibility criteria: Inclusion Criteria:

* has been on an antipsychotic medication for at least 3 months and achieved the maximum dose vis à vis tolerability/side effects.
* Partial response to antipsychotic medication (CGI \> 4; BPRS \[Anchored, 18-item\] total \> 30; single item score \> 4 on 2 positive symptom items)
* has been on at least 2 previous antipsychotic trials of 4-6 weeks in duration at a dose reaching 400-600 mg chlorpromazine (or equivalent) with no clinical improvement

Exclusion Criteria:

* age \< 18 or \> 65
* previous documentation of hypersensitivity to tetrabenazine
* SCID criteria for a current depressive episode
* MAOI administration within 2 weeks of tetrabenazine treatment
* concomitant desipramine use
* diagnosis of idiopathic Parkinson's disease and/or levodopa treatment
* current unstable medical illness and current substance abuse

Primary outcomes:
measure: BPRS
timeFrame: weekly assessments
measure: CGI
timeFrame: weekly assessment
Secondary outcomes:
measure: GAF/NOISE
timeFrame: weekly
measure: SAS
timeFrame: weekly
measure: AIMS
timeFrame: weekly
measure: BAS
timeFrame: weeekly
measure: UKU (a general measure of adverse effects)
timeFrame: weekly
Other outcomes:
Locations:
city: Toronto
country: Canada
facility: Centre for Addiction and Mental Health
state: Ontario
Study officials:
affiliation: Centre for Addiction and Mental Health
name: Gary Remington, MD
role: PRINCIPAL_INVESTIGATOR
References: