Condition category
Mental and Behavioural Disorders
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims:
Depression is common and most depressed patients are treated by their general practitioner (GP). Antidepressants are very widely prescribed, but a substantial proportion of those who take them do not get better. There is very little evidence to guide GPs when this happens, and most are unsure what to do when their patients do not respond to the medication. Many patients remain in a depressed state for long periods of time, despite taking antidepressant treatment. We are looking for other ways to help those whose depression does not respond to initial treatment, and we think that it might be useful to use combinations of antidepressant drugs. Combination treatments are used in many areas of medicine, including other common conditions such as hypertension and diabetes.
Most of the antidepressants prescribed in the UK as first line treatment are Selective Serotinin Reuptake Inhibitors (SSRIs) like Fluoxetine (Prozac). However, there is another well-established antidepressant called Mirtazapine, that works in a different way from SSRIs and the related noradrenaline reuptake inhibitors (SNRIs). We propose a large study in general practice, where most depression is treated, to examine the effectiveness and cost-effectiveness of the combination of mirtazapine and an SSRI or SNRI.

Who can participate?
Patients from primary care who are depressed and have taken an SSRI or SNRI antidepressant for at least six weeks without substantial benefit. They must be aged between 18 and 75 and must not be suffering from a psychotic disorder or be dependent on drugs and alcohol. They must not be pregnant.

What does the study involve?
Participants who agree will be randomly allocated to receive either mirtazapine treatment or a dummy drug (placebo) that appears identical. Neither the participant, GP, or study investigator will know whether the participant is taking mirtazapine or placebo. They will continue to take their SSRI antidepressant and be treated by their GP in the usual way.

What are the possible benefits and risks of participating?
If it proves effective, this combination has the potential to rapidly make a difference for people with depression that does not respond to usual first line antidepressant treatment. Mirtazapine has been licensed in the UK for the treatment of depression since 1994, and its adverse effect profile is well known. Its principal effects are increase in appetite, weight gain and drowsiness. Mirtazapine continues to be used in psychiatric settings in combination with other antidepressants without the reporting to date of any unexpected or new adverse events.

Where is the study run from?
Bristol University. The other participating centres are the Universities of Exeter, Manchester and York.

When is study starting and how long is it expected to run for?
The study begins on 01 January 2013 and will run for 42 months

Who is funding the study?
NIHR Health Technology Assessment Programme (HTA)

Who is the main contact?
Dr David Kessler

Trial website

Contact information



Primary contact

Dr David Kessler


Contact details

University of Bristol
School of Social & Community Medicine
Oakfield House
Oakfield Grove
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number

HTA 11/129/76

Study information

Scientific title

A double blind placebo-controlled randomised trial of the addition of mirtazapine for patients with depression in primary care who have not responded to at least 6 weeks of treatment with a selective serotonin reuptake inhibitor or serotonin and noradrenaline reuptake inhibitor.



Study hypothesis

That the addition of mirtazapine will improve outcome in depressed patients from primary care who have not responded to an SSRI antidepressant after at least 6 weeks of treatment

Ethics approval

Not provided at time of registration

Study design

A two parallel group multi-centre pragmatic placebo-controlled randomised trial with allocation
at the level of the individual

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet




The addition of Mirtazapine to SSRI antidepressants

Intervention type



Not Applicable

Drug names


Primary outcome measures

Change in Beck Depression Inventory score at 12 weeks measured as a continuous variable

Secondary outcome measures

1. 50% improvement in BDI score (remission)
2. A measure of anxiety (GAD7)
3. Quality of life (EQ-5D-5L)
4. Health care utilisation

Overall trial start date


Overall trial end date


Reason abandoned


Participant inclusion criteria

1. Aged 18-75 years
2. Currently taking any of the following SSRI or SNRI antidepressants, for at least 6 weeks at recommended (BNF) doses:
2.1. Fluoxetine
2.2. Sertraline
2.3. Citalopram
2.4. Escitalopram
2.5. Fluvoxamine
2.6. Paroxetine
2.7. Duloxetine
2.8. Venlafaxine and who have done so for at least 6 weeks at
3. Patients who score 14 or more on the Beck Depression Inventory (BDI)
4. Patients who have adhered to their medication and meet ICD-10 criteria for depression (assessed using the Computerised Interview Schedule – Revised version (CIS-R))

Participant type


Age group




Target number of participants


Participant exclusion criteria

GPs will be asked to exclude patients who have bipolar disorder, psychosis or alcohol/substance abuse/dependence or who are pregnant. In addition, we will exclude patients who: are not able to complete the study questionnaires or have a past history of an adverse reaction to mirtazapine.

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

University of Bristol
United Kingdom

Sponsor information


University of Bristol (UK)

Sponsor details

c/o Dr Birgit Whitman
Research Governance and Compliance Manager
Research and Enterprise Development
Senate House
Tyndall Avenue
United Kingdom

Sponsor type




Funder type


Funder name

NIHR Health Technology Assessment Programme - HTA (UK) ref: 11/129/76

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Results - basic reporting

Publication summary

2016 protocol in:

Publication citations

Additional files

Editorial Notes

05/02/2016: Publication reference added.