Intervention: Naltrexone
Trial phase: Phase 2
ATC code: A08AA62 | N02AA56 | N07BB04
SMILES: [H][C@@]12Oc3c(O)ccc4c3[C@@]13CCN(CC1CC1)[C@]([H])(C4)[C@]3(O)CCC2=O
Sex: All
Age groups: Adult | Older Adult
Healthy volunteers: No
Participants at risk: 6
Group description: In this arm, patients will receive active naltrexone for 3 weeks. 1 mg of naltrexone will be given twice daily to all patients assigned to active drug.
Eligibility criteria:
Inclusion Criteria:

Age 18-65.
Written informed consent.
Meet Diagnostic and Statistical Manual (DSM-IV) criteria by Structured Clinical Interview for DSM-IV (SCID-I/P) for Major Depressive Disorder (MDD), current.
Quick Inventory of Depressive Symptomatology - Self-Rated (QIDS-SR) score of at least 12 at both screen and baseline visits.

Received treatment with either an Selective serotonin re-uptake inhibitors (SSRI) in combination with a dopaminergic agent, or with an antidepressant with a dopaminergic mechanism of action in adequate doses, achieved remission per American College of Neuropsychopharmacology (ACNP) Task Force guidelines for ≥3 months, currently in relapse or recurrence without dose change for at least the past 4 weeks, based on meeting DSM-IV criteria for MDD.

Dopaminergic agents here include classical stimulants from the amphetamine or methylphenidate families; dopamine agonists (e.g. pramipexole); or dopamine active antidepressants like bupropion.
Additionally, low dose (< 2.5 mg) Abilify, a D2 partial agonist, is believed to exert pro-dopaminergic effects and will therefore be included as a dopamine agent.
Sertraline, although classified as an SSRI, has dopamine reuptake inhibiting properties believed to be relevant at higher doses (> 150 mg of sertraline), and will also therefore be considered a dopaminergic antidepressant at dose range above.
Based on the finding that the norepinephrine transporter is the reuptake inhibitor for dopamine in the prefrontal cortex and the robust sustained clinical response of a patient on duloxetine and low dose naltrexone, we include duloxetine, traditionally classed as an SNRI, among the dopamine acting antidepressants.)
During the baseline visit, patients must be on a stable dose of antidepressant regimen for the past 4 weeks.

Exclusion Criteria:

Pregnant women or women of child bearing potential who are not using a medically accepted means of contraception (to include oral contraceptive or implant, condom, diaphragm, spermicide, intrauterine device, tubal ligation, or partner with vasectomy).
Patients who no longer meet DSM-IV criteria for MDD during the baseline visit.
Patients who demonstrate a greater than 25% decrease in depressive symptoms as reflected by the QIDS-SR total score - screen to baseline.
Serious suicide or homicide risk, as assessed by evaluating clinician.
Unstable medical illness including cardiovascular, hepatic, renal, respiratory, endocrine, neurological, or hematological disease.
Substance use disorders active within the last six months, any bipolar disorder (current or past), any psychotic disorder (current or past).
History of a seizure disorder or clinical evidence of untreated hypothyroidism.
Patients requiring excluded medications (including but not limited to chronic or episodic use of anorexiants, episodic hormones, episodic benzodiazepines, episodic insulin, episodic and other episodic psychotropic medications).
Psychotic features in the current episode or a history of psychotic features, as assessed by SCID.
History of naltrexone intolerance at any dose.
Patients with a history of antidepressant-induced hypomania.
Inadequate exposure time or dose of current SSRI or Serotonin-norepinephrine reuptake inhibitor (SNRI); failure to comply with at least 80% of doses.