Mirtazapine for the Treatment of Methamphetamine Use in Opioid Use Disorder Patients Receiving Medication Assisted Treatment

Inclusion Criteria:

• Enrollment at medication for opioid use disorder (MOUD) treatment at Oregon Recovery & Treatment Center/clinics in Spokane, WA.

• Verification of a DSM-5104 diagnosis of an methamphetamine (MA) use disorder (i.e.mild, moderate, or severe),

• Aged 18+ years,

• Ability to provide written informed consent,

• Demonstration of 78% adherence rate during the induction period and

• Provision of at least one MA positive urinalysis at baseline or during induction.

• Baseline complete blood cell count (CBC), total protein, albumin, glucose, alkalinephosphatase, creatinine, BUN, and electrolytes without clinically significantabnormalities as determined by clinician in conjunction with symptoms, physicalexam, and medical history.

• No current acute illness requiring prolonged medical care.

• No serious chronic illnesses that are likely to progress clinically during trialparticipation.

• Vital signs are within the normal ranges (i.e., Blood pressure: 90/60 mm Hg to 120/80 mm Hg; breathing: 12-18 breaths per minute; pulse: 60-100 beats per minute;temperature: 97.8 - 99.1 degrees Fahrenheit.

Exclusion Criteria:

• Inability to demonstrate competency to provide informed consent because of cognitiveor psychiatric disorders or limited English proficiency,

• Prior diagnosis of dementia,

• Medically or psychiatrically unsafe to participate as determined by Dr. Layton (Medical Director),

• Documented suicide attempt in the past 30 days and/or serious suicide intention orplan as assessed by the Structured Clinical Interview for DSM-5 (SCID-5; clinicaltrials version)105

• Suicide attempt in the last 2 years

• Moderate or severe liver disease (AST, ALT, and total bilirubin >= 5 times upperlimit of normal),

• Impaired renal function (estimated GFR <40 ml/min),

• Current severe cocaine, amphetamine, or alcohol use disorder as defined by DSM-5criteria which Drs Layton and McPherson deem their participation as unsafe.

• History of bipolar disorder or psychotic disorder, as determined by StructuredClinical Interview for DSM Disorders (SCID,

• Currently taking 1) any type of opioid use disorder medication other than methadoneor buprenorphine/naloxone, or 2) phenytoin, carbamazepine, or another inducer ofhepatic metabolism (such as rifampicin) and CYP enzyme inhibitor cimetidine.

• Taking an anti-depressant medication within the past 30 days, including mirtazapineor a monoamine oxidase inhibitor,

• Prescribed MZP in the least year, or

• History of violent criminal behavior or being on parole,.

• Currently pregnant or intending to become pregnant,.

• Final determination of eligibility will be made by Dr. Layton in consultation withthe PI.