PCORI Comparative Effectiveness Study-Esketamine (Spravato) vs. Ketamine-Equivalence Study

Inclusion Criteria: * Provision of signed and dated informed consent form * Stated willingness to comply with all study procedures and availability for the duration of the study * Adults ages 18 or older * Diagnosis of major depressive disorder that is refractory to two or more antidepressant trials * Moderate or severe depression based on an initial MADRS score ≥ 25 * Judged appropriate for ketamine or esketamine by clinician, independent of potential study participation * A female participant must be: a. Not of childbearing potential\*, OR b. Of childbearing potential and practicing a highly effective method of contraception (failure rate of \<1% per year when used consistently and correctly) and agrees to remain on a highly effective method while receiving study intervention and until 1 week after last dose - the end of relevant systemic exposure. The investigator will evaluate the potential for contraceptive method failure (e.g., noncompliance, recently initiated) in relationship to the first dose of drug. Acceptable methods of contraception are: i. combined (estrogen and progestogen containing) hormonal or progestogen-only hormonal contraception associated with inhibition of ovulation (oral, transdermal, or intravaginal) ii. intrauterine device (IUD) iii. intrauterine hormone-releasing system (IUS) iv. bilateral tubal occlusion/ligation v. male partner with a bilateral vasectomy with documented aspermia or a bilateral orchiectomy vi. male or female condom with spermi…