Inclusion Criteria:
1. Male and female participants between 18 and 64 years of age, inclusive, at Screening Visit.
2. Participants with a documented history of CRPS of at least 6 months at Visit 1.
3. At least one sign in two of the categories of The Budapest Criteria for CRPS to support the diagnosis of CRPS.
4. Stable individual regular standard treatment regimen for CRPS pain, i.e., no change in drug and non-drug treatments for at least 4 weeks prior to Screening Visit and anticipated to remain stable throughout the study.
5. No surgery, denervation procedures or neural blockade within 1 month of Screening Visit.
6. Participants on ketamine therapy at Screening Visit must agree to discontinue use for at least 14 days prior to the Baseline Observation Period.
7. Agree to discontinue any prohibited medications within prior to 14 days of the Baseline Observation Period and for the duration of the study.
8. Average daily CRPS pain intensity score in the affected limb of ≥5 and ≤9 on an 11-point (0-10) NRS averaged over 7 days prior to Baseline Visit (Visit 1). This will be based on completion of at least 5 daily pain diary entries during the week prior to Visit 1, with no more than one 24-hour pain intensity score of zero or more than one 24-hour pain intensity score of 10.
9. Participants willing and able (e.g., mental and physical condition) to participate in all aspects of the trial, including use of medication, completion of subjective evaluations, attending scheduled clinic visits, completing telephone contacts, and compliance with protocol requirements as evidenced by providing signed written informed consent at Screening Visit.
10. For persons of reproductive potential: use of highly effective contraception (females: barrier (condom, diaphragm, sponge, cervical cap) and/or oral, implantable rod, or intrauterine device birth control; males: barrier (condom)) for at least 1 month prior to screening and agreement to use such a method during study participation and for an additional 6 weeks after the end of study intervention administration.
Exclusion Criteria:
1. Known or suspected cardiovascular disease, arrythmias, and/or respiratory issues.
2. Abnormal EKG results, abnormal blood pressure (SBP \<90 or ≥ 140; DBP \<50 or ≥ 90) and/or heart rates (\<50 or \>110).
3. Known or suspected psychotic illness or neurologic disease.
4. Known or suspected elevated intraocular and/or intracranial pressure.
5. Known or suspected renal or urologic conditions or symptoms (i.e., bladder pain syndrome, interstitial cystitis), and/or abnormal baseline urinalysis results.
6. Known or suspected hyperthyroidism.
7. Allergy, hypersensitivity, or intolerance to ketamine or any of the investigational product excipients.
8. Participants receiving opioids ≥30 mg/day morphine milligram equivalents (MME), whether as part of their individual standard treatment regimen for CRPS pain or in context with any other indication, within the last two weeks prior to Visit 1.
9. Positive urine screen for any of the following: cocaine, amphetamine, methamphetamine, PCP, opioids, THC (other than medication used for individual standard treatment of pain) at Visit 1.
10. Known or suspected acute or chronic alcoholism, delirium tremens, or toxic psychosis.
11. Meet DSM-5 criteria for current or past substance use disorder within the last 5 years for any psychoactive substances other than nicotine or caffeine.
12. Known hepatic dysfunction or serious liver disease, including presence of aspartate aminotransferase (AST) levels ≥ 2 X upper limit of normal and/or alanine aminotransferase (ALT) levels ≥ 2 X upper limit of normal and/or total bilirubin ≥ 1.5 X upper limit of normal
13. Abnormal urinalysis, urine culture or abnormal creatinine
14. Evidence of moderate or severe renal impairment (CRCL \<60 ml/min) or participants with renal failure who are on any form of dialysis.
15. Current or previous history of seizures.
16. A positive pregnancy test/confirmed pregnancy test at the screening or baseline visit.
17. If Ask Suicide-Screening Questionnaire (ASQ) is positive at Grade 2 (moderate), subject will be excluded.
18. Any other condition of the patient that in the opinion of the investigator may compromise evaluation of the trial treatment or may jeopardize participant's safety, compliance or adherence to protocol requirements.
19. Previous enrollment in this trial or participation in any other clinical trial within the past 30 days prior to enrollment.
