• Are able to provide proof of veteran status.

• Are fluent in speaking and reading English.

• At Baseline, meet criteria for Alcohol Use Disorder as measured by the SCID-5.

• Able to safely abstain from alcohol for at least 48 hours without requiring medical detox.

• At Baseline meet DSM-5 criteria for current PTSD with a symptom duration of at least 6 months.

• At Baseline, have a PCL-5 score of 33 or greater.

• At Baseline, have a confirmed PTSD diagnosis per the CAPS-5 and a Total Severity Score of 28 or greater.

• Are able to swallow pills.

• Agree to have study visits recorded, including Experimental Sessions, assessments, and non-drug therapy sessions.

⁃ Able to provide a contact (relative, spouse, close friend, or other support person) who is willing and able to be reached by the investigators in the event of a participant becoming unwell or unreachable.

⁃ Able to identify appropriate support person(s) to stay with the participant on the evenings of the Experimental Sessions, see Section Support Person.

⁃ Weight

⁃ Body weight of at least 45 kilograms (kg). Participants with a body weight of 45 to 48 kg must also have a body mass index (BMI) within the range of 18 to 30 kg/m2.

⁃ Sex and Contraceptive/ Barrier Requirements

⁃ For participants assigned female sex at birth:

∙ A participant is eligible to participate if not pregnant, not planning to become pregnant, or is not breastfeeding and one of the following conditions applies

‣ Is not able to become pregnant

‣ Is a person able to be pregnant (PABP) and using a contraceptive method that is highly effective, with a failure rate of \<1%. The investigator will evaluate the potential for contraceptive method failure (e.g., noncompliance, recently initiated) in relationship to the first does of study intervention. A PABP must have a highly sensitive negative urine pregnancy test at study entry and prior to each Experimental Session, see Schedule of Activities. The investigator is responsible for review of medical history, menstrual history, and recent sexual activity to decrease the risk for inclusion of a participant with an early undetected pregnancy.

⁃ Informed Consent

⁃ Capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the ICF and in this protocol.

⁃ Other Inclusions

⁃ Agree to inform the investigators within 48 hours of any medical conditions and procedures.

⁃ May have asymptomatic Hepatitis C virus (HCV) that has previously undergone evaluation and treatment as needed.

⁃ Participants must have a plan, agreed upon by investigator, therapy team, and study clinician, to reduce use of substances and to manage symptoms without self-medicating. Enrollment will require that, in the judgment of the investigator, therapy team, and study physician, the plan for decreasing substance use is realistic and has a good chance of succeeding to prevent substance use from impacting the safety or efficacy of the investigational treatment.

⁃ May have a history of or current Diabetes Mellitus (Type 2) if additional screening measures rule out underlying cardiovascular disease, if the condition is judged to be stable on effective management, and with approval by the study clinician.

⁃ May have hypothyroidism if taking adequate and stable thyroid replacement medication.

⁃ May have a history of, or current, glaucoma if approval for study participation is received from an ophthalmologist.