Inclusion Criteria:
1. able to speak/read English,
2. not seeking treatment for drug use at the time of the study,
3. female or male between the ages of 18 and 55 years,
4. recent methamphetamine use verified by methamphetamine positive urine, as well as fulfillment of DSM-5 diagnostic criteria for MUD,
5. judged to be medically and psychiatrically healthy by study physicians other than the diagnosis for MUD (and OUD for the co-morbid MUD and OUD group, see below) at the time of screening,
6. ECG, read by a cardiologist, within normal limits,
7. females using an effective form of birth control and not pregnant or breastfeeding,
8. no known contraindications (e.g., hepatic disease \[save for asymptomatic HCV status as cleared by study physician\]) or allergies to troriluzole. Individuals in the MUD and OUD group must also report recent opioid use, verified by opioid positive urine, as well as fulfillment of DSM-5 diagnostic criteria for OUD with physiologic dependence (determined to not be physically dependent if a participant arrives with a urine sample for drug screening that is negative for a short-acting opioid and does not have a score of 5 or greater on the clinical opioid withdrawal scale \[COWS\]).
Exclusion Criteria:
1. unable to speak/read English,
2. seeking treatment for drug use,
3. under 18 years or over 55 years,
4. no recent methamphetamine use as indicated by methamphetamine negative urine and no DSM-5 diagnosis of MUD,
5. judged to be medically and psychiatrically unhealthy by study physicians at the time of screening,
6. ECG, read by a cardiologist, outside normal limits,
7. females not using an effective form of birth control or pregnant or breastfeeding,
8. blood pressure readings indicative of hypertension (i.e., blood pressure \> 140/90 mmHg) on 2 consecutive screening visits,
9. BMI \< 18 or \> 30; weight \< 50 kg,
10. taking any medications prescribed by a physician for a chronic condition,
11. any laboratory chemistry values (e.g., LFTs) \> 3 times normal at screening or during admission,
12. history of serious physical disease or diagnosis of any disorder (e.g., current hepatic disease \[save for asymptomatic HCV status; as noted above\], histories of seizure, diabetes, asthma or CNS tumors) or current or past histories of psychiatric disorder, including current or recent suicidal ideation that would limit compliance in the study, other than MUD or tobacco use disorder (and OUD for the co-morbid MUD/OUD group only) that in the opinion of the study physicians would interfere with participation and
13. contraindications (e.g., hepatic disease) or allergies to troriluzole.
