A Two-Part, Double Blinded, Placebo Controlled, Crossover Repeated Stepped Infusion Dose Study of Respiratory Pharmacodynamics of GAL- 021 and Opioids (Protocol - GAL-021-104).

1. Subjects must be willing to give written informed consent for the trial and able to ad-here to dose and visit schedules.
2. The subject is male >18 to <=45 years of age.
3. Subject must weigh >=60 to <=90 kg .
4. Subjects must have Body Mass Index [weight/height2 (kg/m2)] between 18 to 30 kg/m2.
5. Have no clinical or electrocardiographic signs of ischemic heart disease as determined by the Investigator with normal cardiac intervals appropriate for their gender. The Screening 12 lead ECG conduction intervals must be within gender specific normal range (e.g., QTcF males <= 430 msec, PR interval <= 220 msec). ECGs are to be judged by the investigator or subinvestigator as per standardized procedures.
6. Subjects* clinical laboratory tests (CBC, blood chemistry, coagulation and urinalysis) must be within normal limits or clinically acceptable to the investigator and within an allowed expanded range supplied by sponsor (Appendix 2). However, subject*s liver function test results (i.e., AST, ALT) must not be elevated above the normal limits at Screening and on Day -1. No rescreening of liver function tests will be allowed.
7. Vital sign measurements must be within the following ranges: (Individuals with values outside (or indicate lower or higher) of these ranges may be enrolled if clinically acceptable to the investigator and sponsor.
a. body temperature, between 35.5 oC and 37.5 oC
b. systolic blood pressure, 90 to 150 mm Hg
c. diastolic blood pressure, 40 to 95 mm Hg
d. pulse rate, 40 to 100 bpm
8. Non-vasectomized men must agree to use a condom with spermicide (when marketed in the country), double-barrier contraception or abstain from sexual intercourse, during the trial and for 3 months after stopping the medication.
9. Subjects must be free of any clinically significant disease that would interfere with the study evaluations.
Subjects presenting out of range values of lab/ECG/vital signs compatible with normal variation of the normal healthy subject can be included in the study at the inves-tigator*s discretion and sponsor written approval.

1. Current diagnosis of psychiatric disease requiring daily medication, including controlled or uncontrolled schizophrenia, current or recently treated depressive disorders, or Columbia-Suicide Severity Rating Scale (C-SSRS) indicative of suicidal ideation or behavior at screening.
2. Past history of the anxiety disorder including panic attack, depression, obsessive compulsive disorder, phobias restricting normal daily function, social anxiety, and paranoia.
3. History of alcohol abuse (more than an average of 2-drinks per day) within the past 2 years.
4. History of smoking within the past year.
5. Failure of the drug of abuse tests at screening or check-in.
6. Positive for HIV, or Hepatitis B or C at screening.
7. Blood donation or blood loss within 60 days of screening or plasma donation within 7 days of screening.
8. Subjects with a history of bleeding disorders or coagulopathies.
9. History of dyspnea, asthma, tuberculosis, chronic obstructive pulmonary disease, sleep apnea or any other ventilatory / lung disease.
10. Treatment with another investigational drug within 3 months prior to screening or having participated in more than four investigational drug studies within 1 year prior to screening.
11. Inability to perform acceptable, quality spirometry, and FEV1 <80% of predicted for age, sex and height according to ECCS criteria.
12. History of any abuse of or sensitivity (allergies, gastrointestinal adverse effects ) to opioids.
13. History of motion sickness.
14. Subjects with excessive facial hair preventing sealing of the occlusive face mask.
15. Subjects who, in the opinion of the investigator, will not be able to participate optimally in the study.
16. Any surgical or medical condition which might significantly alter the distribution, me-tabolism or excretion of any drug. The investigator should be guided by evidence of any of the following, and be discussed with the sponsor prior to enrollment into the trial:
a. history of pancreatic injury or pancreatitis;
b. history or presence of liver disease or liver injury;
c. history or presence of impaired renal function as indicated by clinically significant elevation in creatinine, BUN/urea, urinary albumin, or clinically significant urinary cellular constituents; or
d. history of urinary obstruction or difficulty in voiding.
17. Subject who has a history of any infectious disease within 4 weeks prior to drug ad-ministration that in the opinion of the investigator, affects the subject*s ability to participate in the trial.
18. Subjects who are part of the study staff personnel or family members of the study staff personnel.
19. Subjects who have demonstrated allergic reactions (e.g., food, drug, atopic reactions or asthmatic episodes) which, in the opinion of the investigator and sponsor, interfere with their ability to participate in the trial.
20. Subjects who have a history of malignancy.
21. Personal or family history of malignant hyperthermia.
22. Personal or family history of arrhythmias or ECG conductance abnormalities.
23. Subjects with a history of daily consumption of caffeine greater than 6 servings (40 mL each) from beverages (e.g., coffee, tea, soft drinks) and food stuffs (e.g., chocolate, ice cream, cookies) (45 gm each ).