This is a randomized, double-blind, placebo-controlled, single ascending-dose study to investigate the effect of a single intravenous (IV) dose of SHR0410 at 6 dose levels (0.5 μg/kg, 1 μg/kg, 2 μg/kg, 5 μg/kg, 10 μg/kg and 20 μg/kg) in healthy participants.

Forty eight eligible participants will be enrolled into the 6 dose cohorts. For each cohort, a sentinel group of 2 subjects (1 receiving SHR0410 and 1 receiving placebo) will be dosed first (1:1 ratio). If no drug related adverse events occur in the sentinel participants, the remaining 6 subjects in a cohort will be dosed on the next day or later in a 5:1 ratio (5 subjects receiving SHR0410 and 1 subject receiving placebo). SHR0410 will be diluted in saline and administered as a 15 min constant dose IV infusion at a rate of 20 ml/hr on Day 1.

Inclusion Criteria:

1. Male between the ages of 18 and 45 years, inclusive.
2. Body mass index (BMI) of 18.0 to 30.0 kg/m2 and a total body weight of 50 kg to 125kg, inclusive.
3. Considered generally healthy upon completion of medical history, physical examination, vital signs, SpO2, laboratory parameters, and ECG, as judged by the Investigator.

Exclusion Criteria:

1. Known sensitivity to any of the components of the investigational product formulation, or any other opioids.
2. Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at time of dosing).
3. Any other medical or psychological condition, which in the opinion of the Investigator, might create undue risk to the participant or interfere with the participant's ability to comply with the protocol requirements, or to complete the study.