The study evaluates the safety of IV tramadol managing post-operative pain following surgery.

(Non-clinical summary) Tramadol is a centrally-acting synthetic analgesic of the aminocyclohexanol group with opioidlike effects. Tramadol is extensively metabolized following administration, which results in a number of enantiomeric metabolites that display different opioid-receptor binding properties, and monoaminergic reuptake inhibition.

Inclusion Criteria:

• The patient is male or female 18-75 years of age
• Willing to give consent and able to understand the study procedures
• Female patients must be of non-childbearing potential or be practicing a highly effective contraption
• The patient must be willing to be housed in a healthcare facility and able to receive parenteral analgesia for at least 24 hours after surgery
• The patient meets definition of American Society of Anesthesiologists (ASA) Physical Class 1, or 2.

Exclusion Criteria:

• The patient has used chronic opioid therapy, defined as >= 20 MEQs of morphine per day >=3 days out of 7 days over the past 4 weeks.
• The patient has a recent (within 2 years) and/or current history of alcohol, opiate or tranquilizer abuse or dependence.
• The patient is taking herbal or dietary supplements or medications that are moderate or strong inhibitors of CYP2D6 or CYP3A4 (e.g., fluoxetine, paroxetine, amitriptyline, quinidine, ketoconazole, erythromycin, grapefruit juice) or inducers of CYP3A4 (e.g., carbamazepine, rifampin, St. John's Wort) and cannot go through a minimum washout period of 7 days prior to surgery.
• The patient has a history of epilepsy, is susceptible to seizures.
• The patient cannot be withdrawn from medications (at least 7 days prior to surgery) that may lower the seizure threshold (e.g. anti-psychotic agents, MAOI inhibitors) or which increase serotonergic tone (e.g. selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants, triptans, amphetamines).
• The patient has had a recent (within 6 months) cardiovascular event or clinically significant abnormal ECG finding at screening.
• The patient has a history of Long QT Syndrome or a relative with this condition.
• The patient has expressed suicidal ideation within the past 3 months or is considered to be at risk of suicide.
• The patient is morbidly obese (body mass index [BMI] ≥ 40 kg/m2) or has documented sleep apnea requiring CPAP or other treatment.
• Female patient is pregnant and/or undergoing a pregnancy-related surgery, or breastfeeding.
• The patient has a history of cardiopulmonary, neurological or psychiatric condition that may confound the assessments of efficacy or safety.
• The patient has cirrhosis, moderate or severe hepatic impairment or an alanine aminotransferase (ALT) or aspartate aminotransferase (AST) value > 3X upper limit of normal (ULN) at Screening.
• The patient has severe renal impairment or a serum creatinine value of > 2x upper limit of normal (ULN) at Screening.
• The patient has potassium, sodium, calcium or magnesium levels outside of the normal range at Screening.
• The patient has a hemoglobin level at screening which, in the judgment of the Investigator, is not suitable for participation in this study.

6 months